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Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6

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David Woodhouse 2010-04-09 15:17:41 +01:00
parent 0b8973a818 2eaa9cfdf3
commit 87d8a69709
9969 changed files with 671197 additions and 288345 deletions
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25
.gitignore vendored
View file

@ -22,6 +22,7 @@
*.lst
*.symtypes
*.order
modules.builtin
*.elf
*.bin
*.gz
@ -33,26 +34,26 @@
#
# Top-level generic files
#
tags
TAGS
vmlinux
System.map
Module.markers
Module.symvers
/tags
/TAGS
/linux
/vmlinux
/vmlinuz
/System.map
/Module.markers
/Module.symvers
#
# git files that we don't want to ignore even it they are dot-files
#
!.gitignore
!.mailmap
#
# Generated include files
#
include/asm
include/asm-*/asm-offsets.h
include/config
include/linux/autoconf.h
include/linux/compile.h
include/linux/version.h
include/linux/utsrelease.h
include/linux/bounds.h
include/generated
# stgit generated dirs

7
Documentation/ABI/stable/sysfs-devices-node Normal file
View file

@ -0,0 +1,7 @@
What: /sys/devices/system/node/nodeX
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
When CONFIG_NUMA is enabled, this is a directory containing
information on node X such as what CPUs are local to the
node.

12
Documentation/ABI/testing/ima_policy
View file

@ -20,7 +20,7 @@ Description:
lsm: [[subj_user=] [subj_role=] [subj_type=]
[obj_user=] [obj_role=] [obj_type=]]
base: func:= [BPRM_CHECK][FILE_MMAP][INODE_PERMISSION]
base: func:= [BPRM_CHECK][FILE_MMAP][FILE_CHECK]
mask:= [MAY_READ] [MAY_WRITE] [MAY_APPEND] [MAY_EXEC]
fsmagic:= hex value
uid:= decimal value
@ -40,11 +40,11 @@ Description:
measure func=BPRM_CHECK
measure func=FILE_MMAP mask=MAY_EXEC
measure func=INODE_PERM mask=MAY_READ uid=0
measure func=FILE_CHECK mask=MAY_READ uid=0
The default policy measures all executables in bprm_check,
all files mmapped executable in file_mmap, and all files
open for read by root in inode_permission.
open for read by root in do_filp_open.
Examples of LSM specific definitions:
@ -54,8 +54,8 @@ Description:
dont_measure obj_type=var_log_t
dont_measure obj_type=auditd_log_t
measure subj_user=system_u func=INODE_PERM mask=MAY_READ
measure subj_role=system_r func=INODE_PERM mask=MAY_READ
measure subj_user=system_u func=FILE_CHECK mask=MAY_READ
measure subj_role=system_r func=FILE_CHECK mask=MAY_READ
Smack:
measure subj_user=_ func=INODE_PERM mask=MAY_READ
measure subj_user=_ func=FILE_CHECK mask=MAY_READ

14
Documentation/ABI/testing/sysfs-block
View file

@ -128,3 +128,17 @@ Description:
preferred request size for workloads where sustained
throughput is desired. If no optimal I/O size is
reported this file contains 0.
What: /sys/block/<disk>/queue/nomerges
Date: January 2010
Contact:
Description:
Standard I/O elevator operations include attempts to
merge contiguous I/Os. For known random I/O loads these
attempts will always fail and result in extra cycles
being spent in the kernel. This allows one to turn off
this behavior on one of two ways: When set to 1, complex
merge checks are disabled, but the simple one-shot merges
with the previous I/O request are enabled. When set to 2,
all merge tries are disabled. The default value is 0 -
which enables all types of merge tries.

29
Documentation/ABI/testing/sysfs-bus-usb
View file

@ -21,25 +21,27 @@ Contact: Alan Stern <stern@rowland.harvard.edu>
Description:
Each USB device directory will contain a file named
power/level. This file holds a power-level setting for
the device, one of "on", "auto", or "suspend".
the device, either "on" or "auto".
"on" means that the device is not allowed to autosuspend,
although normal suspends for system sleep will still
be honored. "auto" means the device will autosuspend
and autoresume in the usual manner, according to the
capabilities of its driver. "suspend" means the device
is forced into a suspended state and it will not autoresume
in response to I/O requests. However remote-wakeup requests
from the device may still be enabled (the remote-wakeup
setting is controlled separately by the power/wakeup
attribute).
capabilities of its driver.
During normal use, devices should be left in the "auto"
level. The other levels are meant for administrative uses.
level. The "on" level is meant for administrative uses.
If you want to suspend a device immediately but leave it
free to wake up in response to I/O requests, you should
write "0" to power/autosuspend.
Device not capable of proper suspend and resume should be
left in the "on" level. Although the USB spec requires
devices to support suspend/resume, many of them do not.
In fact so many don't that by default, the USB core
initializes all non-hub devices in the "on" level. Some
drivers may change this setting when they are bound.
What: /sys/bus/usb/devices/.../power/persist
Date: May 2007
KernelVersion: 2.6.23
@ -157,3 +159,14 @@ Description:
device. This is useful to ensure auto probing won't
match the driver to the device. For example:
# echo "046d c315" > /sys/bus/usb/drivers/foo/remove_id
What: /sys/bus/usb/device/.../avoid_reset_quirk
Date: December 2009
Contact: Oliver Neukum <oliver@neukum.org>
Description:
Writing 1 to this file tells the kernel that this
device will morph into another mode when it is reset.
Drivers will not use reset for error handling for
such devices.
Users:
usb_modeswitch

79
Documentation/ABI/testing/sysfs-devices-power Normal file
View file

@ -0,0 +1,79 @@
What: /sys/devices/.../power/
Date: January 2009
Contact: Rafael J. Wysocki <rjw@sisk.pl>
Description:
The /sys/devices/.../power directory contains attributes
allowing the user space to check and modify some power
management related properties of given device.
What: /sys/devices/.../power/wakeup
Date: January 2009
Contact: Rafael J. Wysocki <rjw@sisk.pl>
Description:
The /sys/devices/.../power/wakeup attribute allows the user
space to check if the device is enabled to wake up the system
from sleep states, such as the memory sleep state (suspend to
RAM) and hibernation (suspend to disk), and to enable or disable
it to do that as desired.
Some devices support "wakeup" events, which are hardware signals
used to activate the system from a sleep state. Such devices
have one of the following two values for the sysfs power/wakeup
file:
+ "enabled\n" to issue the events;
+ "disabled\n" not to do so;
In that cases the user space can change the setting represented
by the contents of this file by writing either "enabled", or
"disabled" to it.
For the devices that are not capable of generating system wakeup
events this file contains "\n". In that cases the user space
cannot modify the contents of this file and the device cannot be
enabled to wake up the system.
What: /sys/devices/.../power/control
Date: January 2009
Contact: Rafael J. Wysocki <rjw@sisk.pl>
Description:
The /sys/devices/.../power/control attribute allows the user
space to control the run-time power management of the device.
All devices have one of the following two values for the
power/control file:
+ "auto\n" to allow the device to be power managed at run time;
+ "on\n" to prevent the device from being power managed;
The default for all devices is "auto", which means that they may
be subject to automatic power management, depending on their
drivers. Changing this attribute to "on" prevents the driver
from power managing the device at run time. Doing that while
the device is suspended causes it to be woken up.
What: /sys/devices/.../power/async
Date: January 2009
Contact: Rafael J. Wysocki <rjw@sisk.pl>
Description:
The /sys/devices/.../async attribute allows the user space to
enable or diasble the device's suspend and resume callbacks to
be executed asynchronously (ie. in separate threads, in parallel
with the main suspend/resume thread) during system-wide power
transitions (eg. suspend to RAM, hibernation).
All devices have one of the following two values for the
power/async file:
+ "enabled\n" to permit the asynchronous suspend/resume;
+ "disabled\n" to forbid it;
The value of this attribute may be changed by writing either
"enabled", or "disabled" to it.
It generally is unsafe to permit the asynchronous suspend/resume
of a device unless it is certain that all of the PM dependencies
of the device are known to the PM core. However, for some
devices this attribute is set to "enabled" by bus type code or
device drivers and in that cases it should be safe to leave the
default value.

44
Documentation/ABI/testing/sysfs-memory-page-offline Normal file
View file

@ -0,0 +1,44 @@
What: /sys/devices/system/memory/soft_offline_page
Date: Sep 2009
KernelVersion: 2.6.33
Contact: andi@firstfloor.org
Description:
Soft-offline the memory page containing the physical address
written into this file. Input is a hex number specifying the
physical address of the page. The kernel will then attempt
to soft-offline it, by moving the contents elsewhere or
dropping it if possible. The kernel will then be placed
on the bad page list and never be reused.
The offlining is done in kernel specific granuality.
Normally it's the base page size of the kernel, but
this might change.
The page must be still accessible, not poisoned. The
kernel will never kill anything for this, but rather
fail the offline. Return value is the size of the
number, or a error when the offlining failed. Reading
the file is not allowed.
What: /sys/devices/system/memory/hard_offline_page
Date: Sep 2009
KernelVersion: 2.6.33
Contact: andi@firstfloor.org
Description:
Hard-offline the memory page containing the physical
address written into this file. Input is a hex number
specifying the physical address of the page. The
kernel will then attempt to hard-offline the page, by
trying to drop the page or killing any owner or
triggering IO errors if needed. Note this may kill
any processes owning the page. The kernel will avoid
to access this page assuming it's poisoned by the
hardware.
The offlining is done in kernel specific granuality.
Normally it's the base page size of the kernel, but
this might change.
Return value is the size of the number, or a error when
the offlining failed.
Reading the file is not allowed.

12
Documentation/ABI/testing/sysfs-platform-asus-laptop
View file

@ -1,4 +1,4 @@
What: /sys/devices/platform/asus-laptop/display
What: /sys/devices/platform/asus_laptop/display
Date: January 2007
KernelVersion: 2.6.20
Contact: "Corentin Chary" <corentincj@iksaif.net>
@ -13,7 +13,7 @@ Description:
Ex: - 0 (0000b) means no display
- 3 (0011b) CRT+LCD.
What: /sys/devices/platform/asus-laptop/gps
What: /sys/devices/platform/asus_laptop/gps
Date: January 2007
KernelVersion: 2.6.20
Contact: "Corentin Chary" <corentincj@iksaif.net>
@ -21,7 +21,7 @@ Description:
Control the gps device. 1 means on, 0 means off.
Users: Lapsus
What: /sys/devices/platform/asus-laptop/ledd
What: /sys/devices/platform/asus_laptop/ledd
Date: January 2007
KernelVersion: 2.6.20
Contact: "Corentin Chary" <corentincj@iksaif.net>
@ -29,11 +29,11 @@ Description:
Some models like the W1N have a LED display that can be
used to display several informations.
To control the LED display, use the following :
echo 0x0T000DDD > /sys/devices/platform/asus-laptop/
echo 0x0T000DDD > /sys/devices/platform/asus_laptop/
where T control the 3 letters display, and DDD the 3 digits display.
The DDD table can be found in Documentation/laptops/asus-laptop.txt
What: /sys/devices/platform/asus-laptop/bluetooth
What: /sys/devices/platform/asus_laptop/bluetooth
Date: January 2007
KernelVersion: 2.6.20
Contact: "Corentin Chary" <corentincj@iksaif.net>
@ -42,7 +42,7 @@ Description:
This may control the led, the device or both.
Users: Lapsus
What: /sys/devices/platform/asus-laptop/wlan
What: /sys/devices/platform/asus_laptop/wlan
Date: January 2007
KernelVersion: 2.6.20
Contact: "Corentin Chary" <corentincj@iksaif.net>

10
Documentation/ABI/testing/sysfs-platform-eeepc-laptop
View file

@ -1,4 +1,4 @@
What: /sys/devices/platform/eeepc-laptop/disp
What: /sys/devices/platform/eeepc/disp
Date: May 2008
KernelVersion: 2.6.26
Contact: "Corentin Chary" <corentincj@iksaif.net>
@ -9,21 +9,21 @@ Description:
- 3 = LCD+CRT
If you run X11, you should use xrandr instead.
What: /sys/devices/platform/eeepc-laptop/camera
What: /sys/devices/platform/eeepc/camera
Date: May 2008
KernelVersion: 2.6.26
Contact: "Corentin Chary" <corentincj@iksaif.net>
Description:
Control the camera. 1 means on, 0 means off.
What: /sys/devices/platform/eeepc-laptop/cardr
What: /sys/devices/platform/eeepc/cardr
Date: May 2008
KernelVersion: 2.6.26
Contact: "Corentin Chary" <corentincj@iksaif.net>
Description:
Control the card reader. 1 means on, 0 means off.
What: /sys/devices/platform/eeepc-laptop/cpufv
What: /sys/devices/platform/eeepc/cpufv
Date: Jun 2009
KernelVersion: 2.6.31
Contact: "Corentin Chary" <corentincj@iksaif.net>
@ -42,7 +42,7 @@ Description:
`------------ Availables modes
For example, 0x301 means: mode 1 selected, 3 available modes.
What: /sys/devices/platform/eeepc-laptop/available_cpufv
What: /sys/devices/platform/eeepc/available_cpufv
Date: Jun 2009
KernelVersion: 2.6.31
Contact: "Corentin Chary" <corentincj@iksaif.net>

13
Documentation/ABI/testing/sysfs-power
View file

@ -101,3 +101,16 @@ Description:
CAUTION: Using it will cause your machine's real-time (CMOS)
clock to be set to a random invalid time after a resume.
What: /sys/power/pm_async
Date: January 2009
Contact: Rafael J. Wysocki <rjw@sisk.pl>
Description:
The /sys/power/pm_async file controls the switch allowing the
user space to enable or disable asynchronous suspend and resume
of devices. If enabled, this feature will cause some device
drivers' suspend and resume callbacks to be executed in parallel
with each other and with the main suspend thread. It is enabled
if this file contains "1", which is the default. It may be
disabled by writing "0" to this file, in which case all devices
will be suspended and resumed synchronously.

2
Documentation/Changes
View file

@ -49,6 +49,8 @@ o oprofile 0.9 # oprofiled --version
o udev 081 # udevinfo -V
o grub 0.93 # grub --version
o mcelog 0.6
o iptables 1.4.1 # iptables -V
Kernel compilation
==================

344
Documentation/DMA-mapping.txt → Documentation/DMA-API-HOWTO.txt
View file

@ -1,12 +1,12 @@
Dynamic DMA mapping
===================
Dynamic DMA mapping Guide
=========================
David S. Miller <davem@redhat.com>
Richard Henderson <rth@cygnus.com>
Jakub Jelinek <jakub@redhat.com>
This document describes the DMA mapping system in terms of the pci_
API. For a similar API that works for generic devices, see
This is a guide to device driver writers on how to use the DMA API
with example pseudo-code. For a concise description of the API, see
DMA-API.txt.
Most of the 64bit platforms have special hardware that translates bus
@ -26,12 +26,15 @@ mapped only for the time they are actually used and unmapped after the DMA
transfer.
The following API will work of course even on platforms where no such
hardware exists, see e.g. arch/x86/include/asm/pci.h for how it is implemented on
top of the virt_to_bus interface.
hardware exists.
Note that the DMA API works with any bus independent of the underlying
microprocessor architecture. You should use the DMA API rather than
the bus specific DMA API (e.g. pci_dma_*).
First of all, you should make sure
#include <linux/pci.h>
#include <linux/dma-mapping.h>
is in your driver. This file will obtain for you the definition of the
dma_addr_t (which can hold any valid DMA address for the platform)
@ -78,44 +81,43 @@ for you to DMA from/to.
DMA addressing limitations
Does your device have any DMA addressing limitations? For example, is
your device only capable of driving the low order 24-bits of address
on the PCI bus for SAC DMA transfers? If so, you need to inform the
PCI layer of this fact.
your device only capable of driving the low order 24-bits of address?
If so, you need to inform the kernel of this fact.
By default, the kernel assumes that your device can address the full
32-bits in a SAC cycle. For a 64-bit DAC capable device, this needs
to be increased. And for a device with limitations, as discussed in
the previous paragraph, it needs to be decreased.
32-bits. For a 64-bit capable device, this needs to be increased.
And for a device with limitations, as discussed in the previous
paragraph, it needs to be decreased.
pci_alloc_consistent() by default will return 32-bit DMA addresses.
PCI-X specification requires PCI-X devices to support 64-bit
addressing (DAC) for all transactions. And at least one platform (SGI
SN2) requires 64-bit consistent allocations to operate correctly when
the IO bus is in PCI-X mode. Therefore, like with pci_set_dma_mask(),
it's good practice to call pci_set_consistent_dma_mask() to set the
appropriate mask even if your device only supports 32-bit DMA
(default) and especially if it's a PCI-X device.
Special note about PCI: PCI-X specification requires PCI-X devices to
support 64-bit addressing (DAC) for all transactions. And at least
one platform (SGI SN2) requires 64-bit consistent allocations to
operate correctly when the IO bus is in PCI-X mode.
For correct operation, you must interrogate the PCI layer in your
device probe routine to see if the PCI controller on the machine can
properly support the DMA addressing limitation your device has. It is
good style to do this even if your device holds the default setting,
For correct operation, you must interrogate the kernel in your device
probe routine to see if the DMA controller on the machine can properly
support the DMA addressing limitation your device has. It is good
style to do this even if your device holds the default setting,
because this shows that you did think about these issues wrt. your
device.
The query is performed via a call to pci_set_dma_mask():
The query is performed via a call to dma_set_mask():
int pci_set_dma_mask(struct pci_dev *pdev, u64 device_mask);
int dma_set_mask(struct device *dev, u64 mask);
The query for consistent allocations is performed via a call to
pci_set_consistent_dma_mask():
dma_set_coherent_mask():
int pci_set_consistent_dma_mask(struct pci_dev *pdev, u64 device_mask);
int dma_set_coherent_mask(struct device *dev, u64 mask);
Here, pdev is a pointer to the PCI device struct of your device, and
device_mask is a bit mask describing which bits of a PCI address your
device supports. It returns zero if your card can perform DMA
properly on the machine given the address mask you provided.
Here, dev is a pointer to the device struct of your device, and mask
is a bit mask describing which bits of an address your device
supports. It returns zero if your card can perform DMA properly on
the machine given the address mask you provided. In general, the
device struct of your device is embedded in the bus specific device
struct of your device. For example, a pointer to the device struct of
your PCI device is pdev->dev (pdev is a pointer to the PCI device
struct of your device).
If it returns non-zero, your device cannot perform DMA properly on
this platform, and attempting to do so will result in undefined
@ -133,31 +135,30 @@ of your driver reports that performance is bad or that the device is not
even detected, you can ask them for the kernel messages to find out
exactly why.
The standard 32-bit addressing PCI device would do something like
this:
The standard 32-bit addressing device would do something like this:
if (pci_set_dma_mask(pdev, DMA_BIT_MASK(32))) {
if (dma_set_mask(dev, DMA_BIT_MASK(32))) {
printk(KERN_WARNING
"mydev: No suitable DMA available.\n");
goto ignore_this_device;
}
Another common scenario is a 64-bit capable device. The approach
here is to try for 64-bit DAC addressing, but back down to a
32-bit mask should that fail. The PCI platform code may fail the
64-bit mask not because the platform is not capable of 64-bit
addressing. Rather, it may fail in this case simply because
32-bit SAC addressing is done more efficiently than DAC addressing.
Sparc64 is one platform which behaves in this way.
Another common scenario is a 64-bit capable device. The approach here
is to try for 64-bit addressing, but back down to a 32-bit mask that
should not fail. The kernel may fail the 64-bit mask not because the
platform is not capable of 64-bit addressing. Rather, it may fail in
this case simply because 32-bit addressing is done more efficiently
than 64-bit addressing. For example, Sparc64 PCI SAC addressing is
more efficient than DAC addressing.
Here is how you would handle a 64-bit capable device which can drive
all 64-bits when accessing streaming DMA:
int using_dac;
if (!pci_set_dma_mask(pdev, DMA_BIT_MASK(64))) {
if (!dma_set_mask(dev, DMA_BIT_MASK(64))) {
using_dac = 1;
} else if (!pci_set_dma_mask(pdev, DMA_BIT_MASK(32))) {
} else if (!dma_set_mask(dev, DMA_BIT_MASK(32))) {
using_dac = 0;
} else {
printk(KERN_WARNING
@ -170,36 +171,36 @@ the case would look like this:
int using_dac, consistent_using_dac;
if (!pci_set_dma_mask(pdev, DMA_BIT_MASK(64))) {
if (!dma_set_mask(dev, DMA_BIT_MASK(64))) {
using_dac = 1;
consistent_using_dac = 1;
pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(64));
} else if (!pci_set_dma_mask(pdev, DMA_BIT_MASK(32))) {
dma_set_coherent_mask(dev, DMA_BIT_MASK(64));
} else if (!dma_set_mask(dev, DMA_BIT_MASK(32))) {
using_dac = 0;
consistent_using_dac = 0;
pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(32));
dma_set_coherent_mask(dev, DMA_BIT_MASK(32));
} else {
printk(KERN_WARNING
"mydev: No suitable DMA available.\n");
goto ignore_this_device;
}
pci_set_consistent_dma_mask() will always be able to set the same or a
smaller mask as pci_set_dma_mask(). However for the rare case that a
dma_set_coherent_mask() will always be able to set the same or a
smaller mask as dma_set_mask(). However for the rare case that a
device driver only uses consistent allocations, one would have to
check the return value from pci_set_consistent_dma_mask().
check the return value from dma_set_coherent_mask().
Finally, if your device can only drive the low 24-bits of
address during PCI bus mastering you might do something like:
address you might do something like:
if (pci_set_dma_mask(pdev, DMA_BIT_MASK(24))) {
if (dma_set_mask(dev, DMA_BIT_MASK(24))) {
printk(KERN_WARNING
"mydev: 24-bit DMA addressing not available.\n");
goto ignore_this_device;
}
When pci_set_dma_mask() is successful, and returns zero, the PCI layer
saves away this mask you have provided. The PCI layer will use this
When dma_set_mask() is successful, and returns zero, the kernel saves
away this mask you have provided. The kernel will use this
information later when you make DMA mappings.
There is a case which we are aware of at this time, which is worth
@ -208,7 +209,7 @@ functions (for example a sound card provides playback and record
functions) and the various different functions have _different_
DMA addressing limitations, you may wish to probe each mask and
only provide the functionality which the machine can handle. It
is important that the last call to pci_set_dma_mask() be for the
is important that the last call to dma_set_mask() be for the
most specific mask.
Here is pseudo-code showing how this might be done:
@ -217,17 +218,17 @@ Here is pseudo-code showing how this might be done:
#define RECORD_ADDRESS_BITS DMA_BIT_MASK(24)
struct my_sound_card *card;
struct pci_dev *pdev;
struct device *dev;
...
if (!pci_set_dma_mask(pdev, PLAYBACK_ADDRESS_BITS)) {
if (!dma_set_mask(dev, PLAYBACK_ADDRESS_BITS)) {
card->playback_enabled = 1;
} else {
card->playback_enabled = 0;
printk(KERN_WARNING "%s: Playback disabled due to DMA limitations.\n",
card->name);
}
if (!pci_set_dma_mask(pdev, RECORD_ADDRESS_BITS)) {
if (!dma_set_mask(dev, RECORD_ADDRESS_BITS)) {
card->record_enabled = 1;
} else {
card->record_enabled = 0;
@ -252,8 +253,8 @@ There are two types of DMA mappings:
Think of "consistent" as "synchronous" or "coherent".
The current default is to return consistent memory in the low 32
bits of the PCI bus space. However, for future compatibility you
should set the consistent mask even if this default is fine for your
bits of the bus space. However, for future compatibility you should
set the consistent mask even if this default is fine for your
driver.
Good examples of what to use consistent mappings for are:
@ -285,9 +286,9 @@ There are two types of DMA mappings:
found in PCI bridges (such as by reading a register's value
after writing it).
- Streaming DMA mappings which are usually mapped for one DMA transfer,
unmapped right after it (unless you use pci_dma_sync_* below) and for which
hardware can optimize for sequential accesses.
- Streaming DMA mappings which are usually mapped for one DMA
transfer, unmapped right after it (unless you use dma_sync_* below)
and for which hardware can optimize for sequential accesses.
This of "streaming" as "asynchronous" or "outside the coherency
domain".
@ -302,8 +303,8 @@ There are two types of DMA mappings:
optimizations the hardware allows. To this end, when using
such mappings you must be explicit about what you want to happen.
Neither type of DMA mapping has alignment restrictions that come
from PCI, although some devices may have such restrictions.
Neither type of DMA mapping has alignment restrictions that come from
the underlying bus, although some devices may have such restrictions.
Also, systems with caches that aren't DMA-coherent will work better
when the underlying buffers don't share cache lines with other data.
@ -315,33 +316,27 @@ you should do:
dma_addr_t dma_handle;
cpu_addr = pci_alloc_consistent(pdev, size, &dma_handle);
cpu_addr = dma_alloc_coherent(dev, size, &dma_handle, gfp);
where pdev is a struct pci_dev *. This may be called in interrupt context.
You should use dma_alloc_coherent (see DMA-API.txt) for buses
where devices don't have struct pci_dev (like ISA, EISA).
This argument is needed because the DMA translations may be bus
specific (and often is private to the bus which the device is attached
to).
where device is a struct device *. This may be called in interrupt
context with the GFP_ATOMIC flag.
Size is the length of the region you want to allocate, in bytes.
This routine will allocate RAM for that region, so it acts similarly to
__get_free_pages (but takes size instead of a page order). If your
driver needs regions sized smaller than a page, you may prefer using
the pci_pool interface, described below.
the dma_pool interface, described below.
The consistent DMA mapping interfaces, for non-NULL pdev, will by
default return a DMA address which is SAC (Single Address Cycle)
addressable. Even if the device indicates (via PCI dma mask) that it
may address the upper 32-bits and thus perform DAC cycles, consistent
allocation will only return > 32-bit PCI addresses for DMA if the
consistent dma mask has been explicitly changed via
pci_set_consistent_dma_mask(). This is true of the pci_pool interface
as well.
The consistent DMA mapping interfaces, for non-NULL dev, will by
default return a DMA address which is 32-bit addressable. Even if the
device indicates (via DMA mask) that it may address the upper 32-bits,
consistent allocation will only return > 32-bit addresses for DMA if
the consistent DMA mask has been explicitly changed via
dma_set_coherent_mask(). This is true of the dma_pool interface as
well.
pci_alloc_consistent returns two values: the virtual address which you
dma_alloc_coherent returns two values: the virtual address which you
can use to access it from the CPU and dma_handle which you pass to the
card.
@ -354,54 +349,54 @@ buffer you receive will not cross a 64K boundary.
To unmap and free such a DMA region, you call:
pci_free_consistent(pdev, size, cpu_addr, dma_handle);
dma_free_coherent(dev, size, cpu_addr, dma_handle);
where pdev, size are the same as in the above call and cpu_addr and
dma_handle are the values pci_alloc_consistent returned to you.
where dev, size are the same as in the above call and cpu_addr and
dma_handle are the values dma_alloc_coherent returned to you.
This function may not be called in interrupt context.
If your driver needs lots of smaller memory regions, you can write
custom code to subdivide pages returned by pci_alloc_consistent,
or you can use the pci_pool API to do that. A pci_pool is like
a kmem_cache, but it uses pci_alloc_consistent not __get_free_pages.
custom code to subdivide pages returned by dma_alloc_coherent,
or you can use the dma_pool API to do that. A dma_pool is like
a kmem_cache, but it uses dma_alloc_coherent not __get_free_pages.
Also, it understands common hardware constraints for alignment,
like queue heads needing to be aligned on N byte boundaries.
Create a pci_pool like this:
Create a dma_pool like this:
struct pci_pool *pool;
struct dma_pool *pool;
pool = pci_pool_create(name, pdev, size, align, alloc);
pool = dma_pool_create(name, dev, size, align, alloc);
The "name" is for diagnostics (like a kmem_cache name); pdev and size
The "name" is for diagnostics (like a kmem_cache name); dev and size
are as above. The device's hardware alignment requirement for this
type of data is "align" (which is expressed in bytes, and must be a
power of two). If your device has no boundary crossing restrictions,
pass 0 for alloc; passing 4096 says memory allocated from this pool
must not cross 4KByte boundaries (but at that time it may be better to
go for pci_alloc_consistent directly instead).
go for dma_alloc_coherent directly instead).
Allocate memory from a pci pool like this:
Allocate memory from a dma pool like this:
cpu_addr = pci_pool_alloc(pool, flags, &dma_handle);
cpu_addr = dma_pool_alloc(pool, flags, &dma_handle);
flags are SLAB_KERNEL if blocking is permitted (not in_interrupt nor
holding SMP locks), SLAB_ATOMIC otherwise. Like pci_alloc_consistent,
holding SMP locks), SLAB_ATOMIC otherwise. Like dma_alloc_coherent,
this returns two values, cpu_addr and dma_handle.
Free memory that was allocated from a pci_pool like this:
Free memory that was allocated from a dma_pool like this:
pci_pool_free(pool, cpu_addr, dma_handle);
dma_pool_free(pool, cpu_addr, dma_handle);
where pool is what you passed to pci_pool_alloc, and cpu_addr and
dma_handle are the values pci_pool_alloc returned. This function
where pool is what you passed to dma_pool_alloc, and cpu_addr and
dma_handle are the values dma_pool_alloc returned. This function
may be called in interrupt context.
Destroy a pci_pool by calling:
Destroy a dma_pool by calling:
pci_pool_destroy(pool);
dma_pool_destroy(pool);
Make sure you've called pci_pool_free for all memory allocated
Make sure you've called dma_pool_free for all memory allocated
from a pool before you destroy the pool. This function may not
be called in interrupt context.
@ -411,15 +406,15 @@ The interfaces described in subsequent portions of this document
take a DMA direction argument, which is an integer and takes on
one of the following values:
PCI_DMA_BIDIRECTIONAL
PCI_DMA_TODEVICE
PCI_DMA_FROMDEVICE
PCI_DMA_NONE
DMA_BIDIRECTIONAL
DMA_TO_DEVICE
DMA_FROM_DEVICE
DMA_NONE
One should provide the exact DMA direction if you know it.
PCI_DMA_TODEVICE means "from main memory to the PCI device"
PCI_DMA_FROMDEVICE means "from the PCI device to main memory"
DMA_TO_DEVICE means "from main memory to the device"
DMA_FROM_DEVICE means "from the device to main memory"
It is the direction in which the data moves during the DMA
transfer.
@ -427,12 +422,12 @@ You are _strongly_ encouraged to specify this as precisely
as you possibly can.
If you absolutely cannot know the direction of the DMA transfer,
specify PCI_DMA_BIDIRECTIONAL. It means that the DMA can go in
specify DMA_BIDIRECTIONAL. It means that the DMA can go in
either direction. The platform guarantees that you may legally
specify this, and that it will work, but this may be at the
cost of performance for example.
The value PCI_DMA_NONE is to be used for debugging. One can
The value DMA_NONE is to be used for debugging. One can
hold this in a data structure before you come to know the
precise direction, and this will help catch cases where your
direction tracking logic has failed to set things up properly.
@ -442,21 +437,21 @@ potential platform-specific optimizations of such) is for debugging.
Some platforms actually have a write permission boolean which DMA
mappings can be marked with, much like page protections in the user
program address space. Such platforms can and do report errors in the
kernel logs when the PCI controller hardware detects violation of the
kernel logs when the DMA controller hardware detects violation of the
permission setting.
Only streaming mappings specify a direction, consistent mappings
implicitly have a direction attribute setting of
PCI_DMA_BIDIRECTIONAL.
DMA_BIDIRECTIONAL.
The SCSI subsystem tells you the direction to use in the
'sc_data_direction' member of the SCSI command your driver is
working on.
For Networking drivers, it's a rather simple affair. For transmit
packets, map/unmap them with the PCI_DMA_TODEVICE direction
packets, map/unmap them with the DMA_TO_DEVICE direction
specifier. For receive packets, just the opposite, map/unmap them
with the PCI_DMA_FROMDEVICE direction specifier.
with the DMA_FROM_DEVICE direction specifier.
Using Streaming DMA mappings
@ -467,43 +462,43 @@ scatterlist.
To map a single region, you do:
struct pci_dev *pdev = mydev->pdev;
struct device *dev = &my_dev->dev;
dma_addr_t dma_handle;
void *addr = buffer->ptr;
size_t size = buffer->len;
dma_handle = pci_map_single(pdev, addr, size, direction);
dma_handle = dma_map_single(dev, addr, size, direction);
and to unmap it:
pci_unmap_single(pdev, dma_handle, size, direction);
dma_unmap_single(dev, dma_handle, size, direction);
You should call pci_unmap_single when the DMA activity is finished, e.g.
You should call dma_unmap_single when the DMA activity is finished, e.g.
from the interrupt which told you that the DMA transfer is done.
Using cpu pointers like this for single mappings has a disadvantage,
you cannot reference HIGHMEM memory in this way. Thus, there is a
map/unmap interface pair akin to pci_{map,unmap}_single. These
map/unmap interface pair akin to dma_{map,unmap}_single. These
interfaces deal with page/offset pairs instead of cpu pointers.
Specifically:
struct pci_dev *pdev = mydev->pdev;
struct device *dev = &my_dev->dev;
dma_addr_t dma_handle;
struct page *page = buffer->page;
unsigned long offset = buffer->offset;
size_t size = buffer->len;
dma_handle = pci_map_page(pdev, page, offset, size, direction);
dma_handle = dma_map_page(dev, page, offset, size, direction);
...
pci_unmap_page(pdev, dma_handle, size, direction);
dma_unmap_page(dev, dma_handle, size, direction);
Here, "offset" means byte offset within the given page.
With scatterlists, you map a region gathered from several regions by:
int i, count = pci_map_sg(pdev, sglist, nents, direction);
int i, count = dma_map_sg(dev, sglist, nents, direction);
struct scatterlist *sg;
for_each_sg(sglist, sg, count, i) {
@ -527,16 +522,16 @@ accessed sg->address and sg->length as shown above.
To unmap a scatterlist, just call:
pci_unmap_sg(pdev, sglist, nents, direction);
dma_unmap_sg(dev, sglist, nents, direction);
Again, make sure DMA activity has already finished.
PLEASE NOTE: The 'nents' argument to the pci_unmap_sg call must be
the _same_ one you passed into the pci_map_sg call,
PLEASE NOTE: The 'nents' argument to the dma_unmap_sg call must be
the _same_ one you passed into the dma_map_sg call,
it should _NOT_ be the 'count' value _returned_ from the
pci_map_sg call.
dma_map_sg call.
Every pci_map_{single,sg} call should have its pci_unmap_{single,sg}
Every dma_map_{single,sg} call should have its dma_unmap_{single,sg}
counterpart, because the bus address space is a shared resource (although
in some ports the mapping is per each BUS so less devices contend for the
same bus address space) and you could render the machine unusable by eating
@ -547,14 +542,14 @@ the data in between the DMA transfers, the buffer needs to be synced
properly in order for the cpu and device to see the most uptodate and
correct copy of the DMA buffer.
So, firstly, just map it with pci_map_{single,sg}, and after each DMA
So, firstly, just map it with dma_map_{single,sg}, and after each DMA
transfer call either:
pci_dma_sync_single_for_cpu(pdev, dma_handle, size, direction);
dma_sync_single_for_cpu(dev, dma_handle, size, direction);
or:
pci_dma_sync_sg_for_cpu(pdev, sglist, nents, direction);
dma_sync_sg_for_cpu(dev, sglist, nents, direction);
as appropriate.
@ -562,27 +557,27 @@ Then, if you wish to let the device get at the DMA area again,
finish accessing the data with the cpu, and then before actually
giving the buffer to the hardware call either:
pci_dma_sync_single_for_device(pdev, dma_handle, size, direction);
dma_sync_single_for_device(dev, dma_handle, size, direction);
or:
pci_dma_sync_sg_for_device(dev, sglist, nents, direction);
dma_sync_sg_for_device(dev, sglist, nents, direction);
as appropriate.
After the last DMA transfer call one of the DMA unmap routines
pci_unmap_{single,sg}. If you don't touch the data from the first pci_map_*
call till pci_unmap_*, then you don't have to call the pci_dma_sync_*
dma_unmap_{single,sg}. If you don't touch the data from the first dma_map_*
call till dma_unmap_*, then you don't have to call the dma_sync_*
routines at all.
Here is pseudo code which shows a situation in which you would need
to use the pci_dma_sync_*() interfaces.
to use the dma_sync_*() interfaces.
my_card_setup_receive_buffer(struct my_card *cp, char *buffer, int len)
{
dma_addr_t mapping;
mapping = pci_map_single(cp->pdev, buffer, len, PCI_DMA_FROMDEVICE);
mapping = dma_map_single(cp->dev, buffer, len, DMA_FROM_DEVICE);
cp->rx_buf = buffer;
cp->rx_len = len;
@ -606,25 +601,25 @@ to use the pci_dma_sync_*() interfaces.
* the DMA transfer with the CPU first
* so that we see updated contents.
*/
pci_dma_sync_single_for_cpu(cp->pdev, cp->rx_dma,
cp->rx_len,
PCI_DMA_FROMDEVICE);
dma_sync_single_for_cpu(&cp->dev, cp->rx_dma,
cp->rx_len,
DMA_FROM_DEVICE);
/* Now it is safe to examine the buffer. */
hp = (struct my_card_header *) cp->rx_buf;
if (header_is_ok(hp)) {
pci_unmap_single(cp->pdev, cp->rx_dma, cp->rx_len,
PCI_DMA_FROMDEVICE);
dma_unmap_single(&cp->dev, cp->rx_dma, cp->rx_len,
DMA_FROM_DEVICE);
pass_to_upper_layers(cp->rx_buf);
make_and_setup_new_rx_buf(cp);
} else {
/* Just sync the buffer and give it back
* to the card.
*/
pci_dma_sync_single_for_device(cp->pdev,
cp->rx_dma,
cp->rx_len,
PCI_DMA_FROMDEVICE);
dma_sync_single_for_device(&cp->dev,
cp->rx_dma,
cp->rx_len,
DMA_FROM_DEVICE);
give_rx_buf_to_card(cp);
}
}
@ -634,19 +629,19 @@ Drivers converted fully to this interface should not use virt_to_bus any
longer, nor should they use bus_to_virt. Some drivers have to be changed a
little bit, because there is no longer an equivalent to bus_to_virt in the
dynamic DMA mapping scheme - you have to always store the DMA addresses
returned by the pci_alloc_consistent, pci_pool_alloc, and pci_map_single
calls (pci_map_sg stores them in the scatterlist itself if the platform
returned by the dma_alloc_coherent, dma_pool_alloc, and dma_map_single
calls (dma_map_sg stores them in the scatterlist itself if the platform
supports dynamic DMA mapping in hardware) in your driver structures and/or
in the card registers.
All PCI drivers should be using these interfaces with no exceptions.
It is planned to completely remove virt_to_bus() and bus_to_virt() as
All drivers should be using these interfaces with no exceptions. It
is planned to completely remove virt_to_bus() and bus_to_virt() as
they are entirely deprecated. Some ports already do not provide these
as it is impossible to correctly support them.
Optimizing Unmap State Space Consumption
On many platforms, pci_unmap_{single,page}() is simply a nop.
On many platforms, dma_unmap_{single,page}() is simply a nop.
Therefore, keeping track of the mapping address and length is a waste
of space. Instead of filling your drivers up with ifdefs and the like
to "work around" this (which would defeat the whole purpose of a
@ -655,7 +650,7 @@ portable API) the following facilities are provided.
Actually, instead of describing the macros one by one, we'll
transform some example code.
1) Use DECLARE_PCI_UNMAP_{ADDR,LEN} in state saving structures.
1) Use DEFINE_DMA_UNMAP_{ADDR,LEN} in state saving structures.
Example, before:
struct ring_state {
@ -668,14 +663,11 @@ transform some example code.
struct ring_state {
struct sk_buff *skb;
DECLARE_PCI_UNMAP_ADDR(mapping)
DECLARE_PCI_UNMAP_LEN(len)
DEFINE_DMA_UNMAP_ADDR(mapping);
DEFINE_DMA_UNMAP_LEN(len);
};
NOTE: DO NOT put a semicolon at the end of the DECLARE_*()
macro.
2) Use pci_unmap_{addr,len}_set to set these values.
2) Use dma_unmap_{addr,len}_set to set these values.
Example, before:
ringp->mapping = FOO;
@ -683,21 +675,21 @@ transform some example code.
after:
pci_unmap_addr_set(ringp, mapping, FOO);
pci_unmap_len_set(ringp, len, BAR);
dma_unmap_addr_set(ringp, mapping, FOO);
dma_unmap_len_set(ringp, len, BAR);
3) Use pci_unmap_{addr,len} to access these values.
3) Use dma_unmap_{addr,len} to access these values.
Example, before:
pci_unmap_single(pdev, ringp->mapping, ringp->len,
PCI_DMA_FROMDEVICE);
dma_unmap_single(dev, ringp->mapping, ringp->len,
DMA_FROM_DEVICE);
after:
pci_unmap_single(pdev,
pci_unmap_addr(ringp, mapping),
pci_unmap_len(ringp, len),
PCI_DMA_FROMDEVICE);
dma_unmap_single(dev,
dma_unmap_addr(ringp, mapping),
dma_unmap_len(ringp, len),
DMA_FROM_DEVICE);
It really should be self-explanatory. We treat the ADDR and LEN
separately, because it is possible for an implementation to only
@ -732,15 +724,15 @@ to "Closing".
DMA address space is limited on some architectures and an allocation
failure can be determined by:
- checking if pci_alloc_consistent returns NULL or pci_map_sg returns 0
- checking if dma_alloc_coherent returns NULL or dma_map_sg returns 0
- checking the returned dma_addr_t of pci_map_single and pci_map_page
by using pci_dma_mapping_error():
- checking the returned dma_addr_t of dma_map_single and dma_map_page
by using dma_mapping_error():
dma_addr_t dma_handle;
dma_handle = pci_map_single(pdev, addr, size, direction);
if (pci_dma_mapping_error(pdev, dma_handle)) {
dma_handle = dma_map_single(dev, addr, size, direction);
if (dma_mapping_error(dev, dma_handle)) {
/*
* reduce current DMA mapping usage,
* delay and try again later or

122
Documentation/DMA-API.txt
View file

@ -4,20 +4,18 @@
James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
This document describes the DMA API. For a more gentle introduction
phrased in terms of the pci_ equivalents (and actual examples) see
Documentation/PCI/PCI-DMA-mapping.txt.
of the API (and actual examples) see
Documentation/DMA-API-HOWTO.txt.
This API is split into two pieces. Part I describes the API and the
corresponding pci_ API. Part II describes the extensions to the API
for supporting non-consistent memory machines. Unless you know that
your driver absolutely has to support non-consistent platforms (this
is usually only legacy platforms) you should only use the API
described in part I.
This API is split into two pieces. Part I describes the API. Part II
describes the extensions to the API for supporting non-consistent
memory machines. Unless you know that your driver absolutely has to
support non-consistent platforms (this is usually only legacy
platforms) you should only use the API described in part I.
Part I - pci_ and dma_ Equivalent API
Part I - dma_ API
-------------------------------------
To get the pci_ API, you must #include <linux/pci.h>
To get the dma_ API, you must #include <linux/dma-mapping.h>
@ -27,9 +25,6 @@ Part Ia - Using large dma-coherent buffers
void *
dma_alloc_coherent(struct device *dev, size_t size,
dma_addr_t *dma_handle, gfp_t flag)
void *
pci_alloc_consistent(struct pci_dev *dev, size_t size,
dma_addr_t *dma_handle)
Consistent memory is memory for which a write by either the device or
the processor can immediately be read by the processor or device
@ -53,15 +48,11 @@ The simplest way to do that is to use the dma_pool calls (see below).
The flag parameter (dma_alloc_coherent only) allows the caller to
specify the GFP_ flags (see kmalloc) for the allocation (the
implementation may choose to ignore flags that affect the location of
the returned memory, like GFP_DMA). For pci_alloc_consistent, you
must assume GFP_ATOMIC behaviour.
the returned memory, like GFP_DMA).
void
dma_free_coherent(struct device *dev, size_t size, void *cpu_addr,
dma_addr_t dma_handle)
void
pci_free_consistent(struct pci_dev *dev, size_t size, void *cpu_addr,
dma_addr_t dma_handle)
Free the region of consistent memory you previously allocated. dev,
size and dma_handle must all be the same as those passed into the
@ -89,10 +80,6 @@ for alignment, like queue heads needing to be aligned on N-byte boundaries.
dma_pool_create(const char *name, struct device *dev,
size_t size, size_t align, size_t alloc);
struct pci_pool *
pci_pool_create(const char *name, struct pci_device *dev,
size_t size, size_t align, size_t alloc);
The pool create() routines initialize a pool of dma-coherent buffers
for use with a given device. It must be called in a context which
can sleep.
@ -108,9 +95,6 @@ from this pool must not cross 4KByte boundaries.
void *dma_pool_alloc(struct dma_pool *pool, gfp_t gfp_flags,
dma_addr_t *dma_handle);
void *pci_pool_alloc(struct pci_pool *pool, gfp_t gfp_flags,
dma_addr_t *dma_handle);
This allocates memory from the pool; the returned memory will meet the size
and alignment requirements specified at creation time. Pass GFP_ATOMIC to
prevent blocking, or if it's permitted (not in_interrupt, not holding SMP locks),
@ -122,9 +106,6 @@ pool's device.
void dma_pool_free(struct dma_pool *pool, void *vaddr,
dma_addr_t addr);
void pci_pool_free(struct pci_pool *pool, void *vaddr,
dma_addr_t addr);
This puts memory back into the pool. The pool is what was passed to
the pool allocation routine; the cpu (vaddr) and dma addresses are what
were returned when that routine allocated the memory being freed.
@ -132,8 +113,6 @@ were returned when that routine allocated the memory being freed.
void dma_pool_destroy(struct dma_pool *pool);
void pci_pool_destroy(struct pci_pool *pool);
The pool destroy() routines free the resources of the pool. They must be
called in a context which can sleep. Make sure you've freed all allocated
memory back to the pool before you destroy it.
@ -144,8 +123,6 @@ Part Ic - DMA addressing limitations
int
dma_supported(struct device *dev, u64 mask)
int
pci_dma_supported(struct pci_dev *hwdev, u64 mask)
Checks to see if the device can support DMA to the memory described by
mask.
@ -159,8 +136,14 @@ driver writers.
int
dma_set_mask(struct device *dev, u64 mask)
Checks to see if the mask is possible and updates the device
parameters if it is.
Returns: 0 if successful and a negative error if not.
int
pci_set_dma_mask(struct pci_device *dev, u64 mask)
dma_set_coherent_mask(struct device *dev, u64 mask)
Checks to see if the mask is possible and updates the device
parameters if it is.
@ -187,9 +170,6 @@ Part Id - Streaming DMA mappings
dma_addr_t
dma_map_single(struct device *dev, void *cpu_addr, size_t size,
enum dma_data_direction direction)
dma_addr_t
pci_map_single(struct pci_dev *hwdev, void *cpu_addr, size_t size,
int direction)
Maps a piece of processor virtual memory so it can be accessed by the
device and returns the physical handle of the memory.
@ -198,14 +178,10 @@ The direction for both api's may be converted freely by casting.
However the dma_ API uses a strongly typed enumerator for its
direction:
DMA_NONE = PCI_DMA_NONE no direction (used for
debugging)
DMA_TO_DEVICE = PCI_DMA_TODEVICE data is going from the
memory to the device
DMA_FROM_DEVICE = PCI_DMA_FROMDEVICE data is coming from
the device to the
memory
DMA_BIDIRECTIONAL = PCI_DMA_BIDIRECTIONAL direction isn't known
DMA_NONE no direction (used for debugging)
DMA_TO_DEVICE data is going from the memory to the device
DMA_FROM_DEVICE data is coming from the device to the memory
DMA_BIDIRECTIONAL direction isn't known
Notes: Not all memory regions in a machine can be mapped by this
API. Further, regions that appear to be physically contiguous in
@ -268,9 +244,6 @@ cache lines are updated with data that the device may have changed).
void
dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
enum dma_data_direction direction)
void
pci_unmap_single(struct pci_dev *hwdev, dma_addr_t dma_addr,
size_t size, int direction)
Unmaps the region previously mapped. All the parameters passed in
must be identical to those passed in (and returned) by the mapping
@ -280,15 +253,9 @@ dma_addr_t
dma_map_page(struct device *dev, struct page *page,
unsigned long offset, size_t size,
enum dma_data_direction direction)
dma_addr_t
pci_map_page(struct pci_dev *hwdev, struct page *page,
unsigned long offset, size_t size, int direction)
void
dma_unmap_page(struct device *dev, dma_addr_t dma_address, size_t size,
enum dma_data_direction direction)
void
pci_unmap_page(struct pci_dev *hwdev, dma_addr_t dma_address,
size_t size, int direction)
API for mapping and unmapping for pages. All the notes and warnings
for the other mapping APIs apply here. Also, although the <offset>
@ -299,9 +266,6 @@ cache width is.
int
dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
int
pci_dma_mapping_error(struct pci_dev *hwdev, dma_addr_t dma_addr)
In some circumstances dma_map_single and dma_map_page will fail to create
a mapping. A driver can check for these errors by testing the returned
dma address with dma_mapping_error(). A non-zero return value means the mapping
@ -311,9 +275,6 @@ reduce current DMA mapping usage or delay and try again later).
int
dma_map_sg(struct device *dev, struct scatterlist *sg,
int nents, enum dma_data_direction direction)
int
pci_map_sg(struct pci_dev *hwdev, struct scatterlist *sg,
int nents, int direction)
Returns: the number of physical segments mapped (this may be shorter
than <nents> passed in if some elements of the scatter/gather list are
@ -353,9 +314,6 @@ accessed sg->address and sg->length as shown above.
void
dma_unmap_sg(struct device *dev, struct scatterlist *sg,
int nhwentries, enum dma_data_direction direction)
void
pci_unmap_sg(struct pci_dev *hwdev, struct scatterlist *sg,
int nents, int direction)
Unmap the previously mapped scatter/gather list. All the parameters
must be the same as those and passed in to the scatter/gather mapping
@ -365,21 +323,23 @@ Note: <nents> must be the number you passed in, *not* the number of
physical entries returned.
void
dma_sync_single(struct device *dev, dma_addr_t dma_handle, size_t size,
enum dma_data_direction direction)
dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle, size_t size,
enum dma_data_direction direction)
void
pci_dma_sync_single(struct pci_dev *hwdev, dma_addr_t dma_handle,
size_t size, int direction)
dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle, size_t size,
enum dma_data_direction direction)
void
dma_sync_sg(struct device *dev, struct scatterlist *sg, int nelems,
enum dma_data_direction direction)
dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nelems,
enum dma_data_direction direction)
void
pci_dma_sync_sg(struct pci_dev *hwdev, struct scatterlist *sg,
int nelems, int direction)
dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nelems,
enum dma_data_direction direction)
Synchronise a single contiguous or scatter/gather mapping. All the
parameters must be the same as those passed into the single mapping
API.
Synchronise a single contiguous or scatter/gather mapping for the cpu
and device. With the sync_sg API, all the parameters must be the same
as those passed into the single mapping API. With the sync_single API,
you can use dma_handle and size parameters that aren't identical to
those passed into the single mapping API to do a partial sync.
Notes: You must do this:
@ -461,9 +421,9 @@ void whizco_dma_map_sg_attrs(struct device *dev, dma_addr_t dma_addr,
Part II - Advanced dma_ usage
-----------------------------
Warning: These pieces of the DMA API have no PCI equivalent. They
should also not be used in the majority of cases, since they cater for
unlikely corner cases that don't belong in usual drivers.
Warning: These pieces of the DMA API should not be used in the
majority of cases, since they cater for unlikely corner cases that
don't belong in usual drivers.
If you don't understand how cache line coherency works between a
processor and an I/O device, you should not be using this part of the
@ -513,16 +473,6 @@ line, but it will guarantee that one or more cache lines fit exactly
into the width returned by this call. It will also always be a power
of two for easy alignment.
void
dma_sync_single_range(struct device *dev, dma_addr_t dma_handle,
unsigned long offset, size_t size,
enum dma_data_direction direction)
Does a partial sync, starting at offset and continuing for size. You
must be careful to observe the cache alignment and width when doing
anything like this. You must also be extra careful about accessing
memory you intend to sync partially.
void
dma_cache_sync(struct device *dev, void *vaddr, size_t size,
enum dma_data_direction direction)

2
Documentation/DocBook/device-drivers.tmpl
View file

@ -45,7 +45,7 @@
</sect1>
<sect1><title>Atomic and pointer manipulation</title>
!Iarch/x86/include/asm/atomic_32.h
!Iarch/x86/include/asm/atomic.h
!Iarch/x86/include/asm/unaligned.h
</sect1>

2
Documentation/DocBook/deviceiobook.tmpl
View file

@ -316,7 +316,7 @@ CPU B: spin_unlock_irqrestore(&amp;dev_lock, flags)
<chapter id="pubfunctions">
<title>Public Functions Provided</title>
!Iarch/x86/include/asm/io_32.h
!Iarch/x86/include/asm/io.h
!Elib/iomap.c
</chapter>

3
Documentation/DocBook/mac80211.tmpl
View file

@ -144,7 +144,7 @@ usage should require reading the full document.
this though and the recommendation to allow only a single
interface in STA mode at first!
</para>
!Finclude/net/mac80211.h ieee80211_if_init_conf
!Finclude/net/mac80211.h ieee80211_vif
</chapter>
<chapter id="rx-tx">
@ -234,7 +234,6 @@ usage should require reading the full document.
<title>Multiple queues and QoS support</title>
<para>TBD</para>
!Finclude/net/mac80211.h ieee80211_tx_queue_params
!Finclude/net/mac80211.h ieee80211_tx_queue_stats
</chapter>
<chapter id="AP">

18
Documentation/DocBook/mtdnand.tmpl
View file

@ -174,7 +174,7 @@
</para>
<programlisting>
static struct mtd_info *board_mtd;
static unsigned long baseaddr;
static void __iomem *baseaddr;
</programlisting>
<para>
Static example
@ -182,7 +182,7 @@ static unsigned long baseaddr;
<programlisting>
static struct mtd_info board_mtd;
static struct nand_chip board_chip;
static unsigned long baseaddr;
static void __iomem *baseaddr;
</programlisting>
</sect1>
<sect1 id="Partition_defines">
@ -283,8 +283,8 @@ int __init board_init (void)
}
/* map physical address */
baseaddr = (unsigned long)ioremap(CHIP_PHYSICAL_ADDRESS, 1024);
if(!baseaddr){
baseaddr = ioremap(CHIP_PHYSICAL_ADDRESS, 1024);
if (!baseaddr) {
printk("Ioremap to access NAND chip failed\n");
err = -EIO;
goto out_mtd;
@ -316,7 +316,7 @@ int __init board_init (void)
goto out;
out_ior:
iounmap((void *)baseaddr);
iounmap(baseaddr);
out_mtd:
kfree (board_mtd);
out:
@ -341,7 +341,7 @@ static void __exit board_cleanup (void)
nand_release (board_mtd);
/* unmap physical address */
iounmap((void *)baseaddr);
iounmap(baseaddr);
/* Free the MTD device structure */
kfree (board_mtd);
@ -488,7 +488,7 @@ static void board_select_chip (struct mtd_info *mtd, int chip)
The ECC bytes must be placed immidiately after the data
bytes in order to make the syndrome generator work. This
is contrary to the usual layout used by software ECC. The
seperation of data and out of band area is not longer
separation of data and out of band area is not longer
possible. The nand driver code handles this layout and
the remaining free bytes in the oob area are managed by
the autoplacement code. Provide a matching oob-layout
@ -560,7 +560,7 @@ static void board_select_chip (struct mtd_info *mtd, int chip)
bad blocks. They have factory marked good blocks. The marker pattern
is erased when the block is erased to be reused. So in case of
powerloss before writing the pattern back to the chip this block
would be lost and added to the bad blocks. Therefor we scan the
would be lost and added to the bad blocks. Therefore we scan the
chip(s) when we detect them the first time for good blocks and
store this information in a bad block table before erasing any
of the blocks.
@ -1094,7 +1094,7 @@ in this page</entry>
manufacturers specifications. This applies similar to the spare area.
</para>
<para>
Therefor NAND aware filesystems must either write in page size chunks
Therefore NAND aware filesystems must either write in page size chunks
or hold a writebuffer to collect smaller writes until they sum up to
pagesize. Available NAND aware filesystems: JFFS2, YAFFS.
</para>

2
Documentation/DocBook/v4l/common.xml
View file

@ -1170,7 +1170,7 @@ frames per second. If less than this number of frames is to be
captured or output, applications can request frame skipping or
duplicating on the driver side. This is especially useful when using
the &func-read; or &func-write;, which are not augmented by timestamps
or sequence counters, and to avoid unneccessary data copying.</para>
or sequence counters, and to avoid unnecessary data copying.</para>
<para>Finally these ioctls can be used to determine the number of
buffers used internally by a driver in read/write mode. For

3
Documentation/DocBook/v4l/io.xml
View file

@ -589,7 +589,8 @@ number of a video input as in &v4l2-input; field
<entry></entry>
<entry>A place holder for future extensions and custom
(driver defined) buffer types
<constant>V4L2_BUF_TYPE_PRIVATE</constant> and higher.</entry>
<constant>V4L2_BUF_TYPE_PRIVATE</constant> and higher. Applications
should set this to 0.</entry>
</row>
</tbody>
</tgroup>

2
Documentation/DocBook/v4l/vidioc-g-parm.xml
View file

@ -55,7 +55,7 @@ captured or output, applications can request frame skipping or
duplicating on the driver side. This is especially useful when using
the <function>read()</function> or <function>write()</function>, which
are not augmented by timestamps or sequence counters, and to avoid
unneccessary data copying.</para>
unnecessary data copying.</para>
<para>Further these ioctls can be used to determine the number of
buffers used internally by a driver in read/write mode. For

40
Documentation/DocBook/v4l/vidioc-qbuf.xml
View file

@ -54,12 +54,10 @@ to enqueue an empty (capturing) or filled (output) buffer in the
driver's incoming queue. The semantics depend on the selected I/O
method.</para>
<para>To enqueue a <link linkend="mmap">memory mapped</link>
buffer applications set the <structfield>type</structfield> field of a
&v4l2-buffer; to the same buffer type as previously &v4l2-format;
<structfield>type</structfield> and &v4l2-requestbuffers;
<structfield>type</structfield>, the <structfield>memory</structfield>
field to <constant>V4L2_MEMORY_MMAP</constant> and the
<para>To enqueue a buffer applications set the <structfield>type</structfield>
field of a &v4l2-buffer; to the same buffer type as was previously used
with &v4l2-format; <structfield>type</structfield> and &v4l2-requestbuffers;
<structfield>type</structfield>. Applications must also set the
<structfield>index</structfield> field. Valid index numbers range from
zero to the number of buffers allocated with &VIDIOC-REQBUFS;
(&v4l2-requestbuffers; <structfield>count</structfield>) minus one. The
@ -70,8 +68,19 @@ intended for output (<structfield>type</structfield> is
<constant>V4L2_BUF_TYPE_VBI_OUTPUT</constant>) applications must also
initialize the <structfield>bytesused</structfield>,
<structfield>field</structfield> and
<structfield>timestamp</structfield> fields. See <xref
linkend="buffer" /> for details. When
<structfield>timestamp</structfield> fields, see <xref
linkend="buffer" /> for details.
Applications must also set <structfield>flags</structfield> to 0. If a driver
supports capturing from specific video inputs and you want to specify a video
input, then <structfield>flags</structfield> should be set to
<constant>V4L2_BUF_FLAG_INPUT</constant> and the field
<structfield>input</structfield> must be initialized to the desired input.
The <structfield>reserved</structfield> field must be set to 0.
</para>
<para>To enqueue a <link linkend="mmap">memory mapped</link>
buffer applications set the <structfield>memory</structfield>
field to <constant>V4L2_MEMORY_MMAP</constant>. When
<constant>VIDIOC_QBUF</constant> is called with a pointer to this
structure the driver sets the
<constant>V4L2_BUF_FLAG_MAPPED</constant> and
@ -81,14 +90,10 @@ structure the driver sets the
&EINVAL;.</para>
<para>To enqueue a <link linkend="userp">user pointer</link>
buffer applications set the <structfield>type</structfield> field of a
&v4l2-buffer; to the same buffer type as previously &v4l2-format;
<structfield>type</structfield> and &v4l2-requestbuffers;
<structfield>type</structfield>, the <structfield>memory</structfield>
field to <constant>V4L2_MEMORY_USERPTR</constant> and the
buffer applications set the <structfield>memory</structfield>
field to <constant>V4L2_MEMORY_USERPTR</constant>, the
<structfield>m.userptr</structfield> field to the address of the
buffer and <structfield>length</structfield> to its size. When the
buffer is intended for output additional fields must be set as above.
buffer and <structfield>length</structfield> to its size.
When <constant>VIDIOC_QBUF</constant> is called with a pointer to this
structure the driver sets the <constant>V4L2_BUF_FLAG_QUEUED</constant>
flag and clears the <constant>V4L2_BUF_FLAG_MAPPED</constant> and
@ -96,13 +101,14 @@ flag and clears the <constant>V4L2_BUF_FLAG_MAPPED</constant> and
<structfield>flags</structfield> field, or it returns an error code.
This ioctl locks the memory pages of the buffer in physical memory,
they cannot be swapped out to disk. Buffers remain locked until
dequeued, until the &VIDIOC-STREAMOFF; or &VIDIOC-REQBUFS; ioctl are
dequeued, until the &VIDIOC-STREAMOFF; or &VIDIOC-REQBUFS; ioctl is
called, or until the device is closed.</para>
<para>Applications call the <constant>VIDIOC_DQBUF</constant>
ioctl to dequeue a filled (capturing) or displayed (output) buffer
from the driver's outgoing queue. They just set the
<structfield>type</structfield> and <structfield>memory</structfield>
<structfield>type</structfield>, <structfield>memory</structfield>
and <structfield>reserved</structfield>
fields of a &v4l2-buffer; as above, when <constant>VIDIOC_DQBUF</constant>
is called with a pointer to this structure the driver fills the
remaining fields or returns an error code.</para>

7
Documentation/DocBook/v4l/vidioc-querybuf.xml
View file

@ -54,12 +54,13 @@ buffer at any time after buffers have been allocated with the
&VIDIOC-REQBUFS; ioctl.</para>
<para>Applications set the <structfield>type</structfield> field
of a &v4l2-buffer; to the same buffer type as previously
of a &v4l2-buffer; to the same buffer type as was previously used with
&v4l2-format; <structfield>type</structfield> and &v4l2-requestbuffers;
<structfield>type</structfield>, and the <structfield>index</structfield>
field. Valid index numbers range from zero
to the number of buffers allocated with &VIDIOC-REQBUFS;
(&v4l2-requestbuffers; <structfield>count</structfield>) minus one.
The <structfield>reserved</structfield> field should to set to 0.
After calling <constant>VIDIOC_QUERYBUF</constant> with a pointer to
this structure drivers return an error code or fill the rest of
the structure.</para>
@ -68,8 +69,8 @@ the structure.</para>
<constant>V4L2_BUF_FLAG_MAPPED</constant>,
<constant>V4L2_BUF_FLAG_QUEUED</constant> and
<constant>V4L2_BUF_FLAG_DONE</constant> flags will be valid. The
<structfield>memory</structfield> field will be set to
<constant>V4L2_MEMORY_MMAP</constant>, the <structfield>m.offset</structfield>
<structfield>memory</structfield> field will be set to the current
I/O method, the <structfield>m.offset</structfield>
contains the offset of the buffer from the start of the device memory,
the <structfield>length</structfield> field its size. The driver may
or may not set the remaining fields and flags, they are meaningless in

36
Documentation/DocBook/v4l/vidioc-reqbufs.xml
View file

@ -54,23 +54,23 @@ I/O. Memory mapped buffers are located in device memory and must be
allocated with this ioctl before they can be mapped into the
application's address space. User buffers are allocated by
applications themselves, and this ioctl is merely used to switch the
driver into user pointer I/O mode.</para>
driver into user pointer I/O mode and to setup some internal structures.</para>
<para>To allocate device buffers applications initialize three
fields of a <structname>v4l2_requestbuffers</structname> structure.
<para>To allocate device buffers applications initialize all
fields of the <structname>v4l2_requestbuffers</structname> structure.
They set the <structfield>type</structfield> field to the respective
stream or buffer type, the <structfield>count</structfield> field to
the desired number of buffers, and <structfield>memory</structfield>
must be set to <constant>V4L2_MEMORY_MMAP</constant>. When the ioctl
is called with a pointer to this structure the driver attempts to
allocate the requested number of buffers and stores the actual number
the desired number of buffers, <structfield>memory</structfield>
must be set to the requested I/O method and the reserved array
must be zeroed. When the ioctl
is called with a pointer to this structure the driver will attempt to allocate
the requested number of buffers and it stores the actual number
allocated in the <structfield>count</structfield> field. It can be
smaller than the number requested, even zero, when the driver runs out
of free memory. A larger number is possible when the driver requires
more buffers to function correctly.<footnote>
<para>For example video output requires at least two buffers,
of free memory. A larger number is also possible when the driver requires
more buffers to function correctly. For example video output requires at least two buffers,
one displayed and one filled by the application.</para>
</footnote> When memory mapping I/O is not supported the ioctl
<para>When the I/O method is not supported the ioctl
returns an &EINVAL;.</para>
<para>Applications can call <constant>VIDIOC_REQBUFS</constant>
@ -81,14 +81,6 @@ in progress, an implicit &VIDIOC-STREAMOFF;. <!-- mhs: I see no
reason why munmap()ping one or even all buffers must imply
streamoff.--></para>
<para>To negotiate user pointer I/O, applications initialize only
the <structfield>type</structfield> field and set
<structfield>memory</structfield> to
<constant>V4L2_MEMORY_USERPTR</constant>. When the ioctl is called
with a pointer to this structure the driver prepares for user pointer
I/O, when this I/O method is not supported the ioctl returns an
&EINVAL;.</para>
<table pgwide="1" frame="none" id="v4l2-requestbuffers">
<title>struct <structname>v4l2_requestbuffers</structname></title>
<tgroup cols="3">
@ -97,9 +89,7 @@ I/O, when this I/O method is not supported the ioctl returns an
<row>
<entry>__u32</entry>
<entry><structfield>count</structfield></entry>
<entry>The number of buffers requested or granted. This
field is only used when <structfield>memory</structfield> is set to
<constant>V4L2_MEMORY_MMAP</constant>.</entry>
<entry>The number of buffers requested or granted.</entry>
</row>
<row>
<entry>&v4l2-buf-type;</entry>
@ -120,7 +110,7 @@ as the &v4l2-format; <structfield>type</structfield> field. See <xref
<entry><structfield>reserved</structfield>[2]</entry>
<entry>A place holder for future extensions and custom
(driver defined) buffer types <constant>V4L2_BUF_TYPE_PRIVATE</constant> and
higher.</entry>
higher. This array should be zeroed by applications.</entry>
</row>
</tbody>
</tgroup>

105
Documentation/HOWTO
View file

@ -221,8 +221,8 @@ branches. These different branches are:
- main 2.6.x kernel tree
- 2.6.x.y -stable kernel tree
- 2.6.x -git kernel patches
- 2.6.x -mm kernel patches
- subsystem specific kernel trees and patches
- the 2.6.x -next kernel tree for integration tests
2.6.x kernel tree
-----------------
@ -232,7 +232,7 @@ process is as follows:
- As soon as a new kernel is released a two weeks window is open,
during this period of time maintainers can submit big diffs to
Linus, usually the patches that have already been included in the
-mm kernel for a few weeks. The preferred way to submit big changes
-next kernel for a few weeks. The preferred way to submit big changes
is using git (the kernel's source management tool, more information
can be found at http://git.or.cz/) but plain patches are also just
fine.
@ -293,84 +293,43 @@ daily and represent the current state of Linus' tree. They are more
experimental than -rc kernels since they are generated automatically
without even a cursory glance to see if they are sane.
2.6.x -mm kernel patches
------------------------
These are experimental kernel patches released by Andrew Morton. Andrew
takes all of the different subsystem kernel trees and patches and mushes
them together, along with a lot of patches that have been plucked from
the linux-kernel mailing list. This tree serves as a proving ground for
new features and patches. Once a patch has proved its worth in -mm for
a while Andrew or the subsystem maintainer pushes it on to Linus for
inclusion in mainline.
It is heavily encouraged that all new patches get tested in the -mm tree
before they are sent to Linus for inclusion in the main kernel tree. Code
which does not make an appearance in -mm before the opening of the merge
window will prove hard to merge into the mainline.
These kernels are not appropriate for use on systems that are supposed
to be stable and they are more risky to run than any of the other
branches.
If you wish to help out with the kernel development process, please test
and use these kernel releases and provide feedback to the linux-kernel
mailing list if you have any problems, and if everything works properly.
In addition to all the other experimental patches, these kernels usually
also contain any changes in the mainline -git kernels available at the
time of release.
The -mm kernels are not released on a fixed schedule, but usually a few
-mm kernels are released in between each -rc kernel (1 to 3 is common).
Subsystem Specific kernel trees and patches
-------------------------------------------
A number of the different kernel subsystem developers expose their
development trees so that others can see what is happening in the
different areas of the kernel. These trees are pulled into the -mm
kernel releases as described above.
The maintainers of the various kernel subsystems --- and also many
kernel subsystem developers --- expose their current state of
development in source repositories. That way, others can see what is
happening in the different areas of the kernel. In areas where
development is rapid, a developer may be asked to base his submissions
onto such a subsystem kernel tree so that conflicts between the
submission and other already ongoing work are avoided.
Here is a list of some of the different kernel trees available:
git trees:
- Kbuild development tree, Sam Ravnborg <sam@ravnborg.org>
git.kernel.org:/pub/scm/linux/kernel/git/sam/kbuild.git
Most of these repositories are git trees, but there are also other SCMs
in use, or patch queues being published as quilt series. Addresses of
these subsystem repositories are listed in the MAINTAINERS file. Many
of them can be browsed at http://git.kernel.org/.
- ACPI development tree, Len Brown <len.brown@intel.com>
git.kernel.org:/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6.git
Before a proposed patch is committed to such a subsystem tree, it is
subject to review which primarily happens on mailing lists (see the
respective section below). For several kernel subsystems, this review
process is tracked with the tool patchwork. Patchwork offers a web
interface which shows patch postings, any comments on a patch or
revisions to it, and maintainers can mark patches as under review,
accepted, or rejected. Most of these patchwork sites are listed at
http://patchwork.kernel.org/ or http://patchwork.ozlabs.org/.
- Block development tree, Jens Axboe <jens.axboe@oracle.com>
git.kernel.org:/pub/scm/linux/kernel/git/axboe/linux-2.6-block.git
2.6.x -next kernel tree for integration tests
---------------------------------------------
Before updates from subsystem trees are merged into the mainline 2.6.x
tree, they need to be integration-tested. For this purpose, a special
testing repository exists into which virtually all subsystem trees are
pulled on an almost daily basis:
http://git.kernel.org/?p=linux/kernel/git/sfr/linux-next.git
http://linux.f-seidel.de/linux-next/pmwiki/
- DRM development tree, Dave Airlie <airlied@linux.ie>
git.kernel.org:/pub/scm/linux/kernel/git/airlied/drm-2.6.git
This way, the -next kernel gives a summary outlook onto what will be
expected to go into the mainline kernel at the next merge period.
Adventurous testers are very welcome to runtime-test the -next kernel.
- ia64 development tree, Tony Luck <tony.luck@intel.com>
git.kernel.org:/pub/scm/linux/kernel/git/aegl/linux-2.6.git
- infiniband, Roland Dreier <rolandd@cisco.com>
git.kernel.org:/pub/scm/linux/kernel/git/roland/infiniband.git
- libata, Jeff Garzik <jgarzik@pobox.com>
git.kernel.org:/pub/scm/linux/kernel/git/jgarzik/libata-dev.git
- network drivers, Jeff Garzik <jgarzik@pobox.com>
git.kernel.org:/pub/scm/linux/kernel/git/jgarzik/netdev-2.6.git
- pcmcia, Dominik Brodowski <linux@dominikbrodowski.net>
git.kernel.org:/pub/scm/linux/kernel/git/brodo/pcmcia-2.6.git
- SCSI, James Bottomley <James.Bottomley@hansenpartnership.com>
git.kernel.org:/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6.git
- x86, Ingo Molnar <mingo@elte.hu>
git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-x86.git
quilt trees:
- USB, Driver Core, and I2C, Greg Kroah-Hartman <gregkh@suse.de>
kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/
Other kernel trees can be found listed at http://git.kernel.org/ and in
the MAINTAINERS file.
Bug Reporting
-------------

2
Documentation/IO-mapping.txt
View file

@ -157,7 +157,7 @@ For such memory, you can do things like
* access only the 640k-1MB area, so anything else
* has to be remapped.
*/
char * baseptr = ioremap(0xFC000000, 1024*1024);
void __iomem *baseptr = ioremap(0xFC000000, 1024*1024);
/* write a 'A' to the offset 10 of the area */
writeb('A',baseptr+10);

12
Documentation/IPMI.txt
View file

@ -365,6 +365,7 @@ You can change this at module load time (for a module) with:
regshifts=<shift1>,<shift2>,...
slave_addrs=<addr1>,<addr2>,...
force_kipmid=<enable1>,<enable2>,...
kipmid_max_busy_us=<ustime1>,<ustime2>,...
unload_when_empty=[0|1]
Each of these except si_trydefaults is a list, the first item for the
@ -433,6 +434,7 @@ kernel command line as:
ipmi_si.regshifts=<shift1>,<shift2>,...
ipmi_si.slave_addrs=<addr1>,<addr2>,...
ipmi_si.force_kipmid=<enable1>,<enable2>,...
ipmi_si.kipmid_max_busy_us=<ustime1>,<ustime2>,...
It works the same as the module parameters of the same names.
@ -450,6 +452,16 @@ force this thread on or off. If you force it off and don't have
interrupts, the driver will run VERY slowly. Don't blame me,
these interfaces suck.
Unfortunately, this thread can use a lot of CPU depending on the
interface's performance. This can waste a lot of CPU and cause
various issues with detecting idle CPU and using extra power. To
avoid this, the kipmid_max_busy_us sets the maximum amount of time, in
microseconds, that kipmid will spin before sleeping for a tick. This
value sets a balance between performance and CPU waste and needs to be
tuned to your needs. Maybe, someday, auto-tuning will be added, but
that's not a simple thing and even the auto-tuning would need to be
tuned to the user's desired performance.
The driver supports a hot add and remove of interfaces. This way,
interfaces can be added or removed after the kernel is up and running.
This is done using /sys/modules/ipmi_si/parameters/hotmod, which is a

4
Documentation/Makefile
View file

@ -1,3 +1,3 @@
obj-m := DocBook/ accounting/ auxdisplay/ connector/ \
filesystems/configfs/ ia64/ networking/ \
pcmcia/ spi/ video4linux/ vm/ watchdog/src/
filesystems/ filesystems/configfs/ ia64/ laptops/ networking/ \
pcmcia/ spi/ timers/ video4linux/ vm/ watchdog/src/

10
Documentation/RCU/00-INDEX
View file

@ -6,16 +6,22 @@ checklist.txt
- Review Checklist for RCU Patches
listRCU.txt
- Using RCU to Protect Read-Mostly Linked Lists
lockdep.txt
- RCU and lockdep checking
NMI-RCU.txt
- Using RCU to Protect Dynamic NMI Handlers
rcubarrier.txt
- RCU and Unloadable Modules
rculist_nulls.txt
- RCU list primitives for use with SLAB_DESTROY_BY_RCU
rcuref.txt
- Reference-count design for elements of lists/arrays protected by RCU
rcu.txt
- RCU Concepts
rcubarrier.txt
- Unloading modules that use RCU callbacks
RTFP.txt
- List of RCU papers (bibliography) going back to 1980.
stallwarn.txt
- RCU CPU stall warnings (CONFIG_RCU_CPU_STALL_DETECTOR)
torture.txt
- RCU Torture Test Operation (CONFIG_RCU_TORTURE_TEST)
trace.txt

61
Documentation/RCU/RTFP.txt
View file

@ -25,10 +25,10 @@ to be referencing the data structure. However, this mechanism was not
optimized for modern computer systems, which is not surprising given
that these overheads were not so expensive in the mid-80s. Nonetheless,
passive serialization appears to be the first deferred-destruction
mechanism to be used in production. Furthermore, the relevant patent has
lapsed, so this approach may be used in non-GPL software, if desired.
(In contrast, use of RCU is permitted only in software licensed under
GPL. Sorry!!!)
mechanism to be used in production. Furthermore, the relevant patent
has lapsed, so this approach may be used in non-GPL software, if desired.
(In contrast, implementation of RCU is permitted only in software licensed
under either GPL or LGPL. Sorry!!!)
In 1990, Pugh [Pugh90] noted that explicitly tracking which threads
were reading a given data structure permitted deferred free to operate
@ -150,6 +150,18 @@ preemptible RCU [PaulEMcKenney2007PreemptibleRCU], and the three-part
LWN "What is RCU?" series [PaulEMcKenney2007WhatIsRCUFundamentally,
PaulEMcKenney2008WhatIsRCUUsage, and PaulEMcKenney2008WhatIsRCUAPI].
2008 saw a journal paper on real-time RCU [DinakarGuniguntala2008IBMSysJ],
a history of how Linux changed RCU more than RCU changed Linux
[PaulEMcKenney2008RCUOSR], and a design overview of hierarchical RCU
[PaulEMcKenney2008HierarchicalRCU].
2009 introduced user-level RCU algorithms [PaulEMcKenney2009MaliciousURCU],
which Mathieu Desnoyers is now maintaining [MathieuDesnoyers2009URCU]
[MathieuDesnoyersPhD]. TINY_RCU [PaulEMcKenney2009BloatWatchRCU] made
its appearance, as did expedited RCU [PaulEMcKenney2009expeditedRCU].
The problem of resizeable RCU-protected hash tables may now be on a path
to a solution [JoshTriplett2009RPHash].
Bibtex Entries
@article{Kung80
@ -730,6 +742,11 @@ Revised:
"
}
#
# "What is RCU?" LWN series.
#
########################################################################
@article{DinakarGuniguntala2008IBMSysJ
,author="D. Guniguntala and P. E. McKenney and J. Triplett and J. Walpole"
,title="The read-copy-update mechanism for supporting real-time applications on shared-memory multiprocessor systems with {Linux}"
@ -820,3 +837,39 @@ Revised:
Uniprocessor assumptions allow simplified RCU implementation.
"
}
@unpublished{PaulEMcKenney2009expeditedRCU
,Author="Paul E. McKenney"
,Title="[{PATCH} -tip 0/3] expedited 'big hammer' {RCU} grace periods"
,month="June"
,day="25"
,year="2009"
,note="Available:
\url{http://lkml.org/lkml/2009/6/25/306}
[Viewed August 16, 2009]"
,annotation="
First posting of expedited RCU to be accepted into -tip.
"
}
@unpublished{JoshTriplett2009RPHash
,Author="Josh Triplett"
,Title="Scalable concurrent hash tables via relativistic programming"
,month="September"
,year="2009"
,note="Linux Plumbers Conference presentation"
,annotation="
RP fun with hash tables.
"
}
@phdthesis{MathieuDesnoyersPhD
, title = "Low-Impact Operating System Tracing"
, author = "Mathieu Desnoyers"
, school = "Ecole Polytechnique de Montr\'{e}al"
, month = "December"
, year = 2009
,note="Available:
\url{http://www.lttng.org/pub/thesis/desnoyers-dissertation-2009-12.pdf}
[Viewed December 9, 2009]"
}

204
Documentation/RCU/checklist.txt
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@ -8,13 +8,12 @@ would cause. This list is based on experiences reviewing such patches
over a rather long period of time, but improvements are always welcome!
0. Is RCU being applied to a read-mostly situation? If the data
structure is updated more than about 10% of the time, then
you should strongly consider some other approach, unless
detailed performance measurements show that RCU is nonetheless
the right tool for the job. Yes, you might think of RCU
as simply cutting overhead off of the readers and imposing it
on the writers. That is exactly why normal uses of RCU will
do much more reading than updating.
structure is updated more than about 10% of the time, then you
should strongly consider some other approach, unless detailed
performance measurements show that RCU is nonetheless the right
tool for the job. Yes, RCU does reduce read-side overhead by
increasing write-side overhead, which is exactly why normal uses
of RCU will do much more reading than updating.
Another exception is where performance is not an issue, and RCU
provides a simpler implementation. An example of this situation
@ -35,13 +34,13 @@ over a rather long period of time, but improvements are always welcome!
If you choose #b, be prepared to describe how you have handled
memory barriers on weakly ordered machines (pretty much all of
them -- even x86 allows reads to be reordered), and be prepared
to explain why this added complexity is worthwhile. If you
choose #c, be prepared to explain how this single task does not
become a major bottleneck on big multiprocessor machines (for
example, if the task is updating information relating to itself
that other tasks can read, there by definition can be no
bottleneck).
them -- even x86 allows later loads to be reordered to precede
earlier stores), and be prepared to explain why this added
complexity is worthwhile. If you choose #c, be prepared to
explain how this single task does not become a major bottleneck on
big multiprocessor machines (for example, if the task is updating
information relating to itself that other tasks can read, there
by definition can be no bottleneck).
2. Do the RCU read-side critical sections make proper use of
rcu_read_lock() and friends? These primitives are needed
@ -51,8 +50,10 @@ over a rather long period of time, but improvements are always welcome!
actuarial risk of your kernel.
As a rough rule of thumb, any dereference of an RCU-protected
pointer must be covered by rcu_read_lock() or rcu_read_lock_bh()
or by the appropriate update-side lock.
pointer must be covered by rcu_read_lock(), rcu_read_lock_bh(),
rcu_read_lock_sched(), or by the appropriate update-side lock.
Disabling of preemption can serve as rcu_read_lock_sched(), but
is less readable.
3. Does the update code tolerate concurrent accesses?
@ -62,25 +63,27 @@ over a rather long period of time, but improvements are always welcome!
of ways to handle this concurrency, depending on the situation:
a. Use the RCU variants of the list and hlist update
primitives to add, remove, and replace elements on an
RCU-protected list. Alternatively, use the RCU-protected
trees that have been added to the Linux kernel.
primitives to add, remove, and replace elements on
an RCU-protected list. Alternatively, use the other
RCU-protected data structures that have been added to
the Linux kernel.
This is almost always the best approach.
b. Proceed as in (a) above, but also maintain per-element
locks (that are acquired by both readers and writers)
that guard per-element state. Of course, fields that
the readers refrain from accessing can be guarded by the
update-side lock.
the readers refrain from accessing can be guarded by
some other lock acquired only by updaters, if desired.
This works quite well, also.
c. Make updates appear atomic to readers. For example,
pointer updates to properly aligned fields will appear
atomic, as will individual atomic primitives. Operations
performed under a lock and sequences of multiple atomic
primitives will -not- appear to be atomic.
pointer updates to properly aligned fields will
appear atomic, as will individual atomic primitives.
Sequences of perations performed under a lock will -not-
appear to be atomic to RCU readers, nor will sequences
of multiple atomic primitives.
This can work, but is starting to get a bit tricky.
@ -98,9 +101,9 @@ over a rather long period of time, but improvements are always welcome!
a new structure containing updated values.
4. Weakly ordered CPUs pose special challenges. Almost all CPUs
are weakly ordered -- even i386 CPUs allow reads to be reordered.
RCU code must take all of the following measures to prevent
memory-corruption problems:
are weakly ordered -- even x86 CPUs allow later loads to be
reordered to precede earlier stores. RCU code must take all of
the following measures to prevent memory-corruption problems:
a. Readers must maintain proper ordering of their memory
accesses. The rcu_dereference() primitive ensures that
@ -113,14 +116,25 @@ over a rather long period of time, but improvements are always welcome!
The rcu_dereference() primitive is also an excellent
documentation aid, letting the person reading the code
know exactly which pointers are protected by RCU.
Please note that compilers can also reorder code, and
they are becoming increasingly aggressive about doing
just that. The rcu_dereference() primitive therefore
also prevents destructive compiler optimizations.
The rcu_dereference() primitive is used by the various
"_rcu()" list-traversal primitives, such as the
list_for_each_entry_rcu(). Note that it is perfectly
legal (if redundant) for update-side code to use
rcu_dereference() and the "_rcu()" list-traversal
primitives. This is particularly useful in code
that is common to readers and updaters.
The rcu_dereference() primitive is used by the
various "_rcu()" list-traversal primitives, such
as the list_for_each_entry_rcu(). Note that it is
perfectly legal (if redundant) for update-side code to
use rcu_dereference() and the "_rcu()" list-traversal
primitives. This is particularly useful in code that
is common to readers and updaters. However, lockdep
will complain if you access rcu_dereference() outside
of an RCU read-side critical section. See lockdep.txt
to learn what to do about this.
Of course, neither rcu_dereference() nor the "_rcu()"
list-traversal primitives can substitute for a good
concurrency design coordinating among multiple updaters.
b. If the list macros are being used, the list_add_tail_rcu()
and list_add_rcu() primitives must be used in order
@ -135,11 +149,14 @@ over a rather long period of time, but improvements are always welcome!
readers. Similarly, if the hlist macros are being used,
the hlist_del_rcu() primitive is required.
The list_replace_rcu() primitive may be used to
replace an old structure with a new one in an
RCU-protected list.
The list_replace_rcu() and hlist_replace_rcu() primitives
may be used to replace an old structure with a new one
in their respective types of RCU-protected lists.
d. Updates must ensure that initialization of a given
d. Rules similar to (4b) and (4c) apply to the "hlist_nulls"
type of RCU-protected linked lists.
e. Updates must ensure that initialization of a given
structure happens before pointers to that structure are
publicized. Use the rcu_assign_pointer() primitive
when publicizing a pointer to a structure that can
@ -151,16 +168,31 @@ over a rather long period of time, but improvements are always welcome!
it cannot block.
6. Since synchronize_rcu() can block, it cannot be called from
any sort of irq context. Ditto for synchronize_sched() and
synchronize_srcu().
any sort of irq context. The same rule applies for
synchronize_rcu_bh(), synchronize_sched(), synchronize_srcu(),
synchronize_rcu_expedited(), synchronize_rcu_bh_expedited(),
synchronize_sched_expedite(), and synchronize_srcu_expedited().
7. If the updater uses call_rcu(), then the corresponding readers
must use rcu_read_lock() and rcu_read_unlock(). If the updater
uses call_rcu_bh(), then the corresponding readers must use
rcu_read_lock_bh() and rcu_read_unlock_bh(). If the updater
uses call_rcu_sched(), then the corresponding readers must
disable preemption. Mixing things up will result in confusion
and broken kernels.
The expedited forms of these primitives have the same semantics
as the non-expedited forms, but expediting is both expensive
and unfriendly to real-time workloads. Use of the expedited
primitives should be restricted to rare configuration-change
operations that would not normally be undertaken while a real-time
workload is running.
7. If the updater uses call_rcu() or synchronize_rcu(), then the
corresponding readers must use rcu_read_lock() and
rcu_read_unlock(). If the updater uses call_rcu_bh() or
synchronize_rcu_bh(), then the corresponding readers must
use rcu_read_lock_bh() and rcu_read_unlock_bh(). If the
updater uses call_rcu_sched() or synchronize_sched(), then
the corresponding readers must disable preemption, possibly
by calling rcu_read_lock_sched() and rcu_read_unlock_sched().
If the updater uses synchronize_srcu(), the the corresponding
readers must use srcu_read_lock() and srcu_read_unlock(),
and with the same srcu_struct. The rules for the expedited
primitives are the same as for their non-expedited counterparts.
Mixing things up will result in confusion and broken kernels.
One exception to this rule: rcu_read_lock() and rcu_read_unlock()
may be substituted for rcu_read_lock_bh() and rcu_read_unlock_bh()
@ -212,6 +244,8 @@ over a rather long period of time, but improvements are always welcome!
e. Periodically invoke synchronize_rcu(), permitting a limited
number of updates per grace period.
The same cautions apply to call_rcu_bh() and call_rcu_sched().
9. All RCU list-traversal primitives, which include
rcu_dereference(), list_for_each_entry_rcu(),
list_for_each_continue_rcu(), and list_for_each_safe_rcu(),
@ -219,7 +253,9 @@ over a rather long period of time, but improvements are always welcome!
must be protected by appropriate update-side locks. RCU
read-side critical sections are delimited by rcu_read_lock()
and rcu_read_unlock(), or by similar primitives such as
rcu_read_lock_bh() and rcu_read_unlock_bh().
rcu_read_lock_bh() and rcu_read_unlock_bh(), in which case
the matching rcu_dereference() primitive must be used in order
to keep lockdep happy, in this case, rcu_dereference_bh().
The reason that it is permissible to use RCU list-traversal
primitives when the update-side lock is held is that doing so
@ -229,7 +265,8 @@ over a rather long period of time, but improvements are always welcome!
10. Conversely, if you are in an RCU read-side critical section,
and you don't hold the appropriate update-side lock, you -must-
use the "_rcu()" variants of the list macros. Failing to do so
will break Alpha and confuse people reading your code.
will break Alpha, cause aggressive compilers to generate bad code,
and confuse people trying to read your code.
11. Note that synchronize_rcu() -only- guarantees to wait until
all currently executing rcu_read_lock()-protected RCU read-side
@ -239,15 +276,21 @@ over a rather long period of time, but improvements are always welcome!
rcu_read_lock()-protected read-side critical sections, do -not-
use synchronize_rcu().
If you want to wait for some of these other things, you might
instead need to use synchronize_irq() or synchronize_sched().
Similarly, disabling preemption is not an acceptable substitute
for rcu_read_lock(). Code that attempts to use preemption
disabling where it should be using rcu_read_lock() will break
in real-time kernel builds.
If you want to wait for interrupt handlers, NMI handlers, and
code under the influence of preempt_disable(), you instead
need to use synchronize_irq() or synchronize_sched().
12. Any lock acquired by an RCU callback must be acquired elsewhere
with softirq disabled, e.g., via spin_lock_irqsave(),
spin_lock_bh(), etc. Failing to disable irq on a given
acquisition of that lock will result in deadlock as soon as the
RCU callback happens to interrupt that acquisition's critical
section.
acquisition of that lock will result in deadlock as soon as
the RCU softirq handler happens to run your RCU callback while
interrupting that acquisition's critical section.
13. RCU callbacks can be and are executed in parallel. In many cases,
the callback code simply wrappers around kfree(), so that this
@ -265,29 +308,30 @@ over a rather long period of time, but improvements are always welcome!
not the case, a self-spawning RCU callback would prevent the
victim CPU from ever going offline.)
14. SRCU (srcu_read_lock(), srcu_read_unlock(), and synchronize_srcu())
may only be invoked from process context. Unlike other forms of
RCU, it -is- permissible to block in an SRCU read-side critical
section (demarked by srcu_read_lock() and srcu_read_unlock()),
hence the "SRCU": "sleepable RCU". Please note that if you
don't need to sleep in read-side critical sections, you should
be using RCU rather than SRCU, because RCU is almost always
faster and easier to use than is SRCU.
14. SRCU (srcu_read_lock(), srcu_read_unlock(), srcu_dereference(),
synchronize_srcu(), and synchronize_srcu_expedited()) may only
be invoked from process context. Unlike other forms of RCU, it
-is- permissible to block in an SRCU read-side critical section
(demarked by srcu_read_lock() and srcu_read_unlock()), hence the
"SRCU": "sleepable RCU". Please note that if you don't need
to sleep in read-side critical sections, you should be using
RCU rather than SRCU, because RCU is almost always faster and
easier to use than is SRCU.
Also unlike other forms of RCU, explicit initialization
and cleanup is required via init_srcu_struct() and
cleanup_srcu_struct(). These are passed a "struct srcu_struct"
that defines the scope of a given SRCU domain. Once initialized,
the srcu_struct is passed to srcu_read_lock(), srcu_read_unlock()
and synchronize_srcu(). A given synchronize_srcu() waits only
for SRCU read-side critical sections governed by srcu_read_lock()
and srcu_read_unlock() calls that have been passd the same
srcu_struct. This property is what makes sleeping read-side
critical sections tolerable -- a given subsystem delays only
its own updates, not those of other subsystems using SRCU.
Therefore, SRCU is less prone to OOM the system than RCU would
be if RCU's read-side critical sections were permitted to
sleep.
synchronize_srcu(), and synchronize_srcu_expedited(). A given
synchronize_srcu() waits only for SRCU read-side critical
sections governed by srcu_read_lock() and srcu_read_unlock()
calls that have been passed the same srcu_struct. This property
is what makes sleeping read-side critical sections tolerable --
a given subsystem delays only its own updates, not those of other
subsystems using SRCU. Therefore, SRCU is less prone to OOM the
system than RCU would be if RCU's read-side critical sections
were permitted to sleep.
The ability to sleep in read-side critical sections does not
come for free. First, corresponding srcu_read_lock() and
@ -311,12 +355,12 @@ over a rather long period of time, but improvements are always welcome!
destructive operation, and -only- -then- invoke call_rcu(),
synchronize_rcu(), or friends.
Because these primitives only wait for pre-existing readers,
it is the caller's responsibility to guarantee safety to
any subsequent readers.
Because these primitives only wait for pre-existing readers, it
is the caller's responsibility to guarantee that any subsequent
readers will execute safely.
16. The various RCU read-side primitives do -not- contain memory
barriers. The CPU (and in some cases, the compiler) is free
to reorder code into and out of RCU read-side critical sections.
It is the responsibility of the RCU update-side primitives to
deal with this.
16. The various RCU read-side primitives do -not- necessarily contain
memory barriers. You should therefore plan for the CPU
and the compiler to freely reorder code into and out of RCU
read-side critical sections. It is the responsibility of the
RCU update-side primitives to deal with this.

67
Documentation/RCU/lockdep.txt Normal file
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@ -0,0 +1,67 @@
RCU and lockdep checking
All flavors of RCU have lockdep checking available, so that lockdep is
aware of when each task enters and leaves any flavor of RCU read-side
critical section. Each flavor of RCU is tracked separately (but note
that this is not the case in 2.6.32 and earlier). This allows lockdep's
tracking to include RCU state, which can sometimes help when debugging
deadlocks and the like.
In addition, RCU provides the following primitives that check lockdep's
state:
rcu_read_lock_held() for normal RCU.
rcu_read_lock_bh_held() for RCU-bh.
rcu_read_lock_sched_held() for RCU-sched.
srcu_read_lock_held() for SRCU.
These functions are conservative, and will therefore return 1 if they
aren't certain (for example, if CONFIG_DEBUG_LOCK_ALLOC is not set).
This prevents things like WARN_ON(!rcu_read_lock_held()) from giving false
positives when lockdep is disabled.
In addition, a separate kernel config parameter CONFIG_PROVE_RCU enables
checking of rcu_dereference() primitives:
rcu_dereference(p):
Check for RCU read-side critical section.
rcu_dereference_bh(p):
Check for RCU-bh read-side critical section.
rcu_dereference_sched(p):
Check for RCU-sched read-side critical section.
srcu_dereference(p, sp):
Check for SRCU read-side critical section.
rcu_dereference_check(p, c):
Use explicit check expression "c".
rcu_dereference_raw(p)
Don't check. (Use sparingly, if at all.)
The rcu_dereference_check() check expression can be any boolean
expression, but would normally include one of the rcu_read_lock_held()
family of functions and a lockdep expression. However, any boolean
expression can be used. For a moderately ornate example, consider
the following:
file = rcu_dereference_check(fdt->fd[fd],
rcu_read_lock_held() ||
lockdep_is_held(&files->file_lock) ||
atomic_read(&files->count) == 1);
This expression picks up the pointer "fdt->fd[fd]" in an RCU-safe manner,
and, if CONFIG_PROVE_RCU is configured, verifies that this expression
is used in:
1. An RCU read-side critical section, or
2. with files->file_lock held, or
3. on an unshared files_struct.
In case (1), the pointer is picked up in an RCU-safe manner for vanilla
RCU read-side critical sections, in case (2) the ->file_lock prevents
any change from taking place, and finally, in case (3) the current task
is the only task accessing the file_struct, again preventing any change
from taking place.
There are currently only "universal" versions of the rcu_assign_pointer()
and RCU list-/tree-traversal primitives, which do not (yet) check for
being in an RCU read-side critical section. In the future, separate
versions of these primitives might be created.

48
Documentation/RCU/rcu.txt
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@ -75,6 +75,8 @@ o I hear that RCU is patented? What is with that?
search for the string "Patent" in RTFP.txt to find them.
Of these, one was allowed to lapse by the assignee, and the
others have been contributed to the Linux kernel under GPL.
There are now also LGPL implementations of user-level RCU
available (http://lttng.org/?q=node/18).
o I hear that RCU needs work in order to support realtime kernels?
@ -91,48 +93,4 @@ o Where can I find more information on RCU?
o What are all these files in this directory?
NMI-RCU.txt
Describes how to use RCU to implement dynamic
NMI handlers, which can be revectored on the fly,
without rebooting.
RTFP.txt
List of RCU-related publications and web sites.
UP.txt
Discussion of RCU usage in UP kernels.
arrayRCU.txt
Describes how to use RCU to protect arrays, with
resizeable arrays whose elements reference other
data structures being of the most interest.
checklist.txt
Lists things to check for when inspecting code that
uses RCU.
listRCU.txt
Describes how to use RCU to protect linked lists.
This is the simplest and most common use of RCU
in the Linux kernel.
rcu.txt
You are reading it!
rcuref.txt
Describes how to combine use of reference counts
with RCU.
whatisRCU.txt
Overview of how the RCU implementation works. Along
the way, presents a conceptual view of RCU.
See 00-INDEX for the list.

58
Documentation/RCU/stallwarn.txt Normal file
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@ -0,0 +1,58 @@
Using RCU's CPU Stall Detector
The CONFIG_RCU_CPU_STALL_DETECTOR kernel config parameter enables
RCU's CPU stall detector, which detects conditions that unduly delay
RCU grace periods. The stall detector's idea of what constitutes
"unduly delayed" is controlled by a pair of C preprocessor macros:
RCU_SECONDS_TILL_STALL_CHECK
This macro defines the period of time that RCU will wait from
the beginning of a grace period until it issues an RCU CPU
stall warning. It is normally ten seconds.
RCU_SECONDS_TILL_STALL_RECHECK
This macro defines the period of time that RCU will wait after
issuing a stall warning until it issues another stall warning.
It is normally set to thirty seconds.
RCU_STALL_RAT_DELAY
The CPU stall detector tries to make the offending CPU rat on itself,
as this often gives better-quality stack traces. However, if
the offending CPU does not detect its own stall in the number
of jiffies specified by RCU_STALL_RAT_DELAY, then other CPUs will
complain. This is normally set to two jiffies.
The following problems can result in an RCU CPU stall warning:
o A CPU looping in an RCU read-side critical section.
o A CPU looping with interrupts disabled.
o A CPU looping with preemption disabled.
o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel
without invoking schedule().
o A bug in the RCU implementation.
o A hardware failure. This is quite unlikely, but has occurred
at least once in a former life. A CPU failed in a running system,
becoming unresponsive, but not causing an immediate crash.
This resulted in a series of RCU CPU stall warnings, eventually
leading the realization that the CPU had failed.
The RCU, RCU-sched, and RCU-bh implementations have CPU stall warning.
SRCU does not do so directly, but its calls to synchronize_sched() will
result in RCU-sched detecting any CPU stalls that might be occurring.
To diagnose the cause of the stall, inspect the stack traces. The offending
function will usually be near the top of the stack. If you have a series
of stall warnings from a single extended stall, comparing the stack traces
can often help determine where the stall is occurring, which will usually
be in the function nearest the top of the stack that stays the same from
trace to trace.
RCU bugs can often be debugged with the help of CONFIG_RCU_TRACE.

12
Documentation/RCU/torture.txt
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@ -30,6 +30,18 @@ MODULE PARAMETERS
This module has the following parameters:
fqs_duration Duration (in microseconds) of artificially induced bursts
of force_quiescent_state() invocations. In RCU
implementations having force_quiescent_state(), these
bursts help force races between forcing a given grace
period and that grace period ending on its own.
fqs_holdoff Holdoff time (in microseconds) between consecutive calls
to force_quiescent_state() within a burst.
fqs_stutter Wait time (in seconds) between consecutive bursts
of calls to force_quiescent_state().
irqreaders Says to invoke RCU readers from irq level. This is currently
done via timers. Defaults to "1" for variants of RCU that
permit this. (Or, more accurately, variants of RCU that do

16
Documentation/RCU/whatisRCU.txt
View file

@ -323,14 +323,17 @@ used as follows:
Defer Protect
a. synchronize_rcu() rcu_read_lock() / rcu_read_unlock()
call_rcu()
call_rcu() rcu_dereference()
b. call_rcu_bh() rcu_read_lock_bh() / rcu_read_unlock_bh()
rcu_dereference_bh()
c. synchronize_sched() preempt_disable() / preempt_enable()
c. synchronize_sched() rcu_read_lock_sched() / rcu_read_unlock_sched()
preempt_disable() / preempt_enable()
local_irq_save() / local_irq_restore()
hardirq enter / hardirq exit
NMI enter / NMI exit
rcu_dereference_sched()
These three mechanisms are used as follows:
@ -780,9 +783,8 @@ Linux-kernel source code, but it helps to have a full list of the
APIs, since there does not appear to be a way to categorize them
in docbook. Here is the list, by category.
RCU pointer/list traversal:
RCU list traversal:
rcu_dereference
list_for_each_entry_rcu
hlist_for_each_entry_rcu
hlist_nulls_for_each_entry_rcu
@ -808,7 +810,7 @@ RCU: Critical sections Grace period Barrier
rcu_read_lock synchronize_net rcu_barrier
rcu_read_unlock synchronize_rcu
synchronize_rcu_expedited
rcu_dereference synchronize_rcu_expedited
call_rcu
@ -816,7 +818,7 @@ bh: Critical sections Grace period Barrier
rcu_read_lock_bh call_rcu_bh rcu_barrier_bh
rcu_read_unlock_bh synchronize_rcu_bh
synchronize_rcu_bh_expedited
rcu_dereference_bh synchronize_rcu_bh_expedited
sched: Critical sections Grace period Barrier
@ -825,12 +827,14 @@ sched: Critical sections Grace period Barrier
rcu_read_unlock_sched call_rcu_sched
[preempt_disable] synchronize_sched_expedited
[and friends]
rcu_dereference_sched
SRCU: Critical sections Grace period Barrier
srcu_read_lock synchronize_srcu N/A
srcu_read_unlock synchronize_srcu_expedited
srcu_dereference
SRCU: Initialization/cleanup
init_srcu_struct

8
Documentation/SubmitChecklist
View file

@ -9,10 +9,14 @@ Documentation/SubmittingPatches and elsewhere regarding submitting Linux
kernel patches.
1: Builds cleanly with applicable or modified CONFIG options =y, =m, and
1: If you use a facility then #include the file that defines/declares
that facility. Don't depend on other header files pulling in ones
that you use.
2: Builds cleanly with applicable or modified CONFIG options =y, =m, and
=n. No gcc warnings/errors, no linker warnings/errors.
2: Passes allnoconfig, allmodconfig
2b: Passes allnoconfig, allmodconfig
3: Builds on multiple CPU architectures by using local cross-compile tools
or some other build farm.

66
Documentation/acpi/method-customizing.txt Normal file
View file

@ -0,0 +1,66 @@
Linux ACPI Custom Control Method How To
=======================================
Written by Zhang Rui <rui.zhang@intel.com>
Linux supports customizing ACPI control methods at runtime.
Users can use this to
1. override an existing method which may not work correctly,
or just for debugging purposes.
2. insert a completely new method in order to create a missing
method such as _OFF, _ON, _STA, _INI, etc.
For these cases, it is far simpler to dynamically install a single
control method rather than override the entire DSDT, because kernel
rebuild/reboot is not needed and test result can be got in minutes.
Note: Only ACPI METHOD can be overridden, any other object types like
"Device", "OperationRegion", are not recognized.
Note: The same ACPI control method can be overridden for many times,
and it's always the latest one that used by Linux/kernel.
1. override an existing method
a) get the ACPI table via ACPI sysfs I/F. e.g. to get the DSDT,
just run "cat /sys/firmware/acpi/tables/DSDT > /tmp/dsdt.dat"
b) disassemble the table by running "iasl -d dsdt.dat".
c) rewrite the ASL code of the method and save it in a new file,
d) package the new file (psr.asl) to an ACPI table format.
Here is an example of a customized \_SB._AC._PSR method,
DefinitionBlock ("", "SSDT", 1, "", "", 0x20080715)
{
External (ACON)
Method (\_SB_.AC._PSR, 0, NotSerialized)
{
Store ("In AC _PSR", Debug)
Return (ACON)
}
}
Note that the full pathname of the method in ACPI namespace
should be used.
And remember to use "External" to declare external objects.
e) assemble the file to generate the AML code of the method.
e.g. "iasl psr.asl" (psr.aml is generated as a result)
f) mount debugfs by "mount -t debugfs none /sys/kernel/debug"
g) override the old method via the debugfs by running
"cat /tmp/psr.aml > /sys/kernel/debug/acpi/custom_method"
2. insert a new method
This is easier than overriding an existing method.
We just need to create the ASL code of the method we want to
insert and then follow the step c) ~ g) in section 1.
3. undo your changes
The "undo" operation is not supported for a new inserted method
right now, i.e. we can not remove a method currently.
For an overrided method, in order to undo your changes, please
save a copy of the method original ASL code in step c) section 1,
and redo step c) ~ g) to override the method with the original one.
Note: We can use a kernel with multiple custom ACPI method running,
But each individual write to debugfs can implement a SINGLE
method override. i.e. if we want to insert/override multiple
ACPI methods, we need to redo step c) ~ g) for multiple times.

4
Documentation/arm/Samsung-S3C24XX/CPUfreq.txt
View file

@ -14,8 +14,8 @@ Introduction
how the clocks are arranged. The first implementation used as single
PLL to feed the ARM, memory and peripherals via a series of dividers
and muxes and this is the implementation that is documented here. A
newer version where there is a seperate PLL and clock divider for the
ARM core is available as a seperate driver.
newer version where there is a separate PLL and clock divider for the
ARM core is available as a separate driver.
Layout

86
Documentation/arm/Samsung/Overview.txt Normal file
View file

@ -0,0 +1,86 @@
Samsung ARM Linux Overview
==========================
Introduction
------------
The Samsung range of ARM SoCs spans many similar devices, from the initial
ARM9 through to the newest ARM cores. This document shows an overview of
the current kernel support, how to use it and where to find the code
that supports this.
The currently supported SoCs are:
- S3C24XX: See Documentation/arm/Samsung-S3C24XX/Overview.txt for full list
- S3C64XX: S3C6400 and S3C6410
- S5PC6440
S5PC100 and S5PC110 support is currently being merged
S3C24XX Systems
---------------
There is still documentation in Documnetation/arm/Samsung-S3C24XX/ which
deals with the architecture and drivers specific to these devices.
See Documentation/arm/Samsung-S3C24XX/Overview.txt for more information
on the implementation details and specific support.
Configuration
-------------
A number of configurations are supplied, as there is no current way of
unifying all the SoCs into one kernel.
s5p6440_defconfig - S5P6440 specific default configuration
s5pc100_defconfig - S5PC100 specific default configuration
Layout
------
The directory layout is currently being restructured, and consists of
several platform directories and then the machine specific directories
of the CPUs being built for.
plat-samsung provides the base for all the implementations, and is the
last in the line of include directories that are processed for the build
specific information. It contains the base clock, GPIO and device definitions
to get the system running.
plat-s3c is the s3c24xx/s3c64xx platform directory, although it is currently
involved in other builds this will be phased out once the relevant code is
moved elsewhere.
plat-s3c24xx is for s3c24xx specific builds, see the S3C24XX docs.
plat-s3c64xx is for the s3c64xx specific bits, see the S3C24XX docs.
plat-s5p is for s5p specific builds, more to be added.
[ to finish ]
Port Contributors
-----------------
Ben Dooks (BJD)
Vincent Sanders
Herbert Potzl
Arnaud Patard (RTP)
Roc Wu
Klaus Fetscher
Dimitry Andric
Shannon Holland
Guillaume Gourat (NexVision)
Christer Weinigel (wingel) (Acer N30)
Lucas Correia Villa Real (S3C2400 port)
Document Author
---------------
Copyright 2009-2010 Ben Dooks <ben-linux@fluff.org>

167
Documentation/arm/Samsung/clksrc-change-registers.awk Executable file
View file

@ -0,0 +1,167 @@
#!/usr/bin/awk -f
#
# Copyright 2010 Ben Dooks <ben-linux@fluff.org>
#
# Released under GPLv2
# example usage
# ./clksrc-change-registers.awk arch/arm/plat-s5pc1xx/include/plat/regs-clock.h < src > dst
function extract_value(s)
{
eqat = index(s, "=")
comat = index(s, ",")
return substr(s, eqat+2, (comat-eqat)-2)
}
function remove_brackets(b)
{
return substr(b, 2, length(b)-2)
}
function splitdefine(l, p)
{
r = split(l, tp)
p[0] = tp[2]
p[1] = remove_brackets(tp[3])
}
function find_length(f)
{
if (0)
printf "find_length " f "\n" > "/dev/stderr"
if (f ~ /0x1/)
return 1
else if (f ~ /0x3/)
return 2
else if (f ~ /0x7/)
return 3
else if (f ~ /0xf/)
return 4
printf "unknown legnth " f "\n" > "/dev/stderr"
exit
}
function find_shift(s)
{
id = index(s, "<")
if (id <= 0) {
printf "cannot find shift " s "\n" > "/dev/stderr"
exit
}
return substr(s, id+2)
}
BEGIN {
if (ARGC < 2) {
print "too few arguments" > "/dev/stderr"
exit
}
# read the header file and find the mask values that we will need
# to replace and create an associative array of values
while (getline line < ARGV[1] > 0) {
if (line ~ /\#define.*_MASK/ &&
!(line ~ /S5PC100_EPLL_MASK/) &&
!(line ~ /USB_SIG_MASK/)) {
splitdefine(line, fields)
name = fields[0]
if (0)
printf "MASK " line "\n" > "/dev/stderr"
dmask[name,0] = find_length(fields[1])
dmask[name,1] = find_shift(fields[1])
if (0)
printf "=> '" name "' LENGTH=" dmask[name,0] " SHIFT=" dmask[name,1] "\n" > "/dev/stderr"
} else {
}
}
delete ARGV[1]
}
/clksrc_clk.*=.*{/ {
shift=""
mask=""
divshift=""
reg_div=""
reg_src=""
indent=1
print $0
for(; indent >= 1;) {
if ((getline line) <= 0) {
printf "unexpected end of file" > "/dev/stderr"
exit 1;
}
if (line ~ /\.shift/) {
shift = extract_value(line)
} else if (line ~ /\.mask/) {
mask = extract_value(line)
} else if (line ~ /\.reg_divider/) {
reg_div = extract_value(line)
} else if (line ~ /\.reg_source/) {
reg_src = extract_value(line)
} else if (line ~ /\.divider_shift/) {
divshift = extract_value(line)
} else if (line ~ /{/) {
indent++
print line
} else if (line ~ /}/) {
indent--
if (indent == 0) {
if (0) {
printf "shift '" shift "' ='" dmask[shift,0] "'\n" > "/dev/stderr"
printf "mask '" mask "'\n" > "/dev/stderr"
printf "dshft '" divshift "'\n" > "/dev/stderr"
printf "rdiv '" reg_div "'\n" > "/dev/stderr"
printf "rsrc '" reg_src "'\n" > "/dev/stderr"
}
generated = mask
sub(reg_src, reg_div, generated)
if (0) {
printf "/* rsrc " reg_src " */\n"
printf "/* rdiv " reg_div " */\n"
printf "/* shift " shift " */\n"
printf "/* mask " mask " */\n"
printf "/* generated " generated " */\n"
}
if (reg_div != "") {
printf "\t.reg_div = { "
printf ".reg = " reg_div ", "
printf ".shift = " dmask[generated,1] ", "
printf ".size = " dmask[generated,0] ", "
printf "},\n"
}
printf "\t.reg_src = { "
printf ".reg = " reg_src ", "
printf ".shift = " dmask[mask,1] ", "
printf ".size = " dmask[mask,0] ", "
printf "},\n"
}
print line
} else {
print line
}
if (0)
printf indent ":" line "\n" > "/dev/stderr"
}
}
// && ! /clksrc_clk.*=.*{/ { print $0 }

6
Documentation/arm/memory.txt
View file

@ -59,7 +59,11 @@ PAGE_OFFSET high_memory-1 Kernel direct-mapped RAM region.
This maps the platforms RAM, and typically
maps all platform RAM in a 1:1 relationship.
TASK_SIZE PAGE_OFFSET-1 Kernel module space
PKMAP_BASE PAGE_OFFSET-1 Permanent kernel mappings
One way of mapping HIGHMEM pages into kernel
space.
MODULES_VADDR MODULES_END-1 Kernel module space
Kernel modules inserted via insmod are
placed here using dynamic mappings.

3
Documentation/blackfin/00-INDEX
View file

@ -1,9 +1,6 @@
00-INDEX
- This file
cache-lock.txt
- HOWTO for blackfin cache locking.
cachefeatures.txt
- Supported cache features.

6
Documentation/blackfin/Makefile Normal file
View file

@ -0,0 +1,6 @@
obj-m := gptimers-example.o
all: modules
modules clean:
$(MAKE) -C ../.. SUBDIRS=$(PWD) $@

48
Documentation/blackfin/cache-lock.txt
View file

@ -1,48 +0,0 @@
/*
* File: Documentation/blackfin/cache-lock.txt
* Based on:
* Author:
*
* Created:
* Description: This file contains the simple DMA Implementation for Blackfin
*
* Rev: $Id: cache-lock.txt 2384 2006-11-01 04:12:43Z magicyang $
*
* Modified:
* Copyright 2004-2006 Analog Devices Inc.
*
* Bugs: Enter bugs at http://blackfin.uclinux.org/
*
*/
How to lock your code in cache in uClinux/blackfin
--------------------------------------------------
There are only a few steps required to lock your code into the cache.
Currently you can lock the code by Way.
Below are the interface provided for locking the cache.
1. cache_grab_lock(int Ways);
This function grab the lock for locking your code into the cache specified
by Ways.
2. cache_lock(int Ways);
This function should be called after your critical code has been executed.
Once the critical code exits, the code is now loaded into the cache. This
function locks the code into the cache.
So, the example sequence will be:
cache_grab_lock(WAY0_L); /* Grab the lock */
critical_code(); /* Execute the code of interest */
cache_lock(WAY0_L); /* Lock the cache */
Where WAY0_L signifies WAY0 locking.

10
Documentation/blackfin/cachefeatures.txt
View file

@ -41,16 +41,6 @@
icplb_flush();
dcplb_flush();
- Locking the cache.
cache_grab_lock();
cache_lock();
Please refer linux-2.6.x/Documentation/blackfin/cache-lock.txt for how to
lock the cache.
Locking the cache is optional feature.
- Miscellaneous cache functions.
flush_cache_all();

83
Documentation/blackfin/gptimers-example.c Normal file
View file

@ -0,0 +1,83 @@
/*
* Simple gptimers example
* http://docs.blackfin.uclinux.org/doku.php?id=linux-kernel:drivers:gptimers
*
* Copyright 2007-2009 Analog Devices Inc.
*
* Licensed under the GPL-2 or later.
*/
#include <linux/interrupt.h>
#include <linux/module.h>
#include <asm/gptimers.h>
#include <asm/portmux.h>
/* ... random driver includes ... */
#define DRIVER_NAME "gptimer_example"
struct gptimer_data {
uint32_t period, width;
};
static struct gptimer_data data;
/* ... random driver state ... */
static irqreturn_t gptimer_example_irq(int irq, void *dev_id)
{
struct gptimer_data *data = dev_id;
/* make sure it was our timer which caused the interrupt */
if (!get_gptimer_intr(TIMER5_id))
return IRQ_NONE;
/* read the width/period values that were captured for the waveform */
data->width = get_gptimer_pwidth(TIMER5_id);
data->period = get_gptimer_period(TIMER5_id);
/* acknowledge the interrupt */
clear_gptimer_intr(TIMER5_id);
/* tell the upper layers we took care of things */
return IRQ_HANDLED;
}
/* ... random driver code ... */
static int __init gptimer_example_init(void)
{
int ret;
/* grab the peripheral pins */
ret = peripheral_request(P_TMR5, DRIVER_NAME);
if (ret) {
printk(KERN_NOTICE DRIVER_NAME ": peripheral request failed\n");
return ret;
}
/* grab the IRQ for the timer */
ret = request_irq(IRQ_TIMER5, gptimer_example_irq, IRQF_SHARED, DRIVER_NAME, &data);
if (ret) {
printk(KERN_NOTICE DRIVER_NAME ": IRQ request failed\n");
peripheral_free(P_TMR5);
return ret;
}
/* setup the timer and enable it */
set_gptimer_config(TIMER5_id, WDTH_CAP | PULSE_HI | PERIOD_CNT | IRQ_ENA);
enable_gptimers(TIMER5bit);
return 0;
}
module_init(gptimer_example_init);
static void __exit gptimer_example_exit(void)
{
disable_gptimers(TIMER5bit);
free_irq(IRQ_TIMER5, &data);
peripheral_free(P_TMR5);
}
module_exit(gptimer_example_exit);
MODULE_LICENSE("BSD");

2
Documentation/block/00-INDEX
View file

@ -1,7 +1,5 @@
00-INDEX
- This file
as-iosched.txt
- Anticipatory IO scheduler
barrier.txt
- I/O Barriers
biodoc.txt

172
Documentation/block/as-iosched.txt
View file

@ -1,172 +0,0 @@
Anticipatory IO scheduler
-------------------------
Nick Piggin <piggin@cyberone.com.au> 13 Sep 2003
Attention! Database servers, especially those using "TCQ" disks should
investigate performance with the 'deadline' IO scheduler. Any system with high
disk performance requirements should do so, in fact.
If you see unusual performance characteristics of your disk systems, or you
see big performance regressions versus the deadline scheduler, please email
me. Database users don't bother unless you're willing to test a lot of patches
from me ;) its a known issue.
Also, users with hardware RAID controllers, doing striping, may find
highly variable performance results with using the as-iosched. The
as-iosched anticipatory implementation is based on the notion that a disk
device has only one physical seeking head. A striped RAID controller
actually has a head for each physical device in the logical RAID device.
However, setting the antic_expire (see tunable parameters below) produces
very similar behavior to the deadline IO scheduler.
Selecting IO schedulers
-----------------------
Refer to Documentation/block/switching-sched.txt for information on
selecting an io scheduler on a per-device basis.
Anticipatory IO scheduler Policies
----------------------------------
The as-iosched implementation implements several layers of policies
to determine when an IO request is dispatched to the disk controller.
Here are the policies outlined, in order of application.
1. one-way Elevator algorithm.
The elevator algorithm is similar to that used in deadline scheduler, with
the addition that it allows limited backward movement of the elevator
(i.e. seeks backwards). A seek backwards can occur when choosing between
two IO requests where one is behind the elevator's current position, and
the other is in front of the elevator's position. If the seek distance to
the request in back of the elevator is less than half the seek distance to
the request in front of the elevator, then the request in back can be chosen.
Backward seeks are also limited to a maximum of MAXBACK (1024*1024) sectors.
This favors forward movement of the elevator, while allowing opportunistic
"short" backward seeks.
2. FIFO expiration times for reads and for writes.
This is again very similar to the deadline IO scheduler. The expiration
times for requests on these lists is tunable using the parameters read_expire
and write_expire discussed below. When a read or a write expires in this way,
the IO scheduler will interrupt its current elevator sweep or read anticipation
to service the expired request.
3. Read and write request batching
A batch is a collection of read requests or a collection of write
requests. The as scheduler alternates dispatching read and write batches
to the driver. In the case a read batch, the scheduler submits read
requests to the driver as long as there are read requests to submit, and
the read batch time limit has not been exceeded (read_batch_expire).
The read batch time limit begins counting down only when there are
competing write requests pending.
In the case of a write batch, the scheduler submits write requests to
the driver as long as there are write requests available, and the
write batch time limit has not been exceeded (write_batch_expire).
However, the length of write batches will be gradually shortened
when read batches frequently exceed their time limit.
When changing between batch types, the scheduler waits for all requests
from the previous batch to complete before scheduling requests for the
next batch.
The read and write fifo expiration times described in policy 2 above
are checked only when in scheduling IO of a batch for the corresponding
(read/write) type. So for example, the read FIFO timeout values are
tested only during read batches. Likewise, the write FIFO timeout
values are tested only during write batches. For this reason,
it is generally not recommended for the read batch time
to be longer than the write expiration time, nor for the write batch
time to exceed the read expiration time (see tunable parameters below).
When the IO scheduler changes from a read to a write batch,
it begins the elevator from the request that is on the head of the
write expiration FIFO. Likewise, when changing from a write batch to
a read batch, scheduler begins the elevator from the first entry
on the read expiration FIFO.
4. Read anticipation.
Read anticipation occurs only when scheduling a read batch.
This implementation of read anticipation allows only one read request
to be dispatched to the disk controller at a time. In
contrast, many write requests may be dispatched to the disk controller
at a time during a write batch. It is this characteristic that can make
the anticipatory scheduler perform anomalously with controllers supporting
TCQ, or with hardware striped RAID devices. Setting the antic_expire
queue parameter (see below) to zero disables this behavior, and the
anticipatory scheduler behaves essentially like the deadline scheduler.
When read anticipation is enabled (antic_expire is not zero), reads
are dispatched to the disk controller one at a time.
At the end of each read request, the IO scheduler examines its next
candidate read request from its sorted read list. If that next request
is from the same process as the request that just completed,
or if the next request in the queue is "very close" to the
just completed request, it is dispatched immediately. Otherwise,
statistics (average think time, average seek distance) on the process
that submitted the just completed request are examined. If it seems
likely that that process will submit another request soon, and that
request is likely to be near the just completed request, then the IO
scheduler will stop dispatching more read requests for up to (antic_expire)
milliseconds, hoping that process will submit a new request near the one
that just completed. If such a request is made, then it is dispatched
immediately. If the antic_expire wait time expires, then the IO scheduler
will dispatch the next read request from the sorted read queue.
To decide whether an anticipatory wait is worthwhile, the scheduler
maintains statistics for each process that can be used to compute
mean "think time" (the time between read requests), and mean seek
distance for that process. One observation is that these statistics
are associated with each process, but those statistics are not associated
with a specific IO device. So for example, if a process is doing IO
on several file systems on separate devices, the statistics will be
a combination of IO behavior from all those devices.
Tuning the anticipatory IO scheduler
------------------------------------
When using 'as', the anticipatory IO scheduler there are 5 parameters under
/sys/block/*/queue/iosched/. All are units of milliseconds.
The parameters are:
* read_expire
Controls how long until a read request becomes "expired". It also controls the
interval between which expired requests are served, so set to 50, a request
might take anywhere < 100ms to be serviced _if_ it is the next on the
expired list. Obviously request expiration strategies won't make the disk
go faster. The result basically equates to the timeslice a single reader
gets in the presence of other IO. 100*((seek time / read_expire) + 1) is
very roughly the % streaming read efficiency your disk should get with
multiple readers.
* read_batch_expire
Controls how much time a batch of reads is given before pending writes are
served. A higher value is more efficient. This might be set below read_expire
if writes are to be given higher priority than reads, but reads are to be
as efficient as possible when there are no writes. Generally though, it
should be some multiple of read_expire.
* write_expire, and
* write_batch_expire are equivalent to the above, for writes.
* antic_expire
Controls the maximum amount of time we can anticipate a good read (one
with a short seek distance from the most recently completed request) before
giving up. Many other factors may cause anticipation to be stopped early,
or some processes will not be "anticipated" at all. Should be a bit higher
for big seek time devices though not a linear correspondence - most
processes have only a few ms thinktime.
In addition to the tunables above there is a read-only file named est_time
which, when read, will show:
- The probability of a task exiting without a cooperating task
submitting an anticipated IO.
- The current mean think time.
- The seek distance used to determine if an incoming IO is better.

2
Documentation/block/biodoc.txt
View file

@ -186,7 +186,7 @@ a virtual address mapping (unlike the earlier scheme of virtual address
do not have a corresponding kernel virtual address space mapping) and
low-memory pages.
Note: Please refer to Documentation/DMA-mapping.txt for a discussion
Note: Please refer to Documentation/PCI/PCI-DMA-mapping.txt for a discussion
on PCI high mem DMA aspects and mapping of scatter gather lists, and support
for 64 bit PCI.

10
Documentation/block/queue-sysfs.txt
View file

@ -25,11 +25,11 @@ size allowed by the hardware.
nomerges (RW)
-------------
This enables the user to disable the lookup logic involved with IO merging
requests in the block layer. Merging may still occur through a direct
1-hit cache, since that comes for (almost) free. The IO scheduler will not
waste cycles doing tree/hash lookups for merges if nomerges is 1. Defaults
to 0, enabling all merges.
This enables the user to disable the lookup logic involved with IO
merging requests in the block layer. By default (0) all merges are
enabled. When set to 1 only simple one-hit merges will be tried. When
set to 2 no merge algorithms will be tried (including one-hit or more
complex tree/hash lookups).
nr_requests (RW)
----------------

30
Documentation/cachetlb.txt
View file

@ -88,12 +88,12 @@ changes occur:
This is used primarily during fault processing.
5) void update_mmu_cache(struct vm_area_struct *vma,
unsigned long address, pte_t pte)
unsigned long address, pte_t *ptep)
At the end of every page fault, this routine is invoked to
tell the architecture specific code that a translation
described by "pte" now exists at virtual address "address"
for address space "vma->vm_mm", in the software page tables.
now exists at virtual address "address" for address space
"vma->vm_mm", in the software page tables.
A port may use this information in any way it so chooses.
For example, it could use this event to pre-load TLB
@ -377,3 +377,27 @@ maps this page at its virtual address.
All the functionality of flush_icache_page can be implemented in
flush_dcache_page and update_mmu_cache. In 2.7 the hope is to
remove this interface completely.
The final category of APIs is for I/O to deliberately aliased address
ranges inside the kernel. Such aliases are set up by use of the
vmap/vmalloc API. Since kernel I/O goes via physical pages, the I/O
subsystem assumes that the user mapping and kernel offset mapping are
the only aliases. This isn't true for vmap aliases, so anything in
the kernel trying to do I/O to vmap areas must manually manage
coherency. It must do this by flushing the vmap range before doing
I/O and invalidating it after the I/O returns.
void flush_kernel_vmap_range(void *vaddr, int size)
flushes the kernel cache for a given virtual address range in
the vmap area. This is to make sure that any data the kernel
modified in the vmap range is made visible to the physical
page. The design is to make this area safe to perform I/O on.
Note that this API does *not* also flush the offset map alias
of the area.
void invalidate_kernel_vmap_range(void *vaddr, int size) invalidates
the cache for a given virtual address range in the vmap area
which prevents the processor from making the cache stale by
speculatively reading data while the I/O was occurring to the
physical pages. This is only necessary for data reads into the
vmap area.

39
Documentation/cdrom/ide-cd
View file

@ -159,42 +159,7 @@ two arguments: the CDROM device, and the slot number to which you wish
to change. If the slot number is -1, the drive is unloaded.
4. Compilation options
----------------------
There are a few additional options which can be set when compiling the
driver. Most people should not need to mess with any of these; they
are listed here simply for completeness. A compilation option can be
enabled by adding a line of the form `#define <option> 1' to the top
of ide-cd.c. All these options are disabled by default.
VERBOSE_IDE_CD_ERRORS
If this is set, ATAPI error codes will be translated into textual
descriptions. In addition, a dump is made of the command which
provoked the error. This is off by default to save the memory used
by the (somewhat long) table of error descriptions.
STANDARD_ATAPI
If this is set, the code needed to deal with certain drives which do
not properly implement the ATAPI spec will be disabled. If you know
your drive implements ATAPI properly, you can turn this on to get a
slightly smaller kernel.
NO_DOOR_LOCKING
If this is set, the driver will never attempt to lock the door of
the drive.
CDROM_NBLOCKS_BUFFER
This sets the size of the buffer to be used for a CDROMREADAUDIO
ioctl. The default is 8.
TEST
This currently enables an additional ioctl which enables a user-mode
program to execute an arbitrary packet command. See the source for
details. This should be left off unless you know what you're doing.
5. Common problems
4. Common problems
------------------
This section discusses some common problems encountered when trying to
@ -371,7 +336,7 @@ f. Data corruption.
expense of low system performance.
6. cdchange.c
5. cdchange.c
-------------
/*

110
Documentation/cgroups/cgroup_event_listener.c Normal file
View file

@ -0,0 +1,110 @@
/*
* cgroup_event_listener.c - Simple listener of cgroup events
*
* Copyright (C) Kirill A. Shutemov <kirill@shutemov.name>
*/
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/eventfd.h>
#define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>\n"
int main(int argc, char **argv)
{
int efd = -1;
int cfd = -1;
int event_control = -1;
char event_control_path[PATH_MAX];
char line[LINE_MAX];
int ret;
if (argc != 3) {
fputs(USAGE_STR, stderr);
return 1;
}
cfd = open(argv[1], O_RDONLY);
if (cfd == -1) {
fprintf(stderr, "Cannot open %s: %s\n", argv[1],
strerror(errno));
goto out;
}
ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control",
dirname(argv[1]));
if (ret >= PATH_MAX) {
fputs("Path to cgroup.event_control is too long\n", stderr);
goto out;
}
event_control = open(event_control_path, O_WRONLY);
if (event_control == -1) {
fprintf(stderr, "Cannot open %s: %s\n", event_control_path,
strerror(errno));
goto out;
}
efd = eventfd(0, 0);
if (efd == -1) {
perror("eventfd() failed");
goto out;
}
ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);
if (ret >= LINE_MAX) {
fputs("Arguments string is too long\n", stderr);
goto out;
}
ret = write(event_control, line, strlen(line) + 1);
if (ret == -1) {
perror("Cannot write to cgroup.event_control");
goto out;
}
while (1) {
uint64_t result;
ret = read(efd, &result, sizeof(result));
if (ret == -1) {
if (errno == EINTR)
continue;
perror("Cannot read from eventfd");
break;
}
assert(ret == sizeof(result));
ret = access(event_control_path, W_OK);
if ((ret == -1) && (errno == ENOENT)) {
puts("The cgroup seems to have removed.");
ret = 0;
break;
}
if (ret == -1) {
perror("cgroup.event_control "
"is not accessable any more");
break;
}
printf("%s %s: crossed\n", argv[1], argv[2]);
}
out:
if (efd >= 0)
close(efd);
if (event_control >= 0)
close(event_control);
if (cfd >= 0)
close(cfd);
return (ret != 0);
}

39
Documentation/cgroups/cgroups.txt
View file

@ -22,6 +22,8 @@ CONTENTS:
2. Usage Examples and Syntax
2.1 Basic Usage
2.2 Attaching processes
2.3 Mounting hierarchies by name
2.4 Notification API
3. Kernel API
3.1 Overview
3.2 Synchronization
@ -434,6 +436,25 @@ you give a subsystem a name.
The name of the subsystem appears as part of the hierarchy description
in /proc/mounts and /proc/<pid>/cgroups.
2.4 Notification API
--------------------
There is mechanism which allows to get notifications about changing
status of a cgroup.
To register new notification handler you need:
- create a file descriptor for event notification using eventfd(2);
- open a control file to be monitored (e.g. memory.usage_in_bytes);
- write "<event_fd> <control_fd> <args>" to cgroup.event_control.
Interpretation of args is defined by control file implementation;
eventfd will be woken up by control file implementation or when the
cgroup is removed.
To unregister notification handler just close eventfd.
NOTE: Support of notifications should be implemented for the control
file. See documentation for the subsystem.
3. Kernel API
=============
@ -488,6 +509,11 @@ Each subsystem should:
- add an entry in linux/cgroup_subsys.h
- define a cgroup_subsys object called <name>_subsys
If a subsystem can be compiled as a module, it should also have in its
module initcall a call to cgroup_load_subsys(), and in its exitcall a
call to cgroup_unload_subsys(). It should also set its_subsys.module =
THIS_MODULE in its .c file.
Each subsystem may export the following methods. The only mandatory
methods are create/destroy. Any others that are null are presumed to
be successful no-ops.
@ -536,10 +562,21 @@ returns an error, this will abort the attach operation. If a NULL
task is passed, then a successful result indicates that *any*
unspecified task can be moved into the cgroup. Note that this isn't
called on a fork. If this method returns 0 (success) then this should
remain valid while the caller holds cgroup_mutex. If threadgroup is
remain valid while the caller holds cgroup_mutex and it is ensured that either
attach() or cancel_attach() will be called in future. If threadgroup is
true, then a successful result indicates that all threads in the given
thread's threadgroup can be moved together.
void cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct task_struct *task, bool threadgroup)
(cgroup_mutex held by caller)
Called when a task attach operation has failed after can_attach() has succeeded.
A subsystem whose can_attach() has some side-effects should provide this
function, so that the subsytem can implement a rollback. If not, not necessary.
This will be called only about subsystems whose can_attach() operation have
succeeded.
void attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct cgroup *old_cgrp, struct task_struct *task,
bool threadgroup)

127
Documentation/cgroups/cpusets.txt
View file

@ -168,20 +168,20 @@ Each cpuset is represented by a directory in the cgroup file system
containing (on top of the standard cgroup files) the following
files describing that cpuset:
- cpus: list of CPUs in that cpuset
- mems: list of Memory Nodes in that cpuset
- memory_migrate flag: if set, move pages to cpusets nodes
- cpu_exclusive flag: is cpu placement exclusive?
- mem_exclusive flag: is memory placement exclusive?
- mem_hardwall flag: is memory allocation hardwalled
- memory_pressure: measure of how much paging pressure in cpuset
- memory_spread_page flag: if set, spread page cache evenly on allowed nodes
- memory_spread_slab flag: if set, spread slab cache evenly on allowed nodes
- sched_load_balance flag: if set, load balance within CPUs on that cpuset
- sched_relax_domain_level: the searching range when migrating tasks
- cpuset.cpus: list of CPUs in that cpuset
- cpuset.mems: list of Memory Nodes in that cpuset
- cpuset.memory_migrate flag: if set, move pages to cpusets nodes
- cpuset.cpu_exclusive flag: is cpu placement exclusive?
- cpuset.mem_exclusive flag: is memory placement exclusive?
- cpuset.mem_hardwall flag: is memory allocation hardwalled
- cpuset.memory_pressure: measure of how much paging pressure in cpuset
- cpuset.memory_spread_page flag: if set, spread page cache evenly on allowed nodes
- cpuset.memory_spread_slab flag: if set, spread slab cache evenly on allowed nodes
- cpuset.sched_load_balance flag: if set, load balance within CPUs on that cpuset
- cpuset.sched_relax_domain_level: the searching range when migrating tasks
In addition, the root cpuset only has the following file:
- memory_pressure_enabled flag: compute memory_pressure?
- cpuset.memory_pressure_enabled flag: compute memory_pressure?
New cpusets are created using the mkdir system call or shell
command. The properties of a cpuset, such as its flags, allowed
@ -229,7 +229,7 @@ If a cpuset is cpu or mem exclusive, no other cpuset, other than
a direct ancestor or descendant, may share any of the same CPUs or
Memory Nodes.
A cpuset that is mem_exclusive *or* mem_hardwall is "hardwalled",
A cpuset that is cpuset.mem_exclusive *or* cpuset.mem_hardwall is "hardwalled",
i.e. it restricts kernel allocations for page, buffer and other data
commonly shared by the kernel across multiple users. All cpusets,
whether hardwalled or not, restrict allocations of memory for user
@ -304,15 +304,15 @@ times 1000.
---------------------------
There are two boolean flag files per cpuset that control where the
kernel allocates pages for the file system buffers and related in
kernel data structures. They are called 'memory_spread_page' and
'memory_spread_slab'.
kernel data structures. They are called 'cpuset.memory_spread_page' and
'cpuset.memory_spread_slab'.
If the per-cpuset boolean flag file 'memory_spread_page' is set, then
If the per-cpuset boolean flag file 'cpuset.memory_spread_page' is set, then
the kernel will spread the file system buffers (page cache) evenly
over all the nodes that the faulting task is allowed to use, instead
of preferring to put those pages on the node where the task is running.
If the per-cpuset boolean flag file 'memory_spread_slab' is set,
If the per-cpuset boolean flag file 'cpuset.memory_spread_slab' is set,
then the kernel will spread some file system related slab caches,
such as for inodes and dentries evenly over all the nodes that the
faulting task is allowed to use, instead of preferring to put those
@ -337,21 +337,21 @@ their containing tasks memory spread settings. If memory spreading
is turned off, then the currently specified NUMA mempolicy once again
applies to memory page allocations.
Both 'memory_spread_page' and 'memory_spread_slab' are boolean flag
Both 'cpuset.memory_spread_page' and 'cpuset.memory_spread_slab' are boolean flag
files. By default they contain "0", meaning that the feature is off
for that cpuset. If a "1" is written to that file, then that turns
the named feature on.
The implementation is simple.
Setting the flag 'memory_spread_page' turns on a per-process flag
Setting the flag 'cpuset.memory_spread_page' turns on a per-process flag
PF_SPREAD_PAGE for each task that is in that cpuset or subsequently
joins that cpuset. The page allocation calls for the page cache
is modified to perform an inline check for this PF_SPREAD_PAGE task
flag, and if set, a call to a new routine cpuset_mem_spread_node()
returns the node to prefer for the allocation.
Similarly, setting 'memory_spread_slab' turns on the flag
Similarly, setting 'cpuset.memory_spread_slab' turns on the flag
PF_SPREAD_SLAB, and appropriately marked slab caches will allocate
pages from the node returned by cpuset_mem_spread_node().
@ -404,24 +404,24 @@ the following two situations:
system overhead on those CPUs, including avoiding task load
balancing if that is not needed.
When the per-cpuset flag "sched_load_balance" is enabled (the default
setting), it requests that all the CPUs in that cpusets allowed 'cpus'
When the per-cpuset flag "cpuset.sched_load_balance" is enabled (the default
setting), it requests that all the CPUs in that cpusets allowed 'cpuset.cpus'
be contained in a single sched domain, ensuring that load balancing
can move a task (not otherwised pinned, as by sched_setaffinity)
from any CPU in that cpuset to any other.
When the per-cpuset flag "sched_load_balance" is disabled, then the
When the per-cpuset flag "cpuset.sched_load_balance" is disabled, then the
scheduler will avoid load balancing across the CPUs in that cpuset,
--except-- in so far as is necessary because some overlapping cpuset
has "sched_load_balance" enabled.
So, for example, if the top cpuset has the flag "sched_load_balance"
So, for example, if the top cpuset has the flag "cpuset.sched_load_balance"
enabled, then the scheduler will have one sched domain covering all
CPUs, and the setting of the "sched_load_balance" flag in any other
CPUs, and the setting of the "cpuset.sched_load_balance" flag in any other
cpusets won't matter, as we're already fully load balancing.
Therefore in the above two situations, the top cpuset flag
"sched_load_balance" should be disabled, and only some of the smaller,
"cpuset.sched_load_balance" should be disabled, and only some of the smaller,
child cpusets have this flag enabled.
When doing this, you don't usually want to leave any unpinned tasks in
@ -433,7 +433,7 @@ scheduler might not consider the possibility of load balancing that
task to that underused CPU.
Of course, tasks pinned to a particular CPU can be left in a cpuset
that disables "sched_load_balance" as those tasks aren't going anywhere
that disables "cpuset.sched_load_balance" as those tasks aren't going anywhere
else anyway.
There is an impedance mismatch here, between cpusets and sched domains.
@ -443,19 +443,19 @@ overlap and each CPU is in at most one sched domain.
It is necessary for sched domains to be flat because load balancing
across partially overlapping sets of CPUs would risk unstable dynamics
that would be beyond our understanding. So if each of two partially
overlapping cpusets enables the flag 'sched_load_balance', then we
overlapping cpusets enables the flag 'cpuset.sched_load_balance', then we
form a single sched domain that is a superset of both. We won't move
a task to a CPU outside it cpuset, but the scheduler load balancing
code might waste some compute cycles considering that possibility.
This mismatch is why there is not a simple one-to-one relation
between which cpusets have the flag "sched_load_balance" enabled,
between which cpusets have the flag "cpuset.sched_load_balance" enabled,
and the sched domain configuration. If a cpuset enables the flag, it
will get balancing across all its CPUs, but if it disables the flag,
it will only be assured of no load balancing if no other overlapping
cpuset enables the flag.
If two cpusets have partially overlapping 'cpus' allowed, and only
If two cpusets have partially overlapping 'cpuset.cpus' allowed, and only
one of them has this flag enabled, then the other may find its
tasks only partially load balanced, just on the overlapping CPUs.
This is just the general case of the top_cpuset example given a few
@ -468,23 +468,23 @@ load balancing to the other CPUs.
1.7.1 sched_load_balance implementation details.
------------------------------------------------
The per-cpuset flag 'sched_load_balance' defaults to enabled (contrary
The per-cpuset flag 'cpuset.sched_load_balance' defaults to enabled (contrary
to most cpuset flags.) When enabled for a cpuset, the kernel will
ensure that it can load balance across all the CPUs in that cpuset
(makes sure that all the CPUs in the cpus_allowed of that cpuset are
in the same sched domain.)
If two overlapping cpusets both have 'sched_load_balance' enabled,
If two overlapping cpusets both have 'cpuset.sched_load_balance' enabled,
then they will be (must be) both in the same sched domain.
If, as is the default, the top cpuset has 'sched_load_balance' enabled,
If, as is the default, the top cpuset has 'cpuset.sched_load_balance' enabled,
then by the above that means there is a single sched domain covering
the whole system, regardless of any other cpuset settings.
The kernel commits to user space that it will avoid load balancing
where it can. It will pick as fine a granularity partition of sched
domains as it can while still providing load balancing for any set
of CPUs allowed to a cpuset having 'sched_load_balance' enabled.
of CPUs allowed to a cpuset having 'cpuset.sched_load_balance' enabled.
The internal kernel cpuset to scheduler interface passes from the
cpuset code to the scheduler code a partition of the load balanced
@ -495,9 +495,9 @@ all the CPUs that must be load balanced.
The cpuset code builds a new such partition and passes it to the
scheduler sched domain setup code, to have the sched domains rebuilt
as necessary, whenever:
- the 'sched_load_balance' flag of a cpuset with non-empty CPUs changes,
- the 'cpuset.sched_load_balance' flag of a cpuset with non-empty CPUs changes,
- or CPUs come or go from a cpuset with this flag enabled,
- or 'sched_relax_domain_level' value of a cpuset with non-empty CPUs
- or 'cpuset.sched_relax_domain_level' value of a cpuset with non-empty CPUs
and with this flag enabled changes,
- or a cpuset with non-empty CPUs and with this flag enabled is removed,
- or a cpu is offlined/onlined.
@ -542,7 +542,7 @@ As the result, task B on CPU X need to wait task A or wait load balance
on the next tick. For some applications in special situation, waiting
1 tick may be too long.
The 'sched_relax_domain_level' file allows you to request changing
The 'cpuset.sched_relax_domain_level' file allows you to request changing
this searching range as you like. This file takes int value which
indicates size of searching range in levels ideally as follows,
otherwise initial value -1 that indicates the cpuset has no request.
@ -559,8 +559,8 @@ The system default is architecture dependent. The system default
can be changed using the relax_domain_level= boot parameter.
This file is per-cpuset and affect the sched domain where the cpuset
belongs to. Therefore if the flag 'sched_load_balance' of a cpuset
is disabled, then 'sched_relax_domain_level' have no effect since
belongs to. Therefore if the flag 'cpuset.sched_load_balance' of a cpuset
is disabled, then 'cpuset.sched_relax_domain_level' have no effect since
there is no sched domain belonging the cpuset.
If multiple cpusets are overlapping and hence they form a single sched
@ -607,9 +607,9 @@ from one cpuset to another, then the kernel will adjust the tasks
memory placement, as above, the next time that the kernel attempts
to allocate a page of memory for that task.
If a cpuset has its 'cpus' modified, then each task in that cpuset
If a cpuset has its 'cpuset.cpus' modified, then each task in that cpuset
will have its allowed CPU placement changed immediately. Similarly,
if a tasks pid is written to another cpusets 'tasks' file, then its
if a tasks pid is written to another cpusets 'cpuset.tasks' file, then its
allowed CPU placement is changed immediately. If such a task had been
bound to some subset of its cpuset using the sched_setaffinity() call,
the task will be allowed to run on any CPU allowed in its new cpuset,
@ -622,8 +622,8 @@ and the processor placement is updated immediately.
Normally, once a page is allocated (given a physical page
of main memory) then that page stays on whatever node it
was allocated, so long as it remains allocated, even if the
cpusets memory placement policy 'mems' subsequently changes.
If the cpuset flag file 'memory_migrate' is set true, then when
cpusets memory placement policy 'cpuset.mems' subsequently changes.
If the cpuset flag file 'cpuset.memory_migrate' is set true, then when
tasks are attached to that cpuset, any pages that task had
allocated to it on nodes in its previous cpuset are migrated
to the tasks new cpuset. The relative placement of the page within
@ -631,12 +631,12 @@ the cpuset is preserved during these migration operations if possible.
For example if the page was on the second valid node of the prior cpuset
then the page will be placed on the second valid node of the new cpuset.
Also if 'memory_migrate' is set true, then if that cpusets
'mems' file is modified, pages allocated to tasks in that
cpuset, that were on nodes in the previous setting of 'mems',
Also if 'cpuset.memory_migrate' is set true, then if that cpusets
'cpuset.mems' file is modified, pages allocated to tasks in that
cpuset, that were on nodes in the previous setting of 'cpuset.mems',
will be moved to nodes in the new setting of 'mems.'
Pages that were not in the tasks prior cpuset, or in the cpusets
prior 'mems' setting, will not be moved.
prior 'cpuset.mems' setting, will not be moved.
There is an exception to the above. If hotplug functionality is used
to remove all the CPUs that are currently assigned to a cpuset,
@ -678,8 +678,8 @@ and then start a subshell 'sh' in that cpuset:
cd /dev/cpuset
mkdir Charlie
cd Charlie
/bin/echo 2-3 > cpus
/bin/echo 1 > mems
/bin/echo 2-3 > cpuset.cpus
/bin/echo 1 > cpuset.mems
/bin/echo $$ > tasks
sh
# The subshell 'sh' is now running in cpuset Charlie
@ -725,10 +725,13 @@ Now you want to do something with this cpuset.
In this directory you can find several files:
# ls
cpu_exclusive memory_migrate mems tasks
cpus memory_pressure notify_on_release
mem_exclusive memory_spread_page sched_load_balance
mem_hardwall memory_spread_slab sched_relax_domain_level
cpuset.cpu_exclusive cpuset.memory_spread_slab
cpuset.cpus cpuset.mems
cpuset.mem_exclusive cpuset.sched_load_balance
cpuset.mem_hardwall cpuset.sched_relax_domain_level
cpuset.memory_migrate notify_on_release
cpuset.memory_pressure tasks
cpuset.memory_spread_page
Reading them will give you information about the state of this cpuset:
the CPUs and Memory Nodes it can use, the processes that are using
@ -736,13 +739,13 @@ it, its properties. By writing to these files you can manipulate
the cpuset.
Set some flags:
# /bin/echo 1 > cpu_exclusive
# /bin/echo 1 > cpuset.cpu_exclusive
Add some cpus:
# /bin/echo 0-7 > cpus
# /bin/echo 0-7 > cpuset.cpus
Add some mems:
# /bin/echo 0-7 > mems
# /bin/echo 0-7 > cpuset.mems
Now attach your shell to this cpuset:
# /bin/echo $$ > tasks
@ -774,28 +777,28 @@ echo "/sbin/cpuset_release_agent" > /dev/cpuset/release_agent
This is the syntax to use when writing in the cpus or mems files
in cpuset directories:
# /bin/echo 1-4 > cpus -> set cpus list to cpus 1,2,3,4
# /bin/echo 1,2,3,4 > cpus -> set cpus list to cpus 1,2,3,4
# /bin/echo 1-4 > cpuset.cpus -> set cpus list to cpus 1,2,3,4
# /bin/echo 1,2,3,4 > cpuset.cpus -> set cpus list to cpus 1,2,3,4
To add a CPU to a cpuset, write the new list of CPUs including the
CPU to be added. To add 6 to the above cpuset:
# /bin/echo 1-4,6 > cpus -> set cpus list to cpus 1,2,3,4,6
# /bin/echo 1-4,6 > cpuset.cpus -> set cpus list to cpus 1,2,3,4,6
Similarly to remove a CPU from a cpuset, write the new list of CPUs
without the CPU to be removed.
To remove all the CPUs:
# /bin/echo "" > cpus -> clear cpus list
# /bin/echo "" > cpuset.cpus -> clear cpus list
2.3 Setting flags
-----------------
The syntax is very simple:
# /bin/echo 1 > cpu_exclusive -> set flag 'cpu_exclusive'
# /bin/echo 0 > cpu_exclusive -> unset flag 'cpu_exclusive'
# /bin/echo 1 > cpuset.cpu_exclusive -> set flag 'cpuset.cpu_exclusive'
# /bin/echo 0 > cpuset.cpu_exclusive -> unset flag 'cpuset.cpu_exclusive'
2.4 Attaching processes
-----------------------

47
Documentation/cgroups/memcg_test.txt
View file

@ -1,6 +1,6 @@
Memory Resource Controller(Memcg) Implementation Memo.
Last Updated: 2009/1/20
Base Kernel Version: based on 2.6.29-rc2.
Last Updated: 2010/2
Base Kernel Version: based on 2.6.33-rc7-mm(candidate for 34).
Because VM is getting complex (one of reasons is memcg...), memcg's behavior
is complex. This is a document for memcg's internal behavior.
@ -337,7 +337,7 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y.
race and lock dependency with other cgroup subsystems.
example)
# mount -t cgroup none /cgroup -t cpuset,memory,cpu,devices
# mount -t cgroup none /cgroup -o cpuset,memory,cpu,devices
and do task move, mkdir, rmdir etc...under this.
@ -348,7 +348,7 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y.
For example, test like following is good.
(Shell-A)
# mount -t cgroup none /cgroup -t memory
# mount -t cgroup none /cgroup -o memory
# mkdir /cgroup/test
# echo 40M > /cgroup/test/memory.limit_in_bytes
# echo 0 > /cgroup/test/tasks
@ -378,3 +378,42 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y.
#echo 50M > memory.limit_in_bytes
#echo 50M > memory.memsw.limit_in_bytes
run 51M of malloc
9.9 Move charges at task migration
Charges associated with a task can be moved along with task migration.
(Shell-A)
#mkdir /cgroup/A
#echo $$ >/cgroup/A/tasks
run some programs which uses some amount of memory in /cgroup/A.
(Shell-B)
#mkdir /cgroup/B
#echo 1 >/cgroup/B/memory.move_charge_at_immigrate
#echo "pid of the program running in group A" >/cgroup/B/tasks
You can see charges have been moved by reading *.usage_in_bytes or
memory.stat of both A and B.
See 8.2 of Documentation/cgroups/memory.txt to see what value should be
written to move_charge_at_immigrate.
9.10 Memory thresholds
Memory controler implements memory thresholds using cgroups notification
API. You can use Documentation/cgroups/cgroup_event_listener.c to test
it.
(Shell-A) Create cgroup and run event listener
# mkdir /cgroup/A
# ./cgroup_event_listener /cgroup/A/memory.usage_in_bytes 5M
(Shell-B) Add task to cgroup and try to allocate and free memory
# echo $$ >/cgroup/A/tasks
# a="$(dd if=/dev/zero bs=1M count=10)"
# a=
You will see message from cgroup_event_listener every time you cross
the thresholds.
Use /cgroup/A/memory.memsw.usage_in_bytes to test memsw thresholds.
It's good idea to test root cgroup as well.

82
Documentation/cgroups/memory.txt
View file

@ -182,6 +182,8 @@ list.
NOTE: Reclaim does not work for the root cgroup, since we cannot set any
limits on the root cgroup.
Note2: When panic_on_oom is set to "2", the whole system will panic.
2. Locking
The memory controller uses the following hierarchy
@ -262,10 +264,12 @@ some of the pages cached in the cgroup (page cache pages).
4.2 Task migration
When a task migrates from one cgroup to another, it's charge is not
carried forward. The pages allocated from the original cgroup still
carried forward by default. The pages allocated from the original cgroup still
remain charged to it, the charge is dropped when the page is freed or
reclaimed.
Note: You can move charges of a task along with task migration. See 8.
4.3 Removing a cgroup
A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a
@ -336,7 +340,7 @@ Note:
5.3 swappiness
Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only.
Following cgroups' swapiness can't be changed.
Following cgroups' swappiness can't be changed.
- root cgroup (uses /proc/sys/vm/swappiness).
- a cgroup which uses hierarchy and it has child cgroup.
- a cgroup which uses hierarchy and not the root of hierarchy.
@ -377,7 +381,8 @@ The feature can be disabled by
NOTE1: Enabling/disabling will fail if the cgroup already has other
cgroups created below it.
NOTE2: This feature can be enabled/disabled per subtree.
NOTE2: When panic_on_oom is set to "2", the whole system will panic in
case of an oom event in any cgroup.
7. Soft limits
@ -414,7 +419,76 @@ NOTE1: Soft limits take effect over a long period of time, since they involve
NOTE2: It is recommended to set the soft limit always below the hard limit,
otherwise the hard limit will take precedence.
8. TODO
8. Move charges at task migration
Users can move charges associated with a task along with task migration, that
is, uncharge task's pages from the old cgroup and charge them to the new cgroup.
This feature is not supported in !CONFIG_MMU environments because of lack of
page tables.
8.1 Interface
This feature is disabled by default. It can be enabled(and disabled again) by
writing to memory.move_charge_at_immigrate of the destination cgroup.
If you want to enable it:
# echo (some positive value) > memory.move_charge_at_immigrate
Note: Each bits of move_charge_at_immigrate has its own meaning about what type
of charges should be moved. See 8.2 for details.
Note: Charges are moved only when you move mm->owner, IOW, a leader of a thread
group.
Note: If we cannot find enough space for the task in the destination cgroup, we
try to make space by reclaiming memory. Task migration may fail if we
cannot make enough space.
Note: It can take several seconds if you move charges in giga bytes order.
And if you want disable it again:
# echo 0 > memory.move_charge_at_immigrate
8.2 Type of charges which can be move
Each bits of move_charge_at_immigrate has its own meaning about what type of
charges should be moved.
bit | what type of charges would be moved ?
-----+------------------------------------------------------------------------
0 | A charge of an anonymous page(or swap of it) used by the target task.
| Those pages and swaps must be used only by the target task. You must
| enable Swap Extension(see 2.4) to enable move of swap charges.
Note: Those pages and swaps must be charged to the old cgroup.
Note: More type of pages(e.g. file cache, shmem,) will be supported by other
bits in future.
8.3 TODO
- Add support for other types of pages(e.g. file cache, shmem, etc.).
- Implement madvise(2) to let users decide the vma to be moved or not to be
moved.
- All of moving charge operations are done under cgroup_mutex. It's not good
behavior to hold the mutex too long, so we may need some trick.
9. Memory thresholds
Memory controler implements memory thresholds using cgroups notification
API (see cgroups.txt). It allows to register multiple memory and memsw
thresholds and gets notifications when it crosses.
To register a threshold application need:
- create an eventfd using eventfd(2);
- open memory.usage_in_bytes or memory.memsw.usage_in_bytes;
- write string like "<event_fd> <memory.usage_in_bytes> <threshold>" to
cgroup.event_control.
Application will be notified through eventfd when memory usage crosses
threshold in any direction.
It's applicable for root and non-root cgroup.
10. TODO
1. Add support for accounting huge pages (as a separate controller)
2. Make per-cgroup scanner reclaim not-shared pages first

234
Documentation/circular-buffers.txt Normal file
View file

@ -0,0 +1,234 @@
================
CIRCULAR BUFFERS
================
By: David Howells <dhowells@redhat.com>
Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Linux provides a number of features that can be used to implement circular
buffering. There are two sets of such features:
(1) Convenience functions for determining information about power-of-2 sized
buffers.
(2) Memory barriers for when the producer and the consumer of objects in the
buffer don't want to share a lock.
To use these facilities, as discussed below, there needs to be just one
producer and just one consumer. It is possible to handle multiple producers by
serialising them, and to handle multiple consumers by serialising them.
Contents:
(*) What is a circular buffer?
(*) Measuring power-of-2 buffers.
(*) Using memory barriers with circular buffers.
- The producer.
- The consumer.
==========================
WHAT IS A CIRCULAR BUFFER?
==========================
First of all, what is a circular buffer? A circular buffer is a buffer of
fixed, finite size into which there are two indices:
(1) A 'head' index - the point at which the producer inserts items into the
buffer.
(2) A 'tail' index - the point at which the consumer finds the next item in
the buffer.
Typically when the tail pointer is equal to the head pointer, the buffer is
empty; and the buffer is full when the head pointer is one less than the tail
pointer.
The head index is incremented when items are added, and the tail index when
items are removed. The tail index should never jump the head index, and both
indices should be wrapped to 0 when they reach the end of the buffer, thus
allowing an infinite amount of data to flow through the buffer.
Typically, items will all be of the same unit size, but this isn't strictly
required to use the techniques below. The indices can be increased by more
than 1 if multiple items or variable-sized items are to be included in the
buffer, provided that neither index overtakes the other. The implementer must
be careful, however, as a region more than one unit in size may wrap the end of
the buffer and be broken into two segments.
============================
MEASURING POWER-OF-2 BUFFERS
============================
Calculation of the occupancy or the remaining capacity of an arbitrarily sized
circular buffer would normally be a slow operation, requiring the use of a
modulus (divide) instruction. However, if the buffer is of a power-of-2 size,
then a much quicker bitwise-AND instruction can be used instead.
Linux provides a set of macros for handling power-of-2 circular buffers. These
can be made use of by:
#include <linux/circ_buf.h>
The macros are:
(*) Measure the remaining capacity of a buffer:
CIRC_SPACE(head_index, tail_index, buffer_size);
This returns the amount of space left in the buffer[1] into which items
can be inserted.
(*) Measure the maximum consecutive immediate space in a buffer:
CIRC_SPACE_TO_END(head_index, tail_index, buffer_size);
This returns the amount of consecutive space left in the buffer[1] into
which items can be immediately inserted without having to wrap back to the
beginning of the buffer.
(*) Measure the occupancy of a buffer:
CIRC_CNT(head_index, tail_index, buffer_size);
This returns the number of items currently occupying a buffer[2].
(*) Measure the non-wrapping occupancy of a buffer:
CIRC_CNT_TO_END(head_index, tail_index, buffer_size);
This returns the number of consecutive items[2] that can be extracted from
the buffer without having to wrap back to the beginning of the buffer.
Each of these macros will nominally return a value between 0 and buffer_size-1,
however:
[1] CIRC_SPACE*() are intended to be used in the producer. To the producer
they will return a lower bound as the producer controls the head index,
but the consumer may still be depleting the buffer on another CPU and
moving the tail index.
To the consumer it will show an upper bound as the producer may be busy
depleting the space.
[2] CIRC_CNT*() are intended to be used in the consumer. To the consumer they
will return a lower bound as the consumer controls the tail index, but the
producer may still be filling the buffer on another CPU and moving the
head index.
To the producer it will show an upper bound as the consumer may be busy
emptying the buffer.
[3] To a third party, the order in which the writes to the indices by the
producer and consumer become visible cannot be guaranteed as they are
independent and may be made on different CPUs - so the result in such a
situation will merely be a guess, and may even be negative.
===========================================
USING MEMORY BARRIERS WITH CIRCULAR BUFFERS
===========================================
By using memory barriers in conjunction with circular buffers, you can avoid
the need to:
(1) use a single lock to govern access to both ends of the buffer, thus
allowing the buffer to be filled and emptied at the same time; and
(2) use atomic counter operations.
There are two sides to this: the producer that fills the buffer, and the
consumer that empties it. Only one thing should be filling a buffer at any one
time, and only one thing should be emptying a buffer at any one time, but the
two sides can operate simultaneously.
THE PRODUCER
------------
The producer will look something like this:
spin_lock(&producer_lock);
unsigned long head = buffer->head;
unsigned long tail = ACCESS_ONCE(buffer->tail);
if (CIRC_SPACE(head, tail, buffer->size) >= 1) {
/* insert one item into the buffer */
struct item *item = buffer[head];
produce_item(item);
smp_wmb(); /* commit the item before incrementing the head */
buffer->head = (head + 1) & (buffer->size - 1);
/* wake_up() will make sure that the head is committed before
* waking anyone up */
wake_up(consumer);
}
spin_unlock(&producer_lock);
This will instruct the CPU that the contents of the new item must be written
before the head index makes it available to the consumer and then instructs the
CPU that the revised head index must be written before the consumer is woken.
Note that wake_up() doesn't have to be the exact mechanism used, but whatever
is used must guarantee a (write) memory barrier between the update of the head
index and the change of state of the consumer, if a change of state occurs.
THE CONSUMER
------------
The consumer will look something like this:
spin_lock(&consumer_lock);
unsigned long head = ACCESS_ONCE(buffer->head);
unsigned long tail = buffer->tail;
if (CIRC_CNT(head, tail, buffer->size) >= 1) {
/* read index before reading contents at that index */
smp_read_barrier_depends();
/* extract one item from the buffer */
struct item *item = buffer[tail];
consume_item(item);
smp_mb(); /* finish reading descriptor before incrementing tail */
buffer->tail = (tail + 1) & (buffer->size - 1);
}
spin_unlock(&consumer_lock);
This will instruct the CPU to make sure the index is up to date before reading
the new item, and then it shall make sure the CPU has finished reading the item
before it writes the new tail pointer, which will erase the item.
Note the use of ACCESS_ONCE() in both algorithms to read the opposition index.
This prevents the compiler from discarding and reloading its cached value -
which some compilers will do across smp_read_barrier_depends(). This isn't
strictly needed if you can be sure that the opposition index will _only_ be
used the once.
===============
FURTHER READING
===============
See also Documentation/memory-barriers.txt for a description of Linux's memory
barrier facilities.

2
Documentation/console/console.txt
View file

@ -74,7 +74,7 @@ driver takes over the consoles vacated by the driver. Binding, on the other
hand, will bind the driver to the consoles that are currently occupied by a
system driver.
NOTE1: Binding and binding must be selected in Kconfig. It's under:
NOTE1: Binding and unbinding must be selected in Kconfig. It's under:
Device Drivers -> Character devices -> Support for binding and unbinding
console drivers

4
Documentation/cpu-freq/governors.txt
View file

@ -145,8 +145,8 @@ show_sampling_rate_max: THIS INTERFACE IS DEPRECATED, DON'T USE IT.
up_threshold: defines what the average CPU usage between the samplings
of 'sampling_rate' needs to be for the kernel to make a decision on
whether it should increase the frequency. For example when it is set
to its default value of '80' it means that between the checking
intervals the CPU needs to be on average more than 80% in use to then
to its default value of '95' it means that between the checking
intervals the CPU needs to be on average more than 95% in use to then
decide that the CPU frequency needs to be increased.
ignore_nice_load: this parameter takes a value of '0' or '1'. When

207
Documentation/cpu-freq/pcc-cpufreq.txt Normal file
View file

@ -0,0 +1,207 @@
/*
* pcc-cpufreq.txt - PCC interface documentation
*
* Copyright (C) 2009 Red Hat, Matthew Garrett <mjg@redhat.com>
* Copyright (C) 2009 Hewlett-Packard Development Company, L.P.
* Nagananda Chumbalkar <nagananda.chumbalkar@hp.com>
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or NON
* INFRINGEMENT. See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 675 Mass Ave, Cambridge, MA 02139, USA.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
Processor Clocking Control Driver
---------------------------------
Contents:
---------
1. Introduction
1.1 PCC interface
1.1.1 Get Average Frequency
1.1.2 Set Desired Frequency
1.2 Platforms affected
2. Driver and /sys details
2.1 scaling_available_frequencies
2.2 cpuinfo_transition_latency
2.3 cpuinfo_cur_freq
2.4 related_cpus
3. Caveats
1. Introduction:
----------------
Processor Clocking Control (PCC) is an interface between the platform
firmware and OSPM. It is a mechanism for coordinating processor
performance (ie: frequency) between the platform firmware and the OS.
The PCC driver (pcc-cpufreq) allows OSPM to take advantage of the PCC
interface.
OS utilizes the PCC interface to inform platform firmware what frequency the
OS wants for a logical processor. The platform firmware attempts to achieve
the requested frequency. If the request for the target frequency could not be
satisfied by platform firmware, then it usually means that power budget
conditions are in place, and "power capping" is taking place.
1.1 PCC interface:
------------------
The complete PCC specification is available here:
http://www.acpica.org/download/Processor-Clocking-Control-v1p0.pdf
PCC relies on a shared memory region that provides a channel for communication
between the OS and platform firmware. PCC also implements a "doorbell" that
is used by the OS to inform the platform firmware that a command has been
sent.
The ACPI PCCH() method is used to discover the location of the PCC shared
memory region. The shared memory region header contains the "command" and
"status" interface. PCCH() also contains details on how to access the platform
doorbell.
The following commands are supported by the PCC interface:
* Get Average Frequency
* Set Desired Frequency
The ACPI PCCP() method is implemented for each logical processor and is
used to discover the offsets for the input and output buffers in the shared
memory region.
When PCC mode is enabled, the platform will not expose processor performance
or throttle states (_PSS, _TSS and related ACPI objects) to OSPM. Therefore,
the native P-state driver (such as acpi-cpufreq for Intel, powernow-k8 for
AMD) will not load.
However, OSPM remains in control of policy. The governor (eg: "ondemand")
computes the required performance for each processor based on server workload.
The PCC driver fills in the command interface, and the input buffer and
communicates the request to the platform firmware. The platform firmware is
responsible for delivering the requested performance.
Each PCC command is "global" in scope and can affect all the logical CPUs in
the system. Therefore, PCC is capable of performing "group" updates. With PCC
the OS is capable of getting/setting the frequency of all the logical CPUs in
the system with a single call to the BIOS.
1.1.1 Get Average Frequency:
----------------------------
This command is used by the OSPM to query the running frequency of the
processor since the last time this command was completed. The output buffer
indicates the average unhalted frequency of the logical processor expressed as
a percentage of the nominal (ie: maximum) CPU frequency. The output buffer
also signifies if the CPU frequency is limited by a power budget condition.
1.1.2 Set Desired Frequency:
----------------------------
This command is used by the OSPM to communicate to the platform firmware the
desired frequency for a logical processor. The output buffer is currently
ignored by OSPM. The next invocation of "Get Average Frequency" will inform
OSPM if the desired frequency was achieved or not.
1.2 Platforms affected:
-----------------------
The PCC driver will load on any system where the platform firmware:
* supports the PCC interface, and the associated PCCH() and PCCP() methods
* assumes responsibility for managing the hardware clocking controls in order
to deliver the requested processor performance
Currently, certain HP ProLiant platforms implement the PCC interface. On those
platforms PCC is the "default" choice.
However, it is possible to disable this interface via a BIOS setting. In
such an instance, as is also the case on platforms where the PCC interface
is not implemented, the PCC driver will fail to load silently.
2. Driver and /sys details:
---------------------------
When the driver loads, it merely prints the lowest and the highest CPU
frequencies supported by the platform firmware.
The PCC driver loads with a message such as:
pcc-cpufreq: (v1.00.00) driver loaded with frequency limits: 1600 MHz, 2933
MHz
This means that the OPSM can request the CPU to run at any frequency in
between the limits (1600 MHz, and 2933 MHz) specified in the message.
Internally, there is no need for the driver to convert the "target" frequency
to a corresponding P-state.
The VERSION number for the driver will be of the format v.xy.ab.
eg: 1.00.02
----- --
| |
| -- this will increase with bug fixes/enhancements to the driver
|-- this is the version of the PCC specification the driver adheres to
The following is a brief discussion on some of the fields exported via the
/sys filesystem and how their values are affected by the PCC driver:
2.1 scaling_available_frequencies:
----------------------------------
scaling_available_frequencies is not created in /sys. No intermediate
frequencies need to be listed because the BIOS will try to achieve any
frequency, within limits, requested by the governor. A frequency does not have
to be strictly associated with a P-state.
2.2 cpuinfo_transition_latency:
-------------------------------
The cpuinfo_transition_latency field is 0. The PCC specification does
not include a field to expose this value currently.
2.3 cpuinfo_cur_freq:
---------------------
A) Often cpuinfo_cur_freq will show a value different than what is declared
in the scaling_available_frequencies or scaling_cur_freq, or scaling_max_freq.
This is due to "turbo boost" available on recent Intel processors. If certain
conditions are met the BIOS can achieve a slightly higher speed than requested
by OSPM. An example:
scaling_cur_freq : 2933000
cpuinfo_cur_freq : 3196000
B) There is a round-off error associated with the cpuinfo_cur_freq value.
Since the driver obtains the current frequency as a "percentage" (%) of the
nominal frequency from the BIOS, sometimes, the values displayed by
scaling_cur_freq and cpuinfo_cur_freq may not match. An example:
scaling_cur_freq : 1600000
cpuinfo_cur_freq : 1583000
In this example, the nominal frequency is 2933 MHz. The driver obtains the
current frequency, cpuinfo_cur_freq, as 54% of the nominal frequency:
54% of 2933 MHz = 1583 MHz
Nominal frequency is the maximum frequency of the processor, and it usually
corresponds to the frequency of the P0 P-state.
2.4 related_cpus:
-----------------
The related_cpus field is identical to affected_cpus.
affected_cpus : 4
related_cpus : 4
Currently, the PCC driver does not evaluate _PSD. The platforms that support
PCC do not implement SW_ALL. So OSPM doesn't need to perform any coordination
to ensure that the same frequency is requested of all dependent CPUs.
3. Caveats:
-----------
The "cpufreq_stats" module in its present form cannot be loaded and
expected to work with the PCC driver. Since the "cpufreq_stats" module
provides information wrt each P-state, it is not applicable to the PCC driver.

49
Documentation/cpu-hotplug.txt
View file

@ -315,41 +315,26 @@ A: The following are what is required for CPU hotplug infrastructure to work
Q: I need to ensure that a particular cpu is not removed when there is some
work specific to this cpu is in progress.
A: First switch the current thread context to preferred cpu
A: There are two ways. If your code can be run in interrupt context, use
smp_call_function_single(), otherwise use work_on_cpu(). Note that
work_on_cpu() is slow, and can fail due to out of memory:
int my_func_on_cpu(int cpu)
{
cpumask_t saved_mask, new_mask = CPU_MASK_NONE;
int curr_cpu, err = 0;
saved_mask = current->cpus_allowed;
cpu_set(cpu, new_mask);
err = set_cpus_allowed(current, new_mask);
if (err)
return err;
/*
* If we got scheduled out just after the return from
* set_cpus_allowed() before running the work, this ensures
* we stay locked.
*/
curr_cpu = get_cpu();
if (curr_cpu != cpu) {
err = -EAGAIN;
goto ret;
} else {
/*
* Do work : But cant sleep, since get_cpu() disables preempt
*/
}
ret:
put_cpu();
set_cpus_allowed(current, saved_mask);
return err;
}
int err;
get_online_cpus();
if (!cpu_online(cpu))
err = -EINVAL;
else
#if NEEDS_BLOCKING
err = work_on_cpu(cpu, __my_func_on_cpu, NULL);
#else
smp_call_function_single(cpu, __my_func_on_cpu, &err,
true);
#endif
put_online_cpus();
return err;
}
Q: How do we determine how many CPUs are available for hotplug.
A: There is no clear spec defined way from ACPI that can give us that

44
Documentation/device-mapper/snapshot.txt
View file

@ -122,3 +122,47 @@ volumeGroup-base: 0 2097152 snapshot-merge 254:11 254:12 P 16
brw------- 1 root root 254, 11 29 ago 18:15 /dev/mapper/volumeGroup-base-real
brw------- 1 root root 254, 12 29 ago 18:16 /dev/mapper/volumeGroup-base-cow
brw------- 1 root root 254, 10 29 ago 18:16 /dev/mapper/volumeGroup-base
How to determine when a merging is complete
===========================================
The snapshot-merge and snapshot status lines end with:
<sectors_allocated>/<total_sectors> <metadata_sectors>
Both <sectors_allocated> and <total_sectors> include both data and metadata.
During merging, the number of sectors allocated gets smaller and
smaller. Merging has finished when the number of sectors holding data
is zero, in other words <sectors_allocated> == <metadata_sectors>.
Here is a practical example (using a hybrid of lvm and dmsetup commands):
# lvs
LV VG Attr LSize Origin Snap% Move Log Copy% Convert
base volumeGroup owi-a- 4.00g
snap volumeGroup swi-a- 1.00g base 18.97
# dmsetup status volumeGroup-snap
0 8388608 snapshot 397896/2097152 1560
^^^^ metadata sectors
# lvconvert --merge -b volumeGroup/snap
Merging of volume snap started.
# lvs volumeGroup/snap
LV VG Attr LSize Origin Snap% Move Log Copy% Convert
base volumeGroup Owi-a- 4.00g 17.23
# dmsetup status volumeGroup-base
0 8388608 snapshot-merge 281688/2097152 1104
# dmsetup status volumeGroup-base
0 8388608 snapshot-merge 180480/2097152 712
# dmsetup status volumeGroup-base
0 8388608 snapshot-merge 16/2097152 16
Merging has finished.
# lvs
LV VG Attr LSize Origin Snap% Move Log Copy% Convert
base volumeGroup owi-a- 4.00g

2
Documentation/dontdiff
View file

@ -69,7 +69,6 @@ av_permissions.h
bbootsect
bin2c
binkernel.spec
binoffset
bootsect
bounds.h
bsetup
@ -103,6 +102,7 @@ gconf
gen-devlist
gen_crc32table
gen_init_cpio
generated
genheaders
genksyms
*_gray256.c

4
Documentation/driver-model/driver.txt
View file

@ -226,5 +226,5 @@ struct driver_attribute driver_attr_debug;
This can then be used to add and remove the attribute from the
driver's directory using:
int driver_create_file(struct device_driver *, struct driver_attribute *);
void driver_remove_file(struct device_driver *, struct driver_attribute *);
int driver_create_file(struct device_driver *, const struct driver_attribute *);
void driver_remove_file(struct device_driver *, const struct driver_attribute *);

2
Documentation/driver-model/platform.txt
View file

@ -192,7 +192,7 @@ command line. This will execute all matching early_param() callbacks.
User specified early platform devices will be registered at this point.
For the early serial console case the user can specify port on the
kernel command line as "earlyprintk=serial.0" where "earlyprintk" is
the class string, "serial" is the name of the platfrom driver and
the class string, "serial" is the name of the platform driver and
0 is the platform device id. If the id is -1 then the dot and the
id can be omitted.

23
Documentation/dvb/get_dvb_firmware
View file

@ -26,7 +26,7 @@ use IO::Handle;
"dec3000s", "vp7041", "dibusb", "nxt2002", "nxt2004",
"or51211", "or51132_qam", "or51132_vsb", "bluebird",
"opera1", "cx231xx", "cx18", "cx23885", "pvrusb2", "mpc718",
"af9015");
"af9015", "ngene");
# Check args
syntax() if (scalar(@ARGV) != 1);
@ -39,7 +39,7 @@ for ($i=0; $i < scalar(@components); $i++) {
die $@ if $@;
print STDERR <<EOF;
Firmware(s) $outfile extracted successfully.
Now copy it(they) to either /usr/lib/hotplug/firmware or /lib/firmware
Now copy it(them) to either /usr/lib/hotplug/firmware or /lib/firmware
(depending on configuration of firmware hotplug).
EOF
exit(0);
@ -549,6 +549,24 @@ sub af9015 {
close INFILE;
}
sub ngene {
my $url = "http://www.digitaldevices.de/download/";
my $file1 = "ngene_15.fw";
my $hash1 = "d798d5a757121174f0dbc5f2833c0c85";
my $file2 = "ngene_17.fw";
my $hash2 = "26b687136e127b8ac24b81e0eeafc20b";
checkstandard();
wgetfile($file1, $url . $file1);
verify($file1, $hash1);
wgetfile($file2, $url . $file2);
verify($file2, $hash2);
"$file1, $file2";
}
# ---------------------------------------------------------------
# Utilities
@ -667,6 +685,7 @@ sub delzero{
sub syntax() {
print STDERR "syntax: get_dvb_firmware <component>\n";
print STDERR "Supported components:\n";
@components = sort @components;
for($i=0; $i < scalar(@components); $i++) {
print STDERR "\t" . $components[$i] . "\n";
}

2
Documentation/eisa.txt
View file

@ -171,7 +171,7 @@ device.
virtual_root.force_probe :
Force the probing code to probe EISA slots even when it cannot find an
EISA compliant mainboard (nothing appears on slot 0). Defaultd to 0
EISA compliant mainboard (nothing appears on slot 0). Defaults to 0
(don't force), and set to 1 (force probing) when either
CONFIG_ALPHA_JENSEN or CONFIG_EISA_VLB_PRIMING are set.

24
Documentation/email-clients.txt
View file

@ -216,26 +216,14 @@ Works. Use "Insert file..." or external editor.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Gmail (Web GUI)
If you just have to use Gmail to send patches, it CAN be made to work. It
requires a bit of external help, though.
Does not work for sending patches.
The first problem is that Gmail converts tabs to spaces. This will
totally break your patches. To prevent this, you have to use a different
editor. There is a firefox extension called "ViewSourceWith"
(https://addons.mozilla.org/en-US/firefox/addon/394) which allows you to
edit any text box in the editor of your choice. Configure it to launch
your favorite editor. When you want to send a patch, use this technique.
Once you have crafted your messsage + patch, save and exit the editor,
which should reload the Gmail edit box. GMAIL WILL PRESERVE THE TABS.
Hoorah. Apparently you can cut-n-paste literal tabs, but Gmail will
convert those to spaces upon sending!
Gmail web client converts tabs to spaces automatically.
The second problem is that Gmail converts tabs to spaces on replies. If
you reply to a patch, don't expect to be able to apply it as a patch.
At the same time it wraps lines every 78 chars with CRLF style line breaks
although tab2space problem can be solved with external editor.
The last problem is that Gmail will base64-encode any message that has a
non-ASCII character. That includes things like European names. Be aware.
Gmail is not convenient for lkml patches, but CAN be made to work.
Another problem is that Gmail will base64-encode any message that has a
non-ASCII character. That includes things like European names.
###

4
Documentation/fault-injection/fault-injection.txt
View file

@ -143,8 +143,8 @@ o provide a way to configure fault attributes
failslab, fail_page_alloc, and fail_make_request use this way.
Helper functions:
init_fault_attr_entries(entries, attr, name);
void cleanup_fault_attr_entries(entries);
init_fault_attr_dentries(entries, attr, name);
void cleanup_fault_attr_dentries(entries);
- module parameters

38
Documentation/fault-injection/provoke-crashes.txt Normal file
View file

@ -0,0 +1,38 @@
The lkdtm module provides an interface to crash or injure the kernel at
predefined crashpoints to evaluate the reliability of crash dumps obtained
using different dumping solutions. The module uses KPROBEs to instrument
crashing points, but can also crash the kernel directly without KRPOBE
support.
You can provide the way either through module arguments when inserting
the module, or through a debugfs interface.
Usage: insmod lkdtm.ko [recur_count={>0}] cpoint_name=<> cpoint_type=<>
[cpoint_count={>0}]
recur_count : Recursion level for the stack overflow test. Default is 10.
cpoint_name : Crash point where the kernel is to be crashed. It can be
one of INT_HARDWARE_ENTRY, INT_HW_IRQ_EN, INT_TASKLET_ENTRY,
FS_DEVRW, MEM_SWAPOUT, TIMERADD, SCSI_DISPATCH_CMD,
IDE_CORE_CP, DIRECT
cpoint_type : Indicates the action to be taken on hitting the crash point.
It can be one of PANIC, BUG, EXCEPTION, LOOP, OVERFLOW,
CORRUPT_STACK, UNALIGNED_LOAD_STORE_WRITE, OVERWRITE_ALLOCATION,
WRITE_AFTER_FREE,
cpoint_count : Indicates the number of times the crash point is to be hit
to trigger an action. The default is 10.
You can also induce failures by mounting debugfs and writing the type to
<mountpoint>/provoke-crash/<crashpoint>. E.g.,
mount -t debugfs debugfs /mnt
echo EXCEPTION > /mnt/provoke-crash/INT_HARDWARE_ENTRY
A special file is `DIRECT' which will induce the crash directly without
KPROBE instrumentation. This mode is the only one available when the module
is built on a kernel without KPROBEs support.

203
Documentation/feature-removal-schedule.txt
View file

@ -6,21 +6,6 @@ be removed from this file.
---------------------------
What: USER_SCHED
When: 2.6.34
Why: USER_SCHED was implemented as a proof of concept for group scheduling.
The effect of USER_SCHED can already be achieved from userspace with
the help of libcgroup. The removal of USER_SCHED will also simplify
the scheduler code with the removal of one major ifdef. There are also
issues USER_SCHED has with USER_NS. A decision was taken not to fix
those and instead remove USER_SCHED. Also new group scheduling
features will not be implemented for USER_SCHED.
Who: Dhaval Giani <dhaval@linux.vnet.ibm.com>
---------------------------
What: PRISM54
When: 2.6.34
@ -64,6 +49,17 @@ Who: Robin Getz <rgetz@blackfin.uclinux.org> & Matt Mackall <mpm@selenic.com>
---------------------------
What: Deprecated snapshot ioctls
When: 2.6.36
Why: The ioctls in kernel/power/user.c were marked as deprecated long time
ago. Now they notify users about that so that they need to replace
their userspace. After some more time, remove them completely.
Who: Jiri Slaby <jirislaby@gmail.com>
---------------------------
What: The ieee80211_regdom module parameter
When: March 2010 / desktop catchup
@ -88,27 +84,6 @@ Who: Luis R. Rodriguez <lrodriguez@atheros.com>
---------------------------
What: CONFIG_WIRELESS_OLD_REGULATORY - old static regulatory information
When: March 2010 / desktop catchup
Why: The old regulatory infrastructure has been replaced with a new one
which does not require statically defined regulatory domains. We do
not want to keep static regulatory domains in the kernel due to the
the dynamic nature of regulatory law and localization. We kept around
the old static definitions for the regulatory domains of:
* US
* JP
* EU
and used by default the US when CONFIG_WIRELESS_OLD_REGULATORY was
set. We will remove this option once the standard Linux desktop catches
up with the new userspace APIs we have implemented.
Who: Luis R. Rodriguez <lrodriguez@atheros.com>
---------------------------
What: dev->power.power_state
When: July 2007
Why: Broken design for runtime control over driver power states, confusing
@ -142,19 +117,25 @@ Who: Mauro Carvalho Chehab <mchehab@infradead.org>
---------------------------
What: PCMCIA control ioctl (needed for pcmcia-cs [cardmgr, cardctl])
When: November 2005
When: 2.6.35/2.6.36
Files: drivers/pcmcia/: pcmcia_ioctl.c
Why: With the 16-bit PCMCIA subsystem now behaving (almost) like a
normal hotpluggable bus, and with it using the default kernel
infrastructure (hotplug, driver core, sysfs) keeping the PCMCIA
control ioctl needed by cardmgr and cardctl from pcmcia-cs is
unnecessary, and makes further cleanups and integration of the
unnecessary and potentially harmful (it does not provide for
proper locking), and makes further cleanups and integration of the
PCMCIA subsystem into the Linux kernel device driver model more
difficult. The features provided by cardmgr and cardctl are either
handled by the kernel itself now or are available in the new
pcmciautils package available at
http://kernel.org/pub/linux/utils/kernel/pcmcia/
Who: Dominik Brodowski <linux@brodo.de>
For all architectures except ARM, the associated config symbol
has been removed from kernel 2.6.34; for ARM, it will be likely
be removed from kernel 2.6.35. The actual code will then likely
be removed from kernel 2.6.36.
Who: Dominik Brodowski <linux@dominikbrodowski.net>
---------------------------
@ -468,9 +449,143 @@ Who: Alok N Kataria <akataria@vmware.com>
----------------------------
What: adt7473 hardware monitoring driver
When: February 2010
Why: Obsoleted by the adt7475 driver.
Who: Jean Delvare <khali@linux-fr.org>
What: Support for lcd_switch and display_get in asus-laptop driver
When: March 2010
Why: These two features use non-standard interfaces. There are the
only features that really need multiple path to guess what's
the right method name on a specific laptop.
---------------------------
Removing them will allow to remove a lot of code an significantly
clean the drivers.
This will affect the backlight code which won't be able to know
if the backlight is on or off. The platform display file will also be
write only (like the one in eeepc-laptop).
This should'nt affect a lot of user because they usually know
when their display is on or off.
Who: Corentin Chary <corentin.chary@gmail.com>
----------------------------
What: usbvideo quickcam_messenger driver
When: 2.6.35
Files: drivers/media/video/usbvideo/quickcam_messenger.[ch]
Why: obsolete v4l1 driver replaced by gspca_stv06xx
Who: Hans de Goede <hdegoede@redhat.com>
----------------------------
What: ov511 v4l1 driver
When: 2.6.35
Files: drivers/media/video/ov511.[ch]
Why: obsolete v4l1 driver replaced by gspca_ov519
Who: Hans de Goede <hdegoede@redhat.com>
----------------------------
What: w9968cf v4l1 driver
When: 2.6.35
Files: drivers/media/video/w9968cf*.[ch]
Why: obsolete v4l1 driver replaced by gspca_ov519
Who: Hans de Goede <hdegoede@redhat.com>
----------------------------
What: ovcamchip sensor framework
When: 2.6.35
Files: drivers/media/video/ovcamchip/*
Why: Only used by obsoleted v4l1 drivers
Who: Hans de Goede <hdegoede@redhat.com>
----------------------------
What: stv680 v4l1 driver
When: 2.6.35
Files: drivers/media/video/stv680.[ch]
Why: obsolete v4l1 driver replaced by gspca_stv0680
Who: Hans de Goede <hdegoede@redhat.com>
----------------------------
What: zc0301 v4l driver
When: 2.6.35
Files: drivers/media/video/zc0301/*
Why: Duplicate functionality with the gspca_zc3xx driver, zc0301 only
supports 2 USB-ID's (because it only supports a limited set of
sensors) wich are also supported by the gspca_zc3xx driver
(which supports 53 USB-ID's in total)
Who: Hans de Goede <hdegoede@redhat.com>
----------------------------
What: corgikbd, spitzkbd, tosakbd driver
When: 2.6.35
Files: drivers/input/keyboard/{corgi,spitz,tosa}kbd.c
Why: We now have a generic GPIO based matrix keyboard driver that
are fully capable of handling all the keys on these devices.
The original drivers manipulate the GPIO registers directly
and so are difficult to maintain.
Who: Eric Miao <eric.y.miao@gmail.com>
----------------------------
What: corgi_ssp and corgi_ts driver
When: 2.6.35
Files: arch/arm/mach-pxa/corgi_ssp.c, drivers/input/touchscreen/corgi_ts.c
Why: The corgi touchscreen is now deprecated in favour of the generic
ads7846.c driver. The noise reduction technique used in corgi_ts.c,
that's to wait till vsync before ADC sampling, is also integrated into
ads7846 driver now. Provided that the original driver is not generic
and is difficult to maintain, it will be removed later.
Who: Eric Miao <eric.y.miao@gmail.com>
----------------------------
What: capifs
When: February 2011
Files: drivers/isdn/capi/capifs.*
Why: udev fully replaces this special file system that only contains CAPI
NCCI TTY device nodes. User space (pppdcapiplugin) works without
noticing the difference.
Who: Jan Kiszka <jan.kiszka@web.de>
----------------------------
What: KVM memory aliases support
When: July 2010
Why: Memory aliasing support is used for speeding up guest vga access
through the vga windows.
Modern userspace no longer uses this feature, so it's just bitrotted
code and can be removed with no impact.
Who: Avi Kivity <avi@redhat.com>
----------------------------
What: KVM kernel-allocated memory slots
When: July 2010
Why: Since 2.6.25, kvm supports user-allocated memory slots, which are
much more flexible than kernel-allocated slots. All current userspace
supports the newer interface and this code can be removed with no
impact.
Who: Avi Kivity <avi@redhat.com>
----------------------------
What: KVM paravirt mmu host support
When: January 2011
Why: The paravirt mmu host support is slower than non-paravirt mmu, both
on newer and older hardware. It is already not exposed to the guest,
and kept only for live migration purposes.
Who: Avi Kivity <avi@redhat.com>
----------------------------
What: "acpi=ht" boot option
When: 2.6.35
Why: Useful in 2003, implementation is a hack.
Generally invoked by accident today.
Seen as doing more harm than good.
Who: Len Brown <len.brown@intel.com>

18
Documentation/filesystems/00-INDEX
View file

@ -1,7 +1,5 @@
00-INDEX
- this file (info on some of the filesystems supported by linux).
Exporting
- explanation of how to make filesystems exportable.
Locking
- info on locking rules as they pertain to Linux VFS.
9p.txt
@ -18,6 +16,8 @@ befs.txt
- information about the BeOS filesystem for Linux.
bfs.txt
- info for the SCO UnixWare Boot Filesystem (BFS).
ceph.txt
- info for the Ceph Distributed File System
cifs.txt
- description of the CIFS filesystem.
coda.txt
@ -34,6 +34,8 @@ dlmfs.txt
- info on the userspace interface to the OCFS2 DLM.
dnotify.txt
- info about directory notification in Linux.
dnotify_test.c
- example program for dnotify
ecryptfs.txt
- docs on eCryptfs: stacked cryptographic filesystem for Linux.
exofs.txt
@ -64,16 +66,14 @@ jfs.txt
- info and mount options for the JFS filesystem.
locks.txt
- info on file locking implementations, flock() vs. fcntl(), etc.
logfs.txt
- info on the LogFS flash filesystem.
mandatory-locking.txt
- info on the Linux implementation of Sys V mandatory file locking.
ncpfs.txt
- info on Novell Netware(tm) filesystem using NCP protocol.
nfs41-server.txt
- info on the Linux server implementation of NFSv4 minor version 1.
nfs-rdma.txt
- how to install and setup the Linux NFS/RDMA client and server software.
nfsroot.txt
- short guide on setting up a diskless box with NFS root filesystem.
nfs/
- nfs-related documentation.
nilfs2.txt
- info and mount options for the NILFS2 filesystem.
ntfs.txt
@ -92,8 +92,6 @@ relay.txt
- info on relay, for efficient streaming from kernel to user space.
romfs.txt
- description of the ROMFS filesystem.
rpc-cache.txt
- introduction to the caching mechanisms in the sunrpc layer.
seq_file.txt
- how to use the seq_file API
sharedsubtree.txt

18
Documentation/filesystems/Locking
View file

@ -460,13 +460,6 @@ in sys_read() and friends.
--------------------------- dquot_operations -------------------------------
prototypes:
int (*initialize) (struct inode *, int);
int (*drop) (struct inode *);
int (*alloc_space) (struct inode *, qsize_t, int);
int (*alloc_inode) (const struct inode *, unsigned long);
int (*free_space) (struct inode *, qsize_t);
int (*free_inode) (const struct inode *, unsigned long);
int (*transfer) (struct inode *, struct iattr *);
int (*write_dquot) (struct dquot *);
int (*acquire_dquot) (struct dquot *);
int (*release_dquot) (struct dquot *);
@ -479,13 +472,6 @@ a proper locking wrt the filesystem and call the generic quota operations.
What filesystem should expect from the generic quota functions:
FS recursion Held locks when called
initialize: yes maybe dqonoff_sem
drop: yes -
alloc_space: ->mark_dirty() -
alloc_inode: ->mark_dirty() -
free_space: ->mark_dirty() -
free_inode: ->mark_dirty() -
transfer: yes -
write_dquot: yes dqonoff_sem or dqptr_sem
acquire_dquot: yes dqonoff_sem or dqptr_sem
release_dquot: yes dqonoff_sem or dqptr_sem
@ -495,10 +481,6 @@ write_info: yes dqonoff_sem
FS recursion means calling ->quota_read() and ->quota_write() from superblock
operations.
->alloc_space(), ->alloc_inode(), ->free_space(), ->free_inode() are called
only directly by the filesystem and do not call any fs functions only
the ->mark_dirty() operation.
More details about quota locking can be found in fs/dquot.c.
--------------------------- vm_operations_struct -----------------------------

8
Documentation/filesystems/Makefile Normal file
View file

@ -0,0 +1,8 @@
# kbuild trick to avoid linker error. Can be omitted if a module is built.
obj- := dummy.o
# List of programs to build
hostprogs-y := dnotify_test
# Tell kbuild to always build the programs
always := $(hostprogs-y)

140
Documentation/filesystems/ceph.txt Normal file
View file

@ -0,0 +1,140 @@
Ceph Distributed File System
============================
Ceph is a distributed network file system designed to provide good
performance, reliability, and scalability.
Basic features include:
* POSIX semantics
* Seamless scaling from 1 to many thousands of nodes
* High availability and reliability. No single point of failure.
* N-way replication of data across storage nodes
* Fast recovery from node failures
* Automatic rebalancing of data on node addition/removal
* Easy deployment: most FS components are userspace daemons
Also,
* Flexible snapshots (on any directory)
* Recursive accounting (nested files, directories, bytes)
In contrast to cluster filesystems like GFS, OCFS2, and GPFS that rely
on symmetric access by all clients to shared block devices, Ceph
separates data and metadata management into independent server
clusters, similar to Lustre. Unlike Lustre, however, metadata and
storage nodes run entirely as user space daemons. Storage nodes
utilize btrfs to store data objects, leveraging its advanced features
(checksumming, metadata replication, etc.). File data is striped
across storage nodes in large chunks to distribute workload and
facilitate high throughputs. When storage nodes fail, data is
re-replicated in a distributed fashion by the storage nodes themselves
(with some minimal coordination from a cluster monitor), making the
system extremely efficient and scalable.
Metadata servers effectively form a large, consistent, distributed
in-memory cache above the file namespace that is extremely scalable,
dynamically redistributes metadata in response to workload changes,
and can tolerate arbitrary (well, non-Byzantine) node failures. The
metadata server takes a somewhat unconventional approach to metadata
storage to significantly improve performance for common workloads. In
particular, inodes with only a single link are embedded in
directories, allowing entire directories of dentries and inodes to be
loaded into its cache with a single I/O operation. The contents of
extremely large directories can be fragmented and managed by
independent metadata servers, allowing scalable concurrent access.
The system offers automatic data rebalancing/migration when scaling
from a small cluster of just a few nodes to many hundreds, without
requiring an administrator carve the data set into static volumes or
go through the tedious process of migrating data between servers.
When the file system approaches full, new nodes can be easily added
and things will "just work."
Ceph includes flexible snapshot mechanism that allows a user to create
a snapshot on any subdirectory (and its nested contents) in the
system. Snapshot creation and deletion are as simple as 'mkdir
.snap/foo' and 'rmdir .snap/foo'.
Ceph also provides some recursive accounting on directories for nested
files and bytes. That is, a 'getfattr -d foo' on any directory in the
system will reveal the total number of nested regular files and
subdirectories, and a summation of all nested file sizes. This makes
the identification of large disk space consumers relatively quick, as
no 'du' or similar recursive scan of the file system is required.
Mount Syntax
============
The basic mount syntax is:
# mount -t ceph monip[:port][,monip2[:port]...]:/[subdir] mnt
You only need to specify a single monitor, as the client will get the
full list when it connects. (However, if the monitor you specify
happens to be down, the mount won't succeed.) The port can be left
off if the monitor is using the default. So if the monitor is at
1.2.3.4,
# mount -t ceph 1.2.3.4:/ /mnt/ceph
is sufficient. If /sbin/mount.ceph is installed, a hostname can be
used instead of an IP address.
Mount Options
=============
ip=A.B.C.D[:N]
Specify the IP and/or port the client should bind to locally.
There is normally not much reason to do this. If the IP is not
specified, the client's IP address is determined by looking at the
address it's connection to the monitor originates from.
wsize=X
Specify the maximum write size in bytes. By default there is no
maximum. Ceph will normally size writes based on the file stripe
size.
rsize=X
Specify the maximum readahead.
mount_timeout=X
Specify the timeout value for mount (in seconds), in the case
of a non-responsive Ceph file system. The default is 30
seconds.
rbytes
When stat() is called on a directory, set st_size to 'rbytes',
the summation of file sizes over all files nested beneath that
directory. This is the default.
norbytes
When stat() is called on a directory, set st_size to the
number of entries in that directory.
nocrc
Disable CRC32C calculation for data writes. If set, the storage node
must rely on TCP's error correction to detect data corruption
in the data payload.
noasyncreaddir
Disable client's use its local cache to satisfy readdir
requests. (This does not change correctness; the client uses
cached metadata only when a lease or capability ensures it is
valid.)
More Information
================
For more information on Ceph, see the home page at
http://ceph.newdream.net/
The Linux kernel client source tree is available at
git://ceph.newdream.net/git/ceph-client.git
git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client.git
and the source for the full system is at
git://ceph.newdream.net/git/ceph.git

3
Documentation/filesystems/dentry-locking.txt
View file

@ -62,7 +62,8 @@ changes are :
2. Insertion of a dentry into the hash table is done using
hlist_add_head_rcu() which take care of ordering the writes - the
writes to the dentry must be visible before the dentry is
inserted. This works in conjunction with hlist_for_each_rcu() while
inserted. This works in conjunction with hlist_for_each_rcu(),
which has since been replaced by hlist_for_each_entry_rcu(), while
walking the hash chain. The only requirement is that all
initialization to the dentry must be done before
hlist_add_head_rcu() since we don't have dcache_lock protection

39
Documentation/filesystems/dnotify.txt
View file

@ -62,38 +62,9 @@ disabled, fcntl(fd, F_NOTIFY, ...) will return -EINVAL.
Example
-------
See Documentation/filesystems/dnotify_test.c for an example.
#define _GNU_SOURCE /* needed to get the defines */
#include <fcntl.h> /* in glibc 2.2 this has the needed
values defined */
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
static volatile int event_fd;
static void handler(int sig, siginfo_t *si, void *data)
{
event_fd = si->si_fd;
}
int main(void)
{
struct sigaction act;
int fd;
act.sa_sigaction = handler;
sigemptyset(&act.sa_mask);
act.sa_flags = SA_SIGINFO;
sigaction(SIGRTMIN + 1, &act, NULL);
fd = open(".", O_RDONLY);
fcntl(fd, F_SETSIG, SIGRTMIN + 1);
fcntl(fd, F_NOTIFY, DN_MODIFY|DN_CREATE|DN_MULTISHOT);
/* we will now be notified if any of the files
in "." is modified or new files are created */
while (1) {
pause();
printf("Got event on fd=%d\n", event_fd);
}
}
NOTE
----
Beginning with Linux 2.6.13, dnotify has been replaced by inotify.
See Documentation/filesystems/inotify.txt for more information on it.

34
Documentation/filesystems/dnotify_test.c Normal file
View file

@ -0,0 +1,34 @@
#define _GNU_SOURCE /* needed to get the defines */
#include <fcntl.h> /* in glibc 2.2 this has the needed
values defined */
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
static volatile int event_fd;
static void handler(int sig, siginfo_t *si, void *data)
{
event_fd = si->si_fd;
}
int main(void)
{
struct sigaction act;
int fd;
act.sa_sigaction = handler;
sigemptyset(&act.sa_mask);
act.sa_flags = SA_SIGINFO;
sigaction(SIGRTMIN + 1, &act, NULL);
fd = open(".", O_RDONLY);
fcntl(fd, F_SETSIG, SIGRTMIN + 1);
fcntl(fd, F_NOTIFY, DN_MODIFY|DN_CREATE|DN_MULTISHOT);
/* we will now be notified if any of the files
in "." is modified or new files are created */
while (1) {
pause();
printf("Got event on fd=%d\n", event_fd);
}
}

2
Documentation/filesystems/ext4.txt
View file

@ -196,7 +196,7 @@ nobarrier This also requires an IO stack which can support
also be used to enable or disable barriers, for
consistency with other ext4 mount options.
inode_readahead=n This tuning parameter controls the maximum
inode_readahead_blks=n This tuning parameter controls the maximum
number of inode table blocks that ext4's inode
table readahead algorithm will pre-read into
the buffer cache. The default value is 32 blocks.

241
Documentation/filesystems/logfs.txt Normal file
View file

@ -0,0 +1,241 @@
The LogFS Flash Filesystem
==========================
Specification
=============
Superblocks
-----------
Two superblocks exist at the beginning and end of the filesystem.
Each superblock is 256 Bytes large, with another 3840 Bytes reserved
for future purposes, making a total of 4096 Bytes.
Superblock locations may differ for MTD and block devices. On MTD the
first non-bad block contains a superblock in the first 4096 Bytes and
the last non-bad block contains a superblock in the last 4096 Bytes.
On block devices, the first 4096 Bytes of the device contain the first
superblock and the last aligned 4096 Byte-block contains the second
superblock.
For the most part, the superblocks can be considered read-only. They
are written only to correct errors detected within the superblocks,
move the journal and change the filesystem parameters through tunefs.
As a result, the superblock does not contain any fields that require
constant updates, like the amount of free space, etc.
Segments
--------
The space in the device is split up into equal-sized segments.
Segments are the primary write unit of LogFS. Within each segments,
writes happen from front (low addresses) to back (high addresses. If
only a partial segment has been written, the segment number, the
current position within and optionally a write buffer are stored in
the journal.
Segments are erased as a whole. Therefore Garbage Collection may be
required to completely free a segment before doing so.
Journal
--------
The journal contains all global information about the filesystem that
is subject to frequent change. At mount time, it has to be scanned
for the most recent commit entry, which contains a list of pointers to
all currently valid entries.
Object Store
------------
All space except for the superblocks and journal is part of the object
store. Each segment contains a segment header and a number of
objects, each consisting of the object header and the payload.
Objects are either inodes, directory entries (dentries), file data
blocks or indirect blocks.
Levels
------
Garbage collection (GC) may fail if all data is written
indiscriminately. One requirement of GC is that data is seperated
roughly according to the distance between the tree root and the data.
Effectively that means all file data is on level 0, indirect blocks
are on levels 1, 2, 3 4 or 5 for 1x, 2x, 3x, 4x or 5x indirect blocks,
respectively. Inode file data is on level 6 for the inodes and 7-11
for indirect blocks.
Each segment contains objects of a single level only. As a result,
each level requires its own seperate segment to be open for writing.
Inode File
----------
All inodes are stored in a special file, the inode file. Single
exception is the inode file's inode (master inode) which for obvious
reasons is stored in the journal instead. Instead of data blocks, the
leaf nodes of the inode files are inodes.
Aliases
-------
Writes in LogFS are done by means of a wandering tree. A naïve
implementation would require that for each write or a block, all
parent blocks are written as well, since the block pointers have
changed. Such an implementation would not be very efficient.
In LogFS, the block pointer changes are cached in the journal by means
of alias entries. Each alias consists of its logical address - inode
number, block index, level and child number (index into block) - and
the changed data. Any 8-byte word can be changes in this manner.
Currently aliases are used for block pointers, file size, file used
bytes and the height of an inodes indirect tree.
Segment Aliases
---------------
Related to regular aliases, these are used to handle bad blocks.
Initially, bad blocks are handled by moving the affected segment
content to a spare segment and noting this move in the journal with a
segment alias, a simple (to, from) tupel. GC will later empty this
segment and the alias can be removed again. This is used on MTD only.
Vim
---
By cleverly predicting the life time of data, it is possible to
seperate long-living data from short-living data and thereby reduce
the GC overhead later. Each type of distinc life expectency (vim) can
have a seperate segment open for writing. Each (level, vim) tupel can
be open just once. If an open segment with unknown vim is encountered
at mount time, it is closed and ignored henceforth.
Indirect Tree
-------------
Inodes in LogFS are similar to FFS-style filesystems with direct and
indirect block pointers. One difference is that LogFS uses a single
indirect pointer that can be either a 1x, 2x, etc. indirect pointer.
A height field in the inode defines the height of the indirect tree
and thereby the indirection of the pointer.
Another difference is the addressing of indirect blocks. In LogFS,
the first 16 pointers in the first indirect block are left empty,
corresponding to the 16 direct pointers in the inode. In ext2 (maybe
others as well) the first pointer in the first indirect block
corresponds to logical block 12, skipping the 12 direct pointers.
So where ext2 is using arithmetic to better utilize space, LogFS keeps
arithmetic simple and uses compression to save space.
Compression
-----------
Both file data and metadata can be compressed. Compression for file
data can be enabled with chattr +c and disabled with chattr -c. Doing
so has no effect on existing data, but new data will be stored
accordingly. New inodes will inherit the compression flag of the
parent directory.
Metadata is always compressed. However, the space accounting ignores
this and charges for the uncompressed size. Failing to do so could
result in GC failures when, after moving some data, indirect blocks
compress worse than previously. Even on a 100% full medium, GC may
not consume any extra space, so the compression gains are lost space
to the user.
However, they are not lost space to the filesystem internals. By
cheating the user for those bytes, the filesystem gained some slack
space and GC will run less often and faster.
Garbage Collection and Wear Leveling
------------------------------------
Garbage collection is invoked whenever the number of free segments
falls below a threshold. The best (known) candidate is picked based
on the least amount of valid data contained in the segment. All
remaining valid data is copied elsewhere, thereby invalidating it.
The GC code also checks for aliases and writes then back if their
number gets too large.
Wear leveling is done by occasionally picking a suboptimal segment for
garbage collection. If a stale segments erase count is significantly
lower than the active segments' erase counts, it will be picked. Wear
leveling is rate limited, so it will never monopolize the device for
more than one segment worth at a time.
Values for "occasionally", "significantly lower" are compile time
constants.
Hashed directories
------------------
To satisfy efficient lookup(), directory entries are hashed and
located based on the hash. In order to both support large directories
and not be overly inefficient for small directories, several hash
tables of increasing size are used. For each table, the hash value
modulo the table size gives the table index.
Tables sizes are chosen to limit the number of indirect blocks with a
fully populated table to 0, 1, 2 or 3 respectively. So the first
table contains 16 entries, the second 512-16, etc.
The last table is special in several ways. First its size depends on
the effective 32bit limit on telldir/seekdir cookies. Since logfs
uses the upper half of the address space for indirect blocks, the size
is limited to 2^31. Secondly the table contains hash buckets with 16
entries each.
Using single-entry buckets would result in birthday "attacks". At
just 2^16 used entries, hash collisions would be likely (P >= 0.5).
My math skills are insufficient to do the combinatorics for the 17x
collisions necessary to overflow a bucket, but testing showed that in
10,000 runs the lowest directory fill before a bucket overflow was
188,057,130 entries with an average of 315,149,915 entries. So for
directory sizes of up to a million, bucket overflows should be
virtually impossible under normal circumstances.
With carefully chosen filenames, it is obviously possible to cause an
overflow with just 21 entries (4 higher tables + 16 entries + 1). So
there may be a security concern if a malicious user has write access
to a directory.
Open For Discussion
===================
Device Address Space
--------------------
A device address space is used for caching. Both block devices and
MTD provide functions to either read a single page or write a segment.
Partial segments may be written for data integrity, but where possible
complete segments are written for performance on simple block device
flash media.
Meta Inodes
-----------
Inodes are stored in the inode file, which is just a regular file for
most purposes. At umount time, however, the inode file needs to
remain open until all dirty inodes are written. So
generic_shutdown_super() may not close this inode, but shouldn't
complain about remaining inodes due to the inode file either. Same
goes for mapping inode of the device address space.
Currently logfs uses a hack that essentially copies part of fs/inode.c
code over. A general solution would be preferred.
Indirect block mapping
----------------------
With compression, the block device (or mapping inode) cannot be used
to cache indirect blocks. Some other place is required. Currently
logfs uses the top half of each inode's address space. The low 8TB
(on 32bit) are filled with file data, the high 8TB are used for
indirect blocks.
One problem is that 16TB files created on 64bit systems actually have
data in the top 8TB. But files >16TB would cause problems anyway, so
only the limit has changed.

16
Documentation/filesystems/nfs/00-INDEX Normal file
View file

@ -0,0 +1,16 @@
00-INDEX
- this file (nfs-related documentation).
Exporting
- explanation of how to make filesystems exportable.
knfsd-stats.txt
- statistics which the NFS server makes available to user space.
nfs.txt
- nfs client, and DNS resolution for fs_locations.
nfs41-server.txt
- info on the Linux server implementation of NFSv4 minor version 1.
nfs-rdma.txt
- how to install and setup the Linux NFS/RDMA client and server software
nfsroot.txt
- short guide on setting up a diskless box with NFS root filesystem.
rpc-cache.txt
- introduction to the caching mechanisms in the sunrpc layer.

0
Documentation/filesystems/Exporting → Documentation/filesystems/nfs/Exporting
View file

0
Documentation/filesystems/knfsd-stats.txt → Documentation/filesystems/nfs/knfsd-stats.txt
View file

0
Documentation/filesystems/nfs-rdma.txt → Documentation/filesystems/nfs/nfs-rdma.txt
View file

0
Documentation/filesystems/nfs.txt → Documentation/filesystems/nfs/nfs.txt
View file

14
Documentation/filesystems/nfs41-server.txt → Documentation/filesystems/nfs/nfs41-server.txt
View file

@ -17,8 +17,7 @@ kernels must turn 4.1 on or off *before* turning support for version 4
on or off; rpc.nfsd does this correctly.)
The NFSv4 minorversion 1 (NFSv4.1) implementation in nfsd is based
on the latest NFSv4.1 Internet Draft:
http://tools.ietf.org/html/draft-ietf-nfsv4-minorversion1-29
on RFC 5661.
From the many new features in NFSv4.1 the current implementation
focuses on the mandatory-to-implement NFSv4.1 Sessions, providing
@ -41,10 +40,10 @@ interoperability problems with future clients. Known issues:
conformant with the spec (for example, we don't use kerberos
on the backchannel correctly).
- no trunking support: no clients currently take advantage of
trunking, but this is a mandatory failure, and its use is
trunking, but this is a mandatory feature, and its use is
recommended to clients in a number of places. (E.g. to ensure
timely renewal in case an existing connection's retry timeouts
have gotten too long; see section 8.3 of the draft.)
have gotten too long; see section 8.3 of the RFC.)
Therefore, lack of this feature may cause future clients to
fail.
- Incomplete backchannel support: incomplete backchannel gss
@ -213,3 +212,10 @@ The following cases aren't supported yet:
DESTROY_CLIENTID, DESTROY_SESSION, EXCHANGE_ID.
* DESTROY_SESSION MUST be the final operation in the COMPOUND request.
Nonstandard compound limitations:
* No support for a sessions fore channel RPC compound that requires both a
ca_maxrequestsize request and a ca_maxresponsesize reply, so we may
fail to live up to the promise we made in CREATE_SESSION fore channel
negotiation.
* No more than one IO operation (read, write, readdir) allowed per
compound.

0
Documentation/filesystems/nfsroot.txt → Documentation/filesystems/nfs/nfsroot.txt
View file

0
Documentation/filesystems/rpc-cache.txt → Documentation/filesystems/nfs/rpc-cache.txt
View file

5
Documentation/filesystems/nilfs2.txt
View file

@ -28,7 +28,7 @@ described in the man pages included in the package.
Project web page: http://www.nilfs.org/en/
Download page: http://www.nilfs.org/en/download.html
Git tree web page: http://www.nilfs.org/git/
NILFS mailing lists: http://www.nilfs.org/mailman/listinfo/users
List info: http://vger.kernel.org/vger-lists.html#linux-nilfs
Caveats
=======
@ -74,6 +74,9 @@ norecovery Disable recovery of the filesystem on mount.
This disables every write access on the device for
read-only mounts or snapshots. This option will fail
for r/w mounts on an unclean volume.
discard Issue discard/TRIM commands to the underlying block
device when blocks are freed. This is useful for SSD
devices and sparse/thinly-provisioned LUNs.
NILFS2 usage
============

2
Documentation/filesystems/porting
View file

@ -140,7 +140,7 @@ Callers of notify_change() need ->i_mutex now.
New super_block field "struct export_operations *s_export_op" for
explicit support for exporting, e.g. via NFS. The structure is fully
documented at its declaration in include/linux/fs.h, and in
Documentation/filesystems/Exporting.
Documentation/filesystems/nfs/Exporting.
Briefly it allows for the definition of decode_fh and encode_fh operations
to encode and decode filehandles, and allows the filesystem to use

57
Documentation/filesystems/proc.txt
View file

@ -164,6 +164,7 @@ read the file /proc/PID/status:
VmExe: 68 kB
VmLib: 1412 kB
VmPTE: 20 kb
VmSwap: 0 kB
Threads: 1
SigQ: 0/28578
SigPnd: 0000000000000000
@ -177,7 +178,6 @@ read the file /proc/PID/status:
CapBnd: ffffffffffffffff
voluntary_ctxt_switches: 0
nonvoluntary_ctxt_switches: 1
Stack usage: 12 kB
This shows you nearly the same information you would get if you viewed it with
the ps command. In fact, ps uses the proc file system to obtain its
@ -189,7 +189,13 @@ memory usage. Its seven fields are explained in Table 1-3. The stat file
contains details information about the process itself. Its fields are
explained in Table 1-4.
Table 1-2: Contents of the statm files (as of 2.6.30-rc7)
(for SMP CONFIG users)
For making accounting scalable, RSS related information are handled in
asynchronous manner and the vaule may not be very precise. To see a precise
snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
It's slow but very precise.
Table 1-2: Contents of the status files (as of 2.6.30-rc7)
..............................................................................
Field Content
Name filename of the executable
@ -214,6 +220,7 @@ Table 1-2: Contents of the statm files (as of 2.6.30-rc7)
VmExe size of text segment
VmLib size of shared library code
VmPTE size of page table entries
VmSwap size of swap usage (the number of referred swapents)
Threads number of threads
SigQ number of signals queued/max. number for queue
SigPnd bitmap of pending signals for the thread
@ -231,7 +238,6 @@ Table 1-2: Contents of the statm files (as of 2.6.30-rc7)
Mems_allowed_list Same as previous, but in "list format"
voluntary_ctxt_switches number of voluntary context switches
nonvoluntary_ctxt_switches number of non voluntary context switches
Stack usage: stack usage high water mark (round up to page size)
..............................................................................
Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
@ -432,6 +438,7 @@ Table 1-5: Kernel info in /proc
modules List of loaded modules
mounts Mounted filesystems
net Networking info (see text)
pagetypeinfo Additional page allocator information (see text) (2.5)
partitions Table of partitions known to the system
pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
decoupled by lspci (2.4)
@ -586,7 +593,7 @@ Node 0, zone DMA 0 4 5 4 4 3 ...
Node 0, zone Normal 1 0 0 1 101 8 ...
Node 0, zone HighMem 2 0 0 1 1 0 ...
Memory fragmentation is a problem under some workloads, and buddyinfo is a
External fragmentation is a problem under some workloads, and buddyinfo is a
useful tool for helping diagnose these problems. Buddyinfo will give you a
clue as to how big an area you can safely allocate, or why a previous
allocation failed.
@ -596,6 +603,48 @@ available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
available in ZONE_NORMAL, etc...
More information relevant to external fragmentation can be found in
pagetypeinfo.
> cat /proc/pagetypeinfo
Page block order: 9
Pages per block: 512
Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
Node 0, zone DMA 2 0 5 1 0
Node 0, zone DMA32 41 6 967 2 0
Fragmentation avoidance in the kernel works by grouping pages of different
migrate types into the same contiguous regions of memory called page blocks.
A page block is typically the size of the default hugepage size e.g. 2MB on
X86-64. By keeping pages grouped based on their ability to move, the kernel
can reclaim pages within a page block to satisfy a high-order allocation.
The pagetypinfo begins with information on the size of a page block. It
then gives the same type of information as buddyinfo except broken down
by migrate-type and finishes with details on how many page blocks of each
type exist.
If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
make an estimate of the likely number of huge pages that can be allocated
at a given point in time. All the "Movable" blocks should be allocatable
unless memory has been mlock()'d. Some of the Reclaimable blocks should
also be allocatable although a lot of filesystem metadata may have to be
reclaimed to achieve this.
..............................................................................
meminfo:

16
Documentation/filesystems/sharedsubtree.txt
View file

@ -837,6 +837,9 @@ replicas continue to be exactly same.
individual lists does not affect propagation or the way propagation
tree is modified by operations.
All vfsmounts in a peer group have the same ->mnt_master. If it is
non-NULL, they form a contiguous (ordered) segment of slave list.
A example propagation tree looks as shown in the figure below.
[ NOTE: Though it looks like a forest, if we consider all the shared
mounts as a conceptual entity called 'pnode', it becomes a tree]
@ -874,8 +877,19 @@ replicas continue to be exactly same.
NOTE: The propagation tree is orthogonal to the mount tree.
8B Locking:
8B Algorithm:
->mnt_share, ->mnt_slave, ->mnt_slave_list, ->mnt_master are protected
by namespace_sem (exclusive for modifications, shared for reading).
Normally we have ->mnt_flags modifications serialized by vfsmount_lock.
There are two exceptions: do_add_mount() and clone_mnt().
The former modifies a vfsmount that has not been visible in any shared
data structures yet.
The latter holds namespace_sem and the only references to vfsmount
are in lists that can't be traversed without namespace_sem.
8C Algorithm:
The crux of the implementation resides in rbind/move operation.

12
Documentation/filesystems/sysfs.txt
View file

@ -91,8 +91,8 @@ struct device_attribute {
const char *buf, size_t count);
};
int device_create_file(struct device *, struct device_attribute *);
void device_remove_file(struct device *, struct device_attribute *);
int device_create_file(struct device *, const struct device_attribute *);
void device_remove_file(struct device *, const struct device_attribute *);
It also defines this helper for defining device attributes:
@ -316,8 +316,8 @@ DEVICE_ATTR(_name, _mode, _show, _store);
Creation/Removal:
int device_create_file(struct device *device, struct device_attribute * attr);
void device_remove_file(struct device * dev, struct device_attribute * attr);
int device_create_file(struct device *dev, const struct device_attribute * attr);
void device_remove_file(struct device *dev, const struct device_attribute * attr);
- bus drivers (include/linux/device.h)
@ -358,7 +358,7 @@ DRIVER_ATTR(_name, _mode, _show, _store)
Creation/Removal:
int driver_create_file(struct device_driver *, struct driver_attribute *);
void driver_remove_file(struct device_driver *, struct driver_attribute *);
int driver_create_file(struct device_driver *, const struct driver_attribute *);
void driver_remove_file(struct device_driver *, const struct driver_attribute *);

6
Documentation/filesystems/tmpfs.txt
View file

@ -82,11 +82,13 @@ tmpfs has a mount option to set the NUMA memory allocation policy for
all files in that instance (if CONFIG_NUMA is enabled) - which can be
adjusted on the fly via 'mount -o remount ...'
mpol=default prefers to allocate memory from the local node
mpol=default use the process allocation policy
(see set_mempolicy(2))
mpol=prefer:Node prefers to allocate memory from the given Node
mpol=bind:NodeList allocates memory only from nodes in NodeList
mpol=interleave prefers to allocate from each node in turn
mpol=interleave:NodeList allocates from each node of NodeList in turn
mpol=local prefers to allocate memory from the local node
NodeList format is a comma-separated list of decimal numbers and ranges,
a range being two hyphen-separated decimal numbers, the smallest and
@ -134,3 +136,5 @@ Author:
Christoph Rohland <cr@sap.com>, 1.12.01
Updated:
Hugh Dickins, 4 June 2007
Updated:
KOSAKI Motohiro, 16 Mar 2010

64
Documentation/gpio.txt
View file

@ -253,6 +253,70 @@ pin setup (e.g. controlling which pin the GPIO uses, pullup/pulldown).
Also note that it's your responsibility to have stopped using a GPIO
before you free it.
Considering in most cases GPIOs are actually configured right after they
are claimed, three additional calls are defined:
/* request a single GPIO, with initial configuration specified by
* 'flags', identical to gpio_request() wrt other arguments and
* return value
*/
int gpio_request_one(unsigned gpio, unsigned long flags, const char *label);
/* request multiple GPIOs in a single call
*/
int gpio_request_array(struct gpio *array, size_t num);
/* release multiple GPIOs in a single call
*/
void gpio_free_array(struct gpio *array, size_t num);
where 'flags' is currently defined to specify the following properties:
* GPIOF_DIR_IN - to configure direction as input
* GPIOF_DIR_OUT - to configure direction as output
* GPIOF_INIT_LOW - as output, set initial level to LOW
* GPIOF_INIT_HIGH - as output, set initial level to HIGH
since GPIOF_INIT_* are only valid when configured as output, so group valid
combinations as:
* GPIOF_IN - configure as input
* GPIOF_OUT_INIT_LOW - configured as output, initial level LOW
* GPIOF_OUT_INIT_HIGH - configured as output, initial level HIGH
In the future, these flags can be extended to support more properties such
as open-drain status.
Further more, to ease the claim/release of multiple GPIOs, 'struct gpio' is
introduced to encapsulate all three fields as:
struct gpio {
unsigned gpio;
unsigned long flags;
const char *label;
};
A typical example of usage:
static struct gpio leds_gpios[] = {
{ 32, GPIOF_OUT_INIT_HIGH, "Power LED" }, /* default to ON */
{ 33, GPIOF_OUT_INIT_LOW, "Green LED" }, /* default to OFF */
{ 34, GPIOF_OUT_INIT_LOW, "Red LED" }, /* default to OFF */
{ 35, GPIOF_OUT_INIT_LOW, "Blue LED" }, /* default to OFF */
{ ... },
};
err = gpio_request_one(31, GPIOF_IN, "Reset Button");
if (err)
...
err = gpio_request_array(leds_gpios, ARRAY_SIZE(leds_gpios));
if (err)
...
gpio_free_array(leds_gpios, ARRAY_SIZE(leds_gpios));
GPIOs mapped to IRQs
--------------------

2
Documentation/hwmon/abituguru
View file

@ -30,7 +30,7 @@ Supported chips:
bank1_types=1,1,0,0,0,0,0,2,0,0,0,0,2,0,0,1
You may also need to specify the fan_sensors option for these boards
fan_sensors=5
2) There is a seperate abituguru3 driver for these motherboards,
2) There is a separate abituguru3 driver for these motherboards,
the abituguru (without the 3 !) driver will not work on these
motherboards (and visa versa)!

42
Documentation/hwmon/adt7411 Normal file
View file

@ -0,0 +1,42 @@
Kernel driver adt7411
=====================
Supported chips:
* Analog Devices ADT7411
Prefix: 'adt7411'
Addresses scanned: 0x48, 0x4a, 0x4b
Datasheet: Publicly available at the Analog Devices website
Author: Wolfram Sang (based on adt7470 by Darrick J. Wong)
Description
-----------
This driver implements support for the Analog Devices ADT7411 chip. There may
be other chips that implement this interface.
The ADT7411 can use an I2C/SMBus compatible 2-wire interface or an
SPI-compatible 4-wire interface. It provides a 10-bit analog to digital
converter which measures 1 temperature, vdd and 8 input voltages. It has an
internal temperature sensor, but an external one can also be connected (one
loses 2 inputs then). There are high- and low-limit registers for all inputs.
Check the datasheet for details.
sysfs-Interface
---------------
in0_input - vdd voltage input
in[1-8]_input - analog 1-8 input
temp1_input - temperature input
Besides standard interfaces, this driver adds (0 = off, 1 = on):
adc_ref_vdd - Use vdd as reference instead of 2.25 V
fast_sampling - Sample at 22.5 kHz instead of 1.4 kHz, but drop filters
no_average - Turn off averaging over 16 samples
Notes
-----
SPI, external temperature sensor and limit registers are not supported yet.

74
Documentation/hwmon/adt7473
View file

@ -1,74 +0,0 @@
Kernel driver adt7473
======================
Supported chips:
* Analog Devices ADT7473
Prefix: 'adt7473'
Addresses scanned: I2C 0x2C, 0x2D, 0x2E
Datasheet: Publicly available at the Analog Devices website
Author: Darrick J. Wong
This driver is depreacted, please use the adt7475 driver instead.
Description
-----------
This driver implements support for the Analog Devices ADT7473 chip family.
The ADT7473 uses the 2-wire interface compatible with the SMBUS 2.0
specification. Using an analog to digital converter it measures three (3)
temperatures and two (2) voltages. It has four (4) 16-bit counters for
measuring fan speed. There are three (3) PWM outputs that can be used
to control fan speed.
A sophisticated control system for the PWM outputs is designed into the
ADT7473 that allows fan speed to be adjusted automatically based on any of the
three temperature sensors. Each PWM output is individually adjustable and
programmable. Once configured, the ADT7473 will adjust the PWM outputs in
response to the measured temperatures without further host intervention.
This feature can also be disabled for manual control of the PWM's.
Each of the measured inputs (voltage, temperature, fan speed) has
corresponding high/low limit values. The ADT7473 will signal an ALARM if
any measured value exceeds either limit.
The ADT7473 samples all inputs continuously. The driver will not read
the registers more often than once every other second. Further,
configuration data is only read once per minute.
Special Features
----------------
The ADT7473 have a 10-bit ADC and can therefore measure temperatures
with 0.25 degC resolution. Temperature readings can be configured either
for twos complement format or "Offset 64" format, wherein 63 is subtracted
from the raw value to get the temperature value.
The Analog Devices datasheet is very detailed and describes a procedure for
determining an optimal configuration for the automatic PWM control.
Configuration Notes
-------------------
Besides standard interfaces driver adds the following:
* PWM Control
* pwm#_auto_point1_pwm and temp#_auto_point1_temp and
* pwm#_auto_point2_pwm and temp#_auto_point2_temp -
point1: Set the pwm speed at a lower temperature bound.
point2: Set the pwm speed at a higher temperature bound.
The ADT7473 will scale the pwm between the lower and higher pwm speed when
the temperature is between the two temperature boundaries. PWM values range
from 0 (off) to 255 (full speed). Fan speed will be set to maximum when the
temperature sensor associated with the PWM control exceeds temp#_max.
Notes
-----
The NVIDIA binary driver presents an ADT7473 chip via an on-card i2c bus.
Unfortunately, they fail to set the i2c adapter class, so this driver may
fail to find the chip until the nvidia driver is patched.

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Kernel driver amc6821
=====================
Supported chips:
Texas Instruments AMC6821
Prefix: 'amc6821'
Addresses scanned: 0x18, 0x19, 0x1a, 0x2c, 0x2d, 0x2e, 0x4c, 0x4d, 0x4e
Datasheet: http://focus.ti.com/docs/prod/folders/print/amc6821.html
Authors:
Tomaz Mertelj <tomaz.mertelj@guest.arnes.si>
Description
-----------
This driver implements support for the Texas Instruments amc6821 chip.
The chip has one on-chip and one remote temperature sensor and one pwm fan
regulator.
The pwm can be controlled either from software or automatically.
The driver provides the following sensor accesses in sysfs:
temp1_input ro on-chip temperature
temp1_min rw "
temp1_max rw "
temp1_crit rw "
temp1_min_alarm ro "
temp1_max_alarm ro "
temp1_crit_alarm ro "
temp2_input ro remote temperature
temp2_min rw "
temp2_max rw "
temp2_crit rw "
temp2_min_alarm ro "
temp2_max_alarm ro "
temp2_crit_alarm ro "
temp2_fault ro "
fan1_input ro tachometer speed
fan1_min rw "
fan1_max rw "
fan1_fault ro "
fan1_div rw Fan divisor can be either 2 or 4.
pwm1 rw pwm1
pwm1_enable rw regulator mode, 1=open loop, 2=fan controlled
by remote temperature, 3=fan controlled by
combination of the on-chip temperature and
remote-sensor temperature,
pwm1_auto_channels_temp ro 1 if pwm_enable==2, 3 if pwm_enable==3
pwm1_auto_point1_pwm ro Hardwired to 0, shared for both
temperature channels.
pwm1_auto_point2_pwm rw This value is shared for both temperature
channels.
pwm1_auto_point3_pwm rw Hardwired to 255, shared for both
temperature channels.
temp1_auto_point1_temp ro Hardwired to temp2_auto_point1_temp
which is rw. Below this temperature fan stops.
temp1_auto_point2_temp rw The low-temperature limit of the proportional
range. Below this temperature
pwm1 = pwm1_auto_point2_pwm. It can go from
0 degree C to 124 degree C in steps of
4 degree C. Read it out after writing to get
the actual value.
temp1_auto_point3_temp rw Above this temperature fan runs at maximum
speed. It can go from temp1_auto_point2_temp.
It can only have certain discrete values
which depend on temp1_auto_point2_temp and
pwm1_auto_point2_pwm. Read it out after
writing to get the actual value.
temp2_auto_point1_temp rw Must be between 0 degree C and 63 degree C and
it defines the passive cooling temperature.
Below this temperature the fan stops in
the closed loop mode.
temp2_auto_point2_temp rw The low-temperature limit of the proportional
range. Below this temperature
pwm1 = pwm1_auto_point2_pwm. It can go from
0 degree C to 124 degree C in steps
of 4 degree C.
temp2_auto_point3_temp rw Above this temperature fan runs at maximum
speed. It can only have certain discrete
values which depend on temp2_auto_point2_temp
and pwm1_auto_point2_pwm. Read it out after
writing to get actual value.
Module parameters
-----------------
If your board has a BIOS that initializes the amc6821 correctly, you should
load the module with: init=0.
If your board BIOS doesn't initialize the chip, or you want
different settings, you can set the following parameters:
init=1,
pwminv: 0 default pwm output, 1 inverts pwm output.

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