Don't update dev->power.power_state any more in the SPI core. The only
reason to update this scheduled-to-be-removed field was to make the
already-removed /sys/devices/.../power/state files work better.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit edfaa7c365
Driver core: convert block from raw kobjects to core devices
This moves the block devices to /sys/class/block. It will create a
flat list of all block devices, with the disks and partitions in one
directory. For compatibility /sys/block is created and contains symlinks
to the disks.
introduced a global disk_type variable in <linux/genhd.h>, causing the
following compile error on Atari:
drivers/block/ataflop.c:93: error: conflicting types for 'disk_type'
include/linux/genhd.h:21: error: previous declaration of 'disk_type' was here
Rename the local disk_type variable in drivers/block/ataflop.c to
atari_disk_type, to avoid the conflict.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Standardize the temperature units to millidegrees C for the two sensor
conversion routines. Previously the routines were,
w1_DS18B20_convert_temp degrees C
w1_DS18S20_convert_temp millidegrees C
Unfortunately this will break any program using the ds18b20 value as it
will now be 1000 times bigger. Fortunately there can't be that many users
out there, or some of these bugs will have been fixed by now, such as the
negative C error (see previous patch) that makes me think the ds18b20 is
the better choice to change because of the current bugs.
Signed-off-by: David Fries <david@fries.net>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Remvoe variable which actually is not used (except assigning it a value)
and confusing break out of the family checking loop. Found by Harry Mason.
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Cc: Harry J Mason <hjm03r@ecs.soton.ac.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix section mismatch by making the driver template variable name
match one of the whitelisted variable names in modpost.
WARNING: vmlinux.o(.data+0x7a9e8): Section mismatch: reference to .init.text:tpm_inf_pnp_probe (between 'tpm_inf_pnp' and 'cn_idx')
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Marcel Selhorst <tpm@selhorst.net>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The kernel has a divide by zero crash when trying to run the system timer
less than 100Hz. The problem is x/(HZ/USER_HZ) and related. Now
x*(USER_HZ/HZ) will be used if HZ<USER_HZ.
I'm running the Linux kernel under qemu and went to run a slower system
timer to take less CPU (and battery) on the host. I found that the kernel
paniced under emulation because of a divide by zero in three places. Here
is the patch. The base git was updated today 01-05-2008. I went for a
20Hz system time by adding config HZ_20 etc to kernel/Kconfig.hz. With
this patch I verified the system timer by looking at /proc/interrupts.
[akpm@linux-foundation.org: partially clean up the macro maze]
Signed-off-by: David Fries <david@fries.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Specify also sub pci ids to not grab devices with properly set sub ids.
This devices has these set (unset) to the same as (plx 9050) ids.
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Andreas Block <andreas.block@esd-electronics.com>
Cc: Oliver Thimm <oliver.thimm@esd-electronics.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I have been prime author and maintainer of block2mtd from day one, but
neither MAINTAINERS nor the module source makes this fact clear. And while
I'm at it, update my email addresses tree-wide, as the old address
currently bounces and change my name to "joern" as unicode will likely
continue to cause trouble until the end of this century.
Signed-off-by: Joern Engel <joern@lazybastard.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Here's a couple of small additions to BUG-HUNTING.
1. point out that you can list code in gdb with only one command
(gdb) l *(<symbol> + offset)
2. give a very brief hint how to decode module symbols in call traces
Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
schedule_timeout(jiffies) waits for at least jiffies - 1. Add 1 jiffie to
the timeout_jiffies calculated in sys_poll() to wait at least
timeout_msecs, like poll() manpage says.
Signed-off-by: Karsten Wiese <fzu@wemgehoertderstaat.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix two N_TTY line discipline issues related to resuming a stopped TTY
(typically done with ctrl-S):
1) Fix handling of character that resumes a stopped TTY (with IXANY)
With "stty ixany", the TTY line discipline would lose the first character
after the stop, so typing, for example, "hi^Sthere" resulted in "hihere"
(the 't' would cause the resume after ^S, but it would then be thrown away
rather than processed as an input character). This was inconsistent with
the behavior of other Unix systems.
2) Fix interrupt signal (e.g. ctrl-C) behavior in stopped TTYs
With "stty -ixany" (often the default), interrupt signals were ignored
in a stopped TTY until the TTY was resumed with the start char (typically
ctrl-Q), which was inconsistent with the behavior of other Unix systems.
Signed-off-by: Joe Peterson <joe@skyrush.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Just converting this documentation semaphore reference, since we don't
want to promote semaphore usage.
Signed-off-by: Daniel Walker <dwalker@mvista.com>
Acked-by: Corey Minyard <minyard@acm.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We can use ilog2() in fs/namespace.c to compute hash_bits and hash_mask at
compile time, not runtime.
[akpm@linux-foundation.org: clean it all up]
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- Account for debug_smp_processor_id()'s own preempt_disable() when
displaying the preempt_count().
- 80 cols, not 800.
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
groups_sort() can be quite long if user loads a large gid table.
This is because GROUP_AT(group_info, some_integer) uses an integer divide.
So having to do XXX thousand divides during one syscall can lead to very
high latencies. (NGROUPS_MAX=65536)
In the past (25 Mar 2006), an analog problem was found in groups_search()
(commit d74beb9f33 ) and at that time I
changed some variables to unsigned int.
I believe that a more generic fix is to make sure NGROUPS_PER_BLOCK is
unsigned.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
calibrate_delay() must be __cpuinit, not __{dev,}init.
I've verified that this is correct for all users.
While doing the latter, I also did the following cleanups:
- remove pointless additional prototypes in C files
- ensure all users #include <linux/delay.h>
This fixes the following section mismatches with CONFIG_HOTPLUG=n,
CONFIG_HOTPLUG_CPU=y:
WARNING: vmlinux.o(.text+0x1128d): Section mismatch: reference to .init.text.1:calibrate_delay (between 'check_cx686_slop' and 'set_cx86_reorder')
WARNING: vmlinux.o(.text+0x25102): Section mismatch: reference to .init.text.1:calibrate_delay (between 'smp_callin' and 'cpu_coregroup_map')
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Richard Henderson <rth@twiddle.net>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Christian Zankel <chris@zankel.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add detection for IT87XX SuperIO chip and disabling its POST feature, which
made noise on parallel port's pins.
Signed-off-by: Petr Cvek <petr.cvek@tul.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add the Dell UK 6400 Inspiron model (MM061) to allow the i8k module to load
correctly without using 'force=1'
Signed-off-by: "Nick Warne" <nick@ukfsn.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use DEFAULT_SGI_PARTITION for SGI_PARTION default
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix wrong netmos 9855 serial port configuration.
On loading only one serial port was present and it wasn't working. After
looking in the data sheet I realized that the base address was wrong. For
further reference here is lspci and relevant dmesg output:
02:00.0 Communication controller: NetMos Technology PCI 9855 Multi-I/O
Controller (rev 01) (prog-if 02)
Subsystem: LSI Logic / Symbios Logic Unknown device 0022
Flags: medium devsel, IRQ 19
I/O ports at df00 [size=8]
I/O ports at de00 [size=8]
I/O ports at dd00 [size=8]
I/O ports at dc00 [size=8]
I/O ports at db00 [size=8]
I/O ports at da00 [size=16]
parport1: PC-style at 0xdd00 [PCSPP,TRISTATE]
parport2: PC-style at 0xdf00 [PCSPP,TRISTATE,EPP]
0000:02:00.0: ttyS0 at I/O 0xdb00 (irq = 19) is a 16550A
0000:02:00.0: ttyS1 at I/O 0xda00 (irq = 19) is a 16550A
Signed-off-by: Christian Pellegrin <chripell@fsfe.org>
Cc: Thomas Richter <thor@math.TU-Berlin.DE>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Martin Schitter <ms@gewi.kfunigraz.ac.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Added pci device id for the Quatech SPPXP-100 ExpressCard - 0x278 - to
include/linux/pci_id.h
Modified drivers/parport/parport_pc.c to support the Quatech SPPXP-100 Parallel port PCI ExpressCard
[akpm@linux-foundation.org: build fix]
Signed-off-by: Luís P Mendes <luis.p.mendes@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
ext2 should not worry about checking sb->s_blocksize for XIP before the
sb's blocksize actually gets set.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The port_write_mutex was converted from a semaphore to a mutex,
but there was still this ifdef'd init_MUTEX reference remaining.
Signed-off-by: Daniel Walker <dwalker@mvista.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I converted some of the document to reflect mutex usage instead of
semaphore usage. Since we shouldin't be promoting semaphore usage when
it's on it's way out..
Signed-off-by: Daniel Walker <dwalker@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Turn on INTR/QUIT/SUSP echoing in the N_TTY line discipline (e.g. ctrl-C
will appear as "^C" if stty echoctl is set and ctrl-C is set as INTR).
Linux seems to be the only unix-like OS (recently I've verified this on
Solaris, BSD, and Mac OS X) that does *not* behave this way, and I really
miss this as a good visual confirmation of the interrupt of a program in
the console or xterm. I remember this fondly from many Unixs I've used
over the years as well. Bringing this to Linux also seems like a good way
to make it yet more compliant with standard unix-like behavior.
[akpm@linux-foundation.org: coding-style fixes]
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This adds support to allow asm/ptrace.h to define two new macros,
arch_ptrace_stop_needed and arch_ptrace_stop. These control special
machine-specific actions to be done before a ptrace stop. The new code
compiles away to nothing when the new macros are not defined. This is the
case on all machines to begin with.
On ia64, these macros will be defined to solve the long-standing issue of
ptrace vs register backing store.
Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Petr Tesarik <ptesarik@suse.cz>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Matthew Wilcox <willy@debian.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We restarted scan of sb->s_inodes list whenever we had to drop inode_lock
in add_dquot_ref(). This leads to overall quadratic running time and thus
add_dquot_ref() can take several minutes when called on a life filesystem.
We fix the problem by using the fact that inode cannot be removed from
s_inodes list while we hold a reference to it and thus we can safely
restart the scan if we don't drop the reference. Here we use the fact that
inodes freshly added to s_inodes list are already guaranteed to have quotas
properly initialized and the ordering of inodes on s_inodes list does not
change so we cannot skip any inode.
Thanks goes to Nick <gentuu@gmail.com> for analyzing the problem and
testing the fix.
[akpm@linux-foundation.org: iput(NULL) is legal]
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Nick <gentuu@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
single list_head variable initialized with LIST_HEAD_INIT could almost
always can be replaced with LIST_HEAD declaration, this shrinks the code
and looks better.
Signed-off-by: Denis Cheng <crquan@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Corey Minyard <minyard@acm.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Convert uio from nopage to fault.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Hans J Koch <hjk@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Convert relay from nopage to fault.
Remove redundant vma range checks.
Switch from OOM to SIGBUS if the resource is not available.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Tom Zanussi <zanussi@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When resolving symbol names from addresses with aliased symbol names,
kallsyms_lookup always returns the first symbol, even if it is a weak
symbol.
This patch changes this by sorting the symbols with the weak symbols last
before feeding them to the kernel. This way the kernel runtime isn't
changed at all, only the kallsyms build system is changed.
Another side effect is that the symbols get sorted by address, too. So,
even if future binutils version have some bug in "nm" that makes it fail to
correctly sort symbols by address, the kernel won't be affected by this.
Mathieu says:
I created a module in LTTng that uses kallsyms to get the symbol
corresponding to a specific system call address. Unfortunately, all the
unimplemented syscalls were all referring to the (same) weak symbol
identifying an unrelated system call rather that sys_ni (or whatever
non-weak symbol would be expected). Kallsyms was dumbly returning the first
symbol that matched.
This patch makes sure kallsyms returns the non-weak symbol when there is
one, which seems to be the expected result.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Looks-great-to: Rusty Russell <rusty@rustcorp.com.au>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Convert the unix98 allocated_ptys_lock to a mutex.
Signed-off-by: Daniel Walker <dwalker@mvista.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I couldn't find any users, so removing it..
Signed-off-by: Daniel Walker <dwalker@mvista.com>
Cc: Karsten Keil <kkeil@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I couldn't find any users, so removing it..
Signed-off-by: Daniel Walker <dwalker@mvista.com>
Acked-by: Alan Cox <alan@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Here's a document I wrote after figuring out what unaligned memory access
is all about. I've tried to cover the information I was looking for when
trying to learn about this, without producing a hopelessly detailed/complex
spew. I hope it is useful to others.
Signed-off-by: Daniel Drake <dsd@gentoo.org>
Cc: Rob Landley <rob@landley.net>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Jan Engelhardt <jengelh@computergmbh.de>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Kyle Moffett <mrmacman_g4@mac.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The inotify debugging code is supposed to verify that the
DCACHE_INOTIFY_PARENT_WATCHED scalability optimisation does not result in
notifications getting lost nor extra needless locking generated.
Unfortunately there are also some races in the debugging code. And it isn't
very good at finding problems anyway. So remove it for now.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Robert Love <rlove@google.com>
Cc: John McCutchan <ttb@tentacle.dhs.org>
Cc: Jan Kara <jack@ucw.cz>
Cc: Yan Zheng <yanzheng@21cn.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is a race between setting an inode's children's "parent watched" flag
when placing the first watch on a parent, and instantiating new children of
that parent: a child could miss having its flags set by
set_dentry_child_flags, but then inotify_d_instantiate might still see
!inotify_inode_watched.
The solution is to set_dentry_child_flags after adding the watch. Locking is
taken care of, because both set_dentry_child_flags and inotify_d_instantiate
hold dcache_lock and child->d_locks.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Robert Love <rlove@google.com>
Cc: John McCutchan <ttb@tentacle.dhs.org>
Cc: Jan Kara <jack@ucw.cz>
Cc: Yan Zheng <yanzheng@21cn.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
New serial driver for SC2681/SC2691 uarts. Older SNI RM400 machines are
using these chips for onboard serial ports.
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Torben Mathiasen <device@lanana.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- Use SGI_HAS_ZILOG for IP22_ZILOG depends
- remove IP22 from description, because the driver works on more than
IP22 SGI machines
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Given that init/Makefile includes initramfs.c in the build only if
CONFIG_BLK_DEV_INITRD is defined, there seems to be no point checking for
it yet again.
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The rcu_assign_pointer() primitive currently unconditionally executes a
memory barrier, even when a NULL pointer is being assigned. This has lead
some to avoid using rcu_assign_pointer() for NULL pointers, which loses the
self-documenting advantages of rcu_assign_pointer() This patch uses
__builtin_const_p() to omit needless memory barriers for NULL-pointer
assignments at compile time with no runtime penalty, as discussed in the
following thread:
http://www.mail-archive.com/netdev@vger.kernel.org/msg54852.html
Tested on x86_64 and ppc64, also compiled the four cases (NULL/non-NULL
and const/non-const) with gcc version 4.1.2, and hand-checked the
assembly output.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
David Brownell