redonkable/remarkable-linux
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Hans de Goede 75fb636324 drm: Fix oops + Xserver hang when unplugging USB drm devices 
commit a39be606f9 ("drm: Do a full device unregister when unplugging")
causes backtraces like this one when unplugging an usb drm device while
it is in use:

usb 2-3: USB disconnect, device number 25
------------[ cut here ]------------
WARNING: CPU: 0 PID: 242 at drivers/gpu/drm/drm_mode_config.c:424
   drm_mode_config_cleanup+0x220/0x280 [drm]
...
RIP: 0010:drm_mode_config_cleanup+0x220/0x280 [drm]
...
Call Trace:
 gm12u320_modeset_cleanup+0xe/0x10 [gm12u320]
 gm12u320_driver_unload+0x35/0x70 [gm12u320]
 drm_dev_unregister+0x3c/0xe0 [drm]
 drm_unplug_dev+0x12/0x60 [drm]
 gm12u320_usb_disconnect+0x36/0x40 [gm12u320]
 usb_unbind_interface+0x72/0x280
 device_release_driver_internal+0x158/0x210
 device_release_driver+0x12/0x20
 bus_remove_device+0x104/0x180
 device_del+0x1d2/0x350
 usb_disable_device+0x9f/0x270
 usb_disconnect+0xc6/0x260
...
[drm:drm_mode_config_cleanup [drm]] *ERROR* connector Unknown-1 leaked!
------------[ cut here ]------------
WARNING: CPU: 0 PID: 242 at drivers/gpu/drm/drm_mode_config.c:458
   drm_mode_config_cleanup+0x268/0x280 [drm]
...
<same Call Trace>
---[ end trace 80df975dae439ed6 ]---
general protection fault: 0000 [#1] SMP
...
Call Trace:
 ? __switch_to+0x225/0x450
 drm_mode_rmfb_work_fn+0x55/0x70 [drm]
 process_one_work+0x193/0x3c0
 worker_thread+0x4a/0x3a0
...
RIP: drm_framebuffer_remove+0x62/0x3f0 [drm] RSP: ffffb776c39dfd98
---[ end trace 80df975dae439ed7 ]---

After which the system is unusable this is caused by drm_dev_unregister
getting called immediately on unplug, which calls the drivers unload
function which calls drm_mode_config_cleanup which removes the framebuffer
object while userspace is still holding a reference to it.

Reverting commit a39be606f9 ("drm: Do a full device unregister
when unplugging") leads to the following oops on unplug instead,
when userspace closes the last fd referencing the drm_dev:

sysfs group 'power' not found for kobject 'card1-Unknown-1'
------------[ cut here ]------------
WARNING: CPU: 0 PID: 2459 at fs/sysfs/group.c:237
   sysfs_remove_group+0x80/0x90
...
RIP: 0010:sysfs_remove_group+0x80/0x90
...
Call Trace:
 dpm_sysfs_remove+0x57/0x60
 device_del+0xfd/0x350
 device_unregister+0x1a/0x60
 drm_sysfs_connector_remove+0x39/0x50 [drm]
 drm_connector_unregister+0x5a/0x70 [drm]
 drm_connector_unregister_all+0x45/0xa0 [drm]
 drm_modeset_unregister_all+0x12/0x30 [drm]
 drm_dev_unregister+0xca/0xe0 [drm]
 drm_put_dev+0x32/0x60 [drm]
 drm_release+0x2f3/0x380 [drm]
 __fput+0xdf/0x1e0
...
---[ end trace ecfb91ac85688bbe ]---
BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8
IP: down_write+0x1f/0x40
...
Call Trace:
 debugfs_remove_recursive+0x55/0x1b0
 drm_debugfs_connector_remove+0x21/0x40 [drm]
 drm_connector_unregister+0x62/0x70 [drm]
 drm_connector_unregister_all+0x45/0xa0 [drm]
 drm_modeset_unregister_all+0x12/0x30 [drm]
 drm_dev_unregister+0xca/0xe0 [drm]
 drm_put_dev+0x32/0x60 [drm]
 drm_release+0x2f3/0x380 [drm]
 __fput+0xdf/0x1e0
...
---[ end trace ecfb91ac85688bbf ]---

This is caused by the revert moving back to drm_unplug_dev calling
drm_minor_unregister which does:

        device_del(minor->kdev);
        dev_set_drvdata(minor->kdev, NULL); /* safety belt */
        drm_debugfs_cleanup(minor);

Causing the sysfs entries to already be removed even though we still
have references to them in e.g. drm_connector.

Note we must call drm_minor_unregister to notify userspace of the unplug
of the device, so calling drm_dev_unregister is not completely wrong the
problem is that drm_dev_unregister does too much.

This commit fixes drm_unplug_dev by not only reverting
commit a39be606f9 ("drm: Do a full device unregister when unplugging")
but by also adding a call to drm_modeset_unregister_all before the
drm_minor_unregister calls to make sure all sysfs entries are removed
before calling device_del(minor->kdev) thereby also fixing the second
set of oopses caused by just reverting the commit.

Fixes: a39be606f9 ("drm: Do a full device unregister when unplugging")
Cc: stable@vger.kernel.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jeffy <jeffy.chen@rock-chips.com>
Cc: Marco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>
Reported-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170601115430.4113-1-hdegoede@redhat.com
2017-06-02 11:09:35 -04:00
arch x86: fix 32-bit case of __get_user_asm_u64() 2017-05-21 18:26:54 -07:00
block Merge branch 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm 2017-05-12 15:43:10 -07:00
certs scripts/spelling.txt: add "intialise(d)" pattern and fix typo instances 2017-05-08 17:15:13 -07:00
crypto treewide: use kv[mz]alloc* rather than opencoded variants 2017-05-08 17:15:13 -07:00
Documentation Staging driver fixes for 4.12-rc2 2017-05-20 09:02:27 -07:00
drivers drm: Fix oops + Xserver hang when unplugging USB drm devices 2017-06-02 11:09:35 -04:00
firmware firmware/Makefile: force recompilation if makefile changes 2017-05-08 17:15:10 -07:00
fs Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2017-05-20 16:12:30 -07:00
include This fixes a bug caused by not cleaning up the new instance unique triggers 2017-05-20 23:39:03 -07:00
init Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-05-10 10:30:46 -07:00
ipc mm: introduce kv[mz]alloc helpers 2017-05-08 17:15:12 -07:00
kernel Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-05-21 11:52:00 -07:00
lib dmaengine updates for 4.12-rc1 2017-05-09 15:40:28 -07:00
mm mm: vmscan: scan until it finds eligible pages 2017-05-12 15:57:16 -07:00
net xen: fixes for 4.12 rc2 2017-05-19 15:06:48 -07:00
samples samples/bpf: run cleanup routines when receiving SIGTERM 2017-05-11 21:43:30 -04:00
scripts DeviceTree fixes for 4.12-rc: 2017-05-19 15:03:24 -07:00
security Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-05-09 09:12:53 -07:00
sound drm/i915: Fix runtime PM for LPE audio 2017-05-15 14:44:11 +03:00
tools This fixes a bug caused by not cleaning up the new instance unique triggers 2017-05-20 23:39:03 -07:00
usr initramfs: provide a way to ignore image provided by bootloader 2017-05-08 17:15:12 -07:00
virt KVM: arm/arm64: Hold slots_lock when unregistering kvm io bus devices 2017-05-18 11:18:16 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support to generate LLVM assembly files 2017-04-25 08:13:52 +09:00
.mailmap power supply and reset changes for the v4.12 series (part 2) 2017-05-12 12:02:21 -07:00
COPYING
CREDITS avr32: remove support for AVR32 architecture 2017-05-01 09:27:15 +02:00
Kbuild kbuild: Consolidate header generation from ASM offset information 2017-04-13 05:43:37 +09:00
Kconfig kbuild: migrate all arch to the kconfig mainmenu upgrade 2010-09-19 22:54:11 -04:00
MAINTAINERS Staging driver fixes for 4.12-rc2 2017-05-20 09:02:27 -07:00
Makefile Linux 4.12-rc2 2017-05-21 19:30:23 -07:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.