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Takashi Iwai ab949d5196 ALSA: hda - Fix deadlock of controller device lock at unbinding
Imre Deak reported a deadlock of HD-audio driver at unbinding while
it's still in probing.  Since we probe the codecs asynchronously in a
work, the codec driver probe may still be kicked off while the
controller itself is being unbound.  And, azx_remove() tries to
process all pending tasks via cancel_work_sync() for fixing the other
races (see commit [0b8c82190c: ALSA: hda - Cancel probe work instead
of flush at remove]), now we may meet a bizarre deadlock:

Unbind snd_hda_intel via sysfs:
  device_release_driver() ->
    device_lock(snd_hda_intel) ->
      azx_remove() ->
        cancel_work_sync(azx_probe_work)

azx_probe_work():
  codec driver probe() ->
     __driver_attach() ->
       device_lock(snd_hda_intel)

This deadlock is caused by the fact that both device_release_driver()
and driver_probe_device() take both the device and its parent locks at
the same time.  The codec device sets the controller device as its
parent, and this lock is taken before the probe() callback is called,
while the controller remove() callback gets called also with the same
lock.

In this patch, as an ugly workaround, we unlock the controller device
temporarily during cancel_work_sync() call.  The race against another
bind call should be still suppressed by the parent's device lock.

Reported-by: Imre Deak <imre.deak@intel.com>
Fixes: 0b8c82190c ("ALSA: hda - Cancel probe work instead of flush at remove")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2017-01-04 11:22:55 +01:00
arch mm: optimize PageWaiters bit use for unlock_page() 2016-12-29 11:03:15 -08:00
block ktime: Cleanup ktime_set() usage 2016-12-25 17:21:22 +01:00
certs certs: Add a secondary system keyring that can be added to dynamically 2016-04-11 22:48:09 +01:00
crypto crypto: testmgr - Use heap buffer for acomp test input 2016-12-27 17:32:11 +08:00
Documentation Documentation/unaligned-memory-access.txt: fix incorrect comparison operator 2016-12-27 13:08:42 -07:00
drivers Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2016-12-27 17:51:36 -08:00
firmware WHENCE: use https://linuxtv.org for LinuxTV URLs 2015-12-04 10:35:11 -02:00
fs ext4: Simplify DAX fault path 2016-12-26 20:29:25 -08:00
include Merge branch 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm 2017-01-01 12:27:05 -08:00
init mm: add PageWaiters indicating tasks are waiting for a page bit 2016-12-25 11:54:48 -08:00
ipc ipc/sem: avoid idr tree lookup for interrupted semop 2016-12-14 16:04:08 -08:00
kernel smp/hotplug: Undo tglxs brainfart 2016-12-26 17:30:24 -08:00
lib Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-12-25 14:30:04 -08:00
mm Merge branch 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm 2017-01-01 12:27:05 -08:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-12-27 16:04:37 -08:00
samples Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-12-23 16:49:12 -08:00
scripts Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2016-12-22 10:03:52 -08:00
security Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
sound ALSA: hda - Fix deadlock of controller device lock at unbinding 2017-01-04 11:22:55 +01:00
tools Merge branch 'turbostat' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux 2016-12-25 14:01:28 -08:00
usr initramfs: allow again choice of the embedded initram compression algorithm 2016-12-14 16:04:08 -08:00
virt Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-12-25 14:30:04 -08:00
.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 Merge branch 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild 2016-08-02 16:48:52 -04:00
.mailmap Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2016-10-15 09:26:12 -07:00
COPYING
CREDITS CREDITS: Remove outdated address information 2016-12-21 15:21:29 -08:00
Kbuild scripts/gdb: provide linux constants 2016-05-23 17:04:14 -07:00
Kconfig kbuild: migrate all arch to the kconfig mainmenu upgrade 2010-09-19 22:54:11 -04:00
MAINTAINERS Watchdog updates for v4.10 2016-12-24 11:27:45 -08:00
Makefile Linux 4.10-rc2 2017-01-01 14:31:53 -08:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

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.