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033919e0f8
linux/drivers/media
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Heiner Kallweit 033919e0f8 [media] media: rc: fix deadlock when module ir_lirc_codec is removed 
When removing module ir_lirc_codec I got this deadlock warning.
Fix this by introducing a separate mutex to protect access
to available_protocols instead of using ir_raw_handler_lock
for this purpose.

======================================================
[ INFO: possible circular locking dependency detected ]
4.7.0-next-20160729 #1 Not tainted
-------------------------------------------------------
rmmod/2542 is trying to acquire lock:
 (&dev->lock){+.+.+.}, at: [<ffffffffa03b1267>]
			ir_raw_handler_unregister+0x77/0xd0 [rc_core]

but task is already holding lock:
 (ir_raw_handler_lock){+.+.+.}, at: [<ffffffffa03b1212>]
			ir_raw_handler_unregister+0x22/0xd0 [rc_core]

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (ir_raw_handler_lock){+.+.+.}:
       [<ffffffff810ab1f2>] lock_acquire+0xb2/0x1e0
       [<ffffffff815c087f>] mutex_lock_nested+0x5f/0x360
       [<ffffffffa03b1403>] ir_raw_get_allowed_protocols+0x13/0x30 [rc_core]
       [<ffffffffa03af8ea>] store_protocols+0x2fa/0x480 [rc_core]
       [<ffffffff8143e143>] dev_attr_store+0x13/0x20
       [<ffffffff81213c50>] sysfs_kf_write+0x40/0x50
       [<ffffffff81212f60>] kernfs_fop_write+0x150/0x1e0
       [<ffffffff81197613>] __vfs_write+0x23/0x120
       [<ffffffff81198740>] vfs_write+0xb0/0x190
       [<ffffffff81199a34>] SyS_write+0x44/0xa0
       [<ffffffff815c55a5>] entry_SYSCALL_64_fastpath+0x18/0xa8

-> #0 (&dev->lock){+.+.+.}:
       [<ffffffff810aac8c>] __lock_acquire+0x10fc/0x1270
       [<ffffffff810ab1f2>] lock_acquire+0xb2/0x1e0
       [<ffffffff815c087f>] mutex_lock_nested+0x5f/0x360
       [<ffffffffa03b1267>] ir_raw_handler_unregister+0x77/0xd0 [rc_core]
       [<ffffffffa03c8c05>] ir_lirc_codec_exit+0x10/0x12 [ir_lirc_codec]
       [<ffffffff810e1b88>] SyS_delete_module+0x168/0x220
       [<ffffffff815c55a5>] entry_SYSCALL_64_fastpath+0x18/0xa8

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(ir_raw_handler_lock);
                               lock(&dev->lock);
                               lock(ir_raw_handler_lock);
  lock(&dev->lock);

 *** DEADLOCK ***

1 lock held by rmmod/2542:
 #0:  (ir_raw_handler_lock){+.+.+.}, at: [<ffffffffa03b1212>]
			ir_raw_handler_unregister+0x22/0xd0 [rc_core]

stack backtrace:
CPU: 0 PID: 2542 Comm: rmmod Not tainted 4.7.0-next-20160729 #1
Hardware name: ZOTAC ZBOX-CI321NANO/ZBOX-CI321NANO, BIOS B246P105 06/01/2015
 0000000000000000 ffff88006e607cc0 ffffffff812715f5 ffffffff8232b230
 ffffffff8232b230 ffff88006e607d00 ffffffff810a846e 00000000790107f0
 ffff880079010818 ffff8800790107f0 1efeb9f4f0dd2e6f ffff880079010000
Call Trace:
 [<ffffffff812715f5>] dump_stack+0x68/0x93
 [<ffffffff810a846e>] print_circular_bug+0x1be/0x210
 [<ffffffff810aac8c>] __lock_acquire+0x10fc/0x1270
 [<ffffffff810bcead>] ? debug_lockdep_rcu_enabled+0x1d/0x20
 [<ffffffff810ab1f2>] lock_acquire+0xb2/0x1e0
 [<ffffffffa03b1267>] ? ir_raw_handler_unregister+0x77/0xd0 [rc_core]
 [<ffffffff815c087f>] mutex_lock_nested+0x5f/0x360
 [<ffffffffa03b1267>] ? ir_raw_handler_unregister+0x77/0xd0 [rc_core]
 [<ffffffff810a980e>] ? trace_hardirqs_on_caller+0xee/0x1b0
 [<ffffffffa03b1267>] ir_raw_handler_unregister+0x77/0xd0 [rc_core]
 [<ffffffffa03c8c05>] ir_lirc_codec_exit+0x10/0x12 [ir_lirc_codec]
 [<ffffffff810e1b88>] SyS_delete_module+0x168/0x220
 [<ffffffff815c55a5>] entry_SYSCALL_64_fastpath+0x18/0xa8

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
2016-09-22 11:23:13 -03:00
..
common [media] v4l2-tpg-core: drop SYCC, use higher precision 601 conversion matrix 2016-08-24 08:36:11 -03:00
dvb-core [media] get rid of a number of problems at the cross references 2016-09-22 10:00:23 -03:00
dvb-frontends [media] cxd2820r: convert to regmap api 2016-09-22 10:43:09 -03:00
firewire [media] dvb: modify core to implement interfaces/entities at MC new gen 2016-01-11 12:18:52 -02:00
i2c [media] s5c73m3: Fix entity function assignment for the OIF subdev 2016-09-22 10:15:36 -03:00
mmc
pci [media] constify i2c_algorithm structures 2016-09-19 16:27:02 -03:00
platform [media] exynos4-is: add of_platform_populate() call for FIMC-IS child devices 2016-09-22 10:20:06 -03:00
radio [media] constify i2c_algorithm structures 2016-09-19 16:27:02 -03:00
rc [media] media: rc: fix deadlock when module ir_lirc_codec is removed 2016-09-22 11:23:13 -03:00
spi [media] gs1662: make checkpatch happy 2016-09-19 14:39:49 -03:00
tuners [media] tuners: constify dvb_tuner_ops structures 2016-09-19 16:23:21 -03:00
usb [media] mxl111sf-tuner: constify dvb_tuner_ops structures 2016-09-19 16:28:26 -03:00
v4l2-core [media] SDI: add flag for SDI formats and SMPTE 125M definition 2016-09-19 14:34:41 -03:00
cec-edid.c [media] cec-edid: add module for EDID CEC helper functions 2016-06-28 09:45:51 -03:00
Kconfig [media] media Kconfig: improve the spi integration 2016-09-19 14:37:05 -03:00
Makefile [media] Add GS1662 driver, a video serializer 2016-09-19 14:36:24 -03:00
media-device.c [media] media: Add flags to tell whether to take graph mutex for an IOCTL 2016-09-22 10:28:40 -03:00
media-devnode.c [media] media: fix media devnode ioctl/syscall and unregister race 2016-06-15 17:59:28 -03:00
media-entity.c [media] media: Move media_device link_notify operation to an ops structure 2016-09-09 11:20:09 -03:00