em28xx DEADLOCK reported by lock debug

DISCUSSION Antti Palosaari 3 participants 10 messages Dec 18, 2013 – Dec 22, 2013

Subsystems (2)

Media (V4L/DVB) EM28XX VIDEO4LINUX driver

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Antti Palosaari

author

2013-12-18 16:04 UTC #0 lore raw

That same lock debug deadlock is still there (maybe ~4 times I report it during 2 years). Is that possible to fix easily at all?

Antti

joulu 18 17:56:37 localhost.localdomain kernel: usb 2-2: USB disconnect, device number 2
joulu 18 17:56:37 localhost.localdomain kernel: em28174 #0: disconnecting em28174 #0 video
joulu 18 17:56:37 localhost.localdomain kernel: joulu 18 17:56:37 localhost.localdomain kernel: ====================================================== joulu 18 17:56:37 localhost.localdomain kernel: [ INFO: possible circular locking dependency detected ]
joulu 18 17:56:37 localhost.localdomain kernel: 3.13.0-rc1+ #77 Tainted: G C O
joulu 18 17:56:37 localhost.localdomain kernel: -------------------------------------------------------
joulu 18 17:56:37 localhost.localdomain kernel: khubd/34 is trying to acquire lock:
joulu 18 17:56:37 localhost.localdomain kernel: (em28xx_devlist_mutex){+.+.+.}, at: [<ffffffffa06edd0d>] em28xx_close_extension+0x1d/0x70 [em28xx] joulu 18 17:56:37 localhost.localdomain kernel:
but task is already
holding lock:
joulu 18 17:56:37 localhost.localdomain kernel: (&dev->lock){+.+.+.}, at: [<ffffffffa06eb689>] em28xx_usb_disconnect+0x99/0x140 [em28xx] joulu 18 17:56:37 localhost.localdomain kernel:
which lock already
depends on the new lock.
joulu 18 17:56:37 localhost.localdomain kernel:
the existing dependency
chain (in reverse order) is:
joulu 18 17:56:37 localhost.localdomain kernel:

                                                -> #1 (&dev->lock){+.+.+.}:

joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816be5b7>] mutex_lock_nested+0x77/0x3d0 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa077b6d5>] em28xx_dvb_init+0x85/0x1b44 [em28xx_dvb] joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb908>] em28xx_register_extension+0x58/0xa0 [em28xx] joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa0783010>] 0xffffffffa0783010
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8100214a>] do_one_initcall+0xfa/0x1b0 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810eec72>] load_module+0x13c2/0x1a80 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810ef4c6>] SyS_finit_module+0x86/0xb0 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816ca729>] system_call_fastpath+0x16/0x1b joulu 18 17:56:37 localhost.localdomain kernel:

                                                -> #0

(em28xx_devlist_mutex){+.+.+.}:
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816be5b7>] mutex_lock_nested+0x77/0x3d0 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] em28xx_close_extension+0x1d/0x70 [em28xx] joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb6a3>] em28xx_usb_disconnect+0xb3/0x140 [em28xx] joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b7c87>] usb_unbind_interface+0x67/0x1d0 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814378ff>] __device_release_driver+0x7f/0xf0 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81437995>] device_release_driver+0x25/0x40 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814371fc>] bus_remove_device+0x11c/0x1a0 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81433c26>] device_del+0x136/0x1d0 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b5660>] usb_disable_device+0xb0/0x290 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814aa5f5>] usb_disconnect+0xb5/0x1d0 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814acfe6>] hub_port_connect_change+0xd6/0xad0 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814adcf3>] hub_events+0x313/0x9b0 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814ae3c5>] hub_thread+0x35/0x190 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8109044f>] kthread+0xff/0x120 joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816ca67c>] ret_from_fork+0x7c/0xb0 joulu 18 17:56:37 localhost.localdomain kernel:
other info that might
help us debug this:
joulu 18 17:56:37 localhost.localdomain kernel: Possible unsafe locking scenario:
joulu 18 17:56:37 localhost.localdomain kernel: CPU0
CPU1
joulu 18 17:56:37 localhost.localdomain kernel: ----

       ----
joulu 18 17:56:37 localhost.localdomain kernel:   lock(&dev->lock);
joulu 18 17:56:37 localhost.localdomain kernel: 
       lock(em28xx_devlist_mutex);
joulu 18 17:56:37 localhost.localdomain kernel: 
       lock(&dev->lock);
joulu 18 17:56:37 localhost.localdomain kernel: lock(em28xx_devlist_mutex);
joulu 18 17:56:37 localhost.localdomain kernel:
                                                 *** DEADLOCK ***
joulu 18 17:56:37 localhost.localdomain kernel: 4 locks held by khubd/34:
joulu 18 17:56:37 localhost.localdomain kernel:  #0: (&__lockdep_no_validate__){......}, at: [<ffffffff814ada94>] hub_events+0xb4/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel:  #1: (&__lockdep_no_validate__){......}, at: [<ffffffff814aa5a6>] usb_disconnect+0x66/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel:  #2: (&__lockdep_no_validate__){......}, at: [<ffffffff8143798d>] device_release_driver+0x1d/0x40
joulu 18 17:56:37 localhost.localdomain kernel:  #3: (&dev->lock){+.+.+.}, at: [<ffffffffa06eb689>] em28xx_usb_disconnect+0x99/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:
                                                stack backtrace:
joulu 18 17:56:37 localhost.localdomain kernel: CPU: 3 PID: 34 Comm: khubd Tainted: G         C O 3.13.0-rc1+ #77
joulu 18 17:56:37 localhost.localdomain kernel: Hardware name: System manufacturer System Product Name/M5A78L-M/USB3, BIOS 1503    11/14/2012
joulu 18 17:56:37 localhost.localdomain kernel:  ffffffff824f59f0 ffff88030dbb98e8 ffffffff816b8da9 ffffffff824f59f0
joulu 18 17:56:37 localhost.localdomain kernel:  ffff88030dbb9928 ffffffff816b2c9b ffff88030dbb9960 0000000000000003
joulu 18 17:56:37 localhost.localdomain kernel:  ffff88030da1afd0 0000000000000004 ffff88030da1a8a0 ffff88030da1afd0
joulu 18 17:56:37 localhost.localdomain kernel: Call Trace:
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff816b8da9>] dump_stack+0x4d/0x66
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff816b2c9b>] print_circular_bug+0x200/0x20e
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff8101c413>] ? native_sched_clock+0x13/0x80
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff810bb3a7>] ? __lock_acquire+0x3f7/0xc40
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffffa06edd0d>] ? em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff816be5b7>] mutex_lock_nested+0x77/0x3d0
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffffa06edd0d>] ? em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff810b9e6d>] ? trace_hardirqs_on+0xd/0x10
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffffa06edd0d>] ? em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffffa06eb689>] ? em28xx_usb_disconnect+0x99/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffffa06eb689>] ? em28xx_usb_disconnect+0x99/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffffa06edd0d>] em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffffa06eb6a3>] em28xx_usb_disconnect+0xb3/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff814b7c87>] usb_unbind_interface+0x67/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff814378ff>] __device_release_driver+0x7f/0xf0
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff81437995>] device_release_driver+0x25/0x40
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff814371fc>] bus_remove_device+0x11c/0x1a0
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff81433c26>] device_del+0x136/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff814b5660>] usb_disable_device+0xb0/0x290
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff814aa5f5>] usb_disconnect+0xb5/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff814acfe6>] hub_port_connect_change+0xd6/0xad0
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff814b40a4>] ? usb_control_msg+0xd4/0x110
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff814adcf3>] hub_events+0x313/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff814ae3c5>] hub_thread+0x35/0x190
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff810b12d0>] ? abort_exclusive_wait+0xb0/0xb0
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff814ae390>] ? hub_events+0x9b0/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff8109044f>] kthread+0xff/0x120
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff81090350>] ? kthread_create_on_node+0x250/0x250
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff816ca67c>] ret_from_fork+0x7c/0xb0
joulu 18 17:56:37 localhost.localdomain kernel:  [<ffffffff81090350>] ? kthread_create_on_node+0x250/0x250

joulu 18 17:56:37 localhost.localdomain kernel: tda18271 6-0060: destroying instance joulu 18 17:56:37 localhost.localdomain kernel: rc_unregister_device: Freed keycode table joulu 18 17:56:37 localhost.localdomain kernel: em28174 #0: V4L2 device video0 deregistered joulu 18 17:56:37 localhost.localdomain kernel: i2c i2c-6: adapter [em28174 #0] unregistered joulu 18 17:56:37 localhost.localdomain kernel: i2c i2c-5: adapter [em28174 #0] unregistered joulu 18 17:56:37 localhost.localdomain colord[603]: device removed: sysfs-PCTV_Systems-PCTV_290e

Signature · 1 line

http://palosaari.fi/

Frank Schäfer

2013-12-21 16:50 UTC #1 lore raw

Hi Antti,

thank you for reporting this issue.

Am 18.12.2013 17:04, schrieb Antti Palosaari:

Quoted 2 lines

That same lock debug deadlock is still there (maybe ~4 times I report it during 2 years). Is that possible to fix easily at all?

Patches are always welcome. ;)

Quoted 104 lines

Antti
joulu 18 17:56:37 localhost.localdomain kernel: usb 2-2: USB disconnect, device number 2
joulu 18 17:56:37 localhost.localdomain kernel: em28174 #0:
disconnecting em28174 #0 video
joulu 18 17:56:37 localhost.localdomain kernel: joulu 18 17:56:37 localhost.localdomain kernel:
======================================================
joulu 18 17:56:37 localhost.localdomain kernel: [ INFO: possible circular locking dependency detected ]
joulu 18 17:56:37 localhost.localdomain kernel: 3.13.0-rc1+ #77
Tainted: G         C O
joulu 18 17:56:37 localhost.localdomain kernel:
-------------------------------------------------------
joulu 18 17:56:37 localhost.localdomain kernel: khubd/34 is trying to acquire lock:
joulu 18 17:56:37 localhost.localdomain kernel:
(em28xx_devlist_mutex){+.+.+.}, at: [<ffffffffa06edd0d>] em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:
but task is already
holding lock:
joulu 18 17:56:37 localhost.localdomain kernel: (&dev->lock){+.+.+.},
at: [<ffffffffa06eb689>] em28xx_usb_disconnect+0x99/0x140 [em28xx] joulu 18 17:56:37 localhost.localdomain kernel:
which lock already
depends on the new lock.
joulu 18 17:56:37 localhost.localdomain kernel:
the existing
dependency chain (in reverse order) is:
joulu 18 17:56:37 localhost.localdomain kernel:
                                                -> #1
(&dev->lock){+.+.+.}:
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816be5b7>] mutex_lock_nested+0x77/0x3d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa077b6d5>] em28xx_dvb_init+0x85/0x1b44 [em28xx_dvb]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb908>] em28xx_register_extension+0x58/0xa0 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa0783010>] 0xffffffffa0783010
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8100214a>] do_one_initcall+0xfa/0x1b0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810eec72>] load_module+0x13c2/0x1a80
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810ef4c6>] SyS_finit_module+0x86/0xb0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816ca729>] system_call_fastpath+0x16/0x1b
joulu 18 17:56:37 localhost.localdomain kernel:
                                                -> #0
(em28xx_devlist_mutex){+.+.+.}:
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816be5b7>] mutex_lock_nested+0x77/0x3d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb6a3>] em28xx_usb_disconnect+0xb3/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b7c87>] usb_unbind_interface+0x67/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814378ff>] __device_release_driver+0x7f/0xf0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81437995>] device_release_driver+0x25/0x40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814371fc>] bus_remove_device+0x11c/0x1a0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81433c26>] device_del+0x136/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b5660>] usb_disable_device+0xb0/0x290
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814aa5f5>] usb_disconnect+0xb5/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814acfe6>] hub_port_connect_change+0xd6/0xad0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814adcf3>] hub_events+0x313/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814ae3c5>] hub_thread+0x35/0x190
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8109044f>] kthread+0xff/0x120
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816ca67c>] ret_from_fork+0x7c/0xb0
joulu 18 17:56:37 localhost.localdomain kernel:
other info that might
help us debug this:
joulu 18 17:56:37 localhost.localdomain kernel: Possible unsafe locking scenario:
joulu 18 17:56:37 localhost.localdomain kernel:        CPU0        CPU1
joulu 18 17:56:37 localhost.localdomain kernel:        ----        ----

Quoted 8 lines

joulu 18 17:56:37 localhost.localdomain kernel: lock(&dev->lock);
joulu 18 17:56:37 localhost.localdomain kernel:
lock(em28xx_devlist_mutex);
joulu 18 17:56:37 localhost.localdomain kernel: lock(&dev->lock);
joulu 18 17:56:37 localhost.localdomain kernel:
lock(em28xx_devlist_mutex);
joulu 18 17:56:37 localhost.localdomain kernel:
                                                 *** DEADLOCK ***

AFAICS, this deadlock can not occur. em28xx_usb_disconnect() calls flush_request_modules() before acquiring dev->lock which calls flush_work() to cancel module initialization. And flush_work() is actually flush_work_sync() these days, so module initialization should always be finished before dev->lock is acquired.

However, it would of course be nice to get this false warning fixed. Any suggestions ? :)

Regards,
Frank

Quoted 105 lines

joulu 18 17:56:37 localhost.localdomain kernel: 4 locks held by khubd/34:
joulu 18 17:56:37 localhost.localdomain kernel: #0:
(&__lockdep_no_validate__){......}, at: [<ffffffff814ada94>] hub_events+0xb4/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel: #1:
(&__lockdep_no_validate__){......}, at: [<ffffffff814aa5a6>] usb_disconnect+0x66/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: #2:
(&__lockdep_no_validate__){......}, at: [<ffffffff8143798d>] device_release_driver+0x1d/0x40
joulu 18 17:56:37 localhost.localdomain kernel: #3:
(&dev->lock){+.+.+.}, at: [<ffffffffa06eb689>] em28xx_usb_disconnect+0x99/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:
                                                stack backtrace:
joulu 18 17:56:37 localhost.localdomain kernel: CPU: 3 PID: 34 Comm:
khubd Tainted: G C O 3.13.0-rc1+ #77
joulu 18 17:56:37 localhost.localdomain kernel: Hardware name: System
manufacturer System Product Name/M5A78L-M/USB3, BIOS 1503 11/14/2012
joulu 18 17:56:37 localhost.localdomain kernel: ffffffff824f59f0 ffff88030dbb98e8 ffffffff816b8da9 ffffffff824f59f0
joulu 18 17:56:37 localhost.localdomain kernel: ffff88030dbb9928 ffffffff816b2c9b ffff88030dbb9960 0000000000000003
joulu 18 17:56:37 localhost.localdomain kernel: ffff88030da1afd0 0000000000000004 ffff88030da1a8a0 ffff88030da1afd0
joulu 18 17:56:37 localhost.localdomain kernel: Call Trace:
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816b8da9>] dump_stack+0x4d/0x66
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816b2c9b>] print_circular_bug+0x200/0x20e
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8101c413>] ? native_sched_clock+0x13/0x80
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb3a7>] ? __lock_acquire+0x3f7/0xc40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] ? em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816be5b7>] mutex_lock_nested+0x77/0x3d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] ? em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b9e6d>] ? trace_hardirqs_on+0xd/0x10
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] ? em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb689>] ? em28xx_usb_disconnect+0x99/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb689>] ? em28xx_usb_disconnect+0x99/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb6a3>] em28xx_usb_disconnect+0xb3/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b7c87>] usb_unbind_interface+0x67/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814378ff>] __device_release_driver+0x7f/0xf0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81437995>] device_release_driver+0x25/0x40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814371fc>] bus_remove_device+0x11c/0x1a0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81433c26>] device_del+0x136/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b5660>] usb_disable_device+0xb0/0x290
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814aa5f5>] usb_disconnect+0xb5/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814acfe6>] hub_port_connect_change+0xd6/0xad0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b40a4>] ? usb_control_msg+0xd4/0x110
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814adcf3>] hub_events+0x313/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814ae3c5>] hub_thread+0x35/0x190
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b12d0>] ? abort_exclusive_wait+0xb0/0xb0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814ae390>] ? hub_events+0x9b0/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8109044f>] kthread+0xff/0x120
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81090350>] ? kthread_create_on_node+0x250/0x250
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816ca67c>] ret_from_fork+0x7c/0xb0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81090350>] ? kthread_create_on_node+0x250/0x250
joulu 18 17:56:37 localhost.localdomain kernel: tda18271 6-0060:
destroying instance
joulu 18 17:56:37 localhost.localdomain kernel: rc_unregister_device:
Freed keycode table
joulu 18 17:56:37 localhost.localdomain kernel: em28174 #0: V4L2 device video0 deregistered
joulu 18 17:56:37 localhost.localdomain kernel: i2c i2c-6: adapter [em28174 #0] unregistered
joulu 18 17:56:37 localhost.localdomain kernel: i2c i2c-5: adapter [em28174 #0] unregistered
joulu 18 17:56:37 localhost.localdomain colord[603]: device removed:
sysfs-PCTV_Systems-PCTV_290e

Antti Palosaari

author

2013-12-21 19:55 UTC #2 lore raw

Quoted 9 lines · Frank Schäfer

Hi Antti,
thank you for reporting this issue.
Am 18.12.2013 17:04, schrieb Antti Palosaari:
Quoted 2 lines
That same lock debug deadlock is still there (maybe ~4 times I report it during 2 years). Is that possible to fix easily at all?
Patches are always welcome. ;)

haha, I cannot simply learn every driver I meet some problems...

But now, when V4L2 SDR module was added RTL28xxU DVB module I see quite similar looking bug warning here too :S

I wonder if that is same...

joulu 21 21:49:19 localhost.localdomain kernel: usb 2-2: rtl2832_sdr_queue_setup: nbuffers=32 sizes[0]=131072
joulu 21 21:49:19 localhost.localdomain kernel: joulu 21 21:49:19 localhost.localdomain kernel: ====================================================== joulu 21 21:49:19 localhost.localdomain kernel: [ INFO: possible circular locking dependency detected ]
joulu 21 21:49:19 localhost.localdomain kernel: 3.13.0-rc1+ #77 Tainted: G C O
joulu 21 21:49:19 localhost.localdomain kernel: -------------------------------------------------------
joulu 21 21:49:19 localhost.localdomain kernel: python/15284 is trying to acquire lock:
joulu 21 21:49:19 localhost.localdomain kernel: (&s->vb_queue_lock){+.+.+.}, at: [<ffffffffa06d0de3>] vb2_fop_mmap+0x33/0x90 [videobuf2_core] joulu 21 21:49:19 localhost.localdomain kernel:
but task is already
holding lock:
joulu 21 21:49:19 localhost.localdomain kernel: (&mm->mmap_sem){++++++}, at: [<ffffffff8117825f>] vm_mmap_pgoff+0x6f/0xc0 joulu 21 21:49:19 localhost.localdomain kernel:
which lock already
depends on the new lock.
joulu 21 21:49:19 localhost.localdomain kernel:
the existing dependency
chain (in reverse order) is:
joulu 21 21:49:19 localhost.localdomain kernel:

                                                -> #1

(&mm->mmap_sem){++++++}:
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff81181f3c>] might_fault+0x8c/0xb0 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06a9dba>] video_usercopy+0xba/0x4e0 [videodev] joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06aa1f5>] video_ioctl2+0x15/0x20 [videodev] joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06a3e73>] v4l2_ioctl+0x153/0x240 [videodev] joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff811e0590>] do_vfs_ioctl+0x300/0x520 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff811e0831>] SyS_ioctl+0x81/0xa0 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff816ca729>] system_call_fastpath+0x16/0x1b joulu 21 21:49:19 localhost.localdomain kernel:

                                                -> #0

(&s->vb_queue_lock){+.+.+.}:
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff816bf1c7>] mutex_lock_interruptible_nested+0x77/0x460 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06d0de3>] vb2_fop_mmap+0x33/0x90 [videobuf2_core] joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06a385a>] v4l2_mmap+0x5a/0xa0 [videodev] joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff8118da7d>] mmap_region+0x3cd/0x5a0 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff8118dfa7>] do_mmap_pgoff+0x357/0x3e0 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff81178280>] vm_mmap_pgoff+0x90/0xc0 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff8118c553>] SyS_mmap_pgoff+0x1d3/0x270 joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810191a2>] SyS_mmap+0x22/0x30
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff816ca729>] system_call_fastpath+0x16/0x1b joulu 21 21:49:19 localhost.localdomain kernel:
other info that might
help us debug this:
joulu 21 21:49:19 localhost.localdomain kernel: Possible unsafe locking scenario:
joulu 21 21:49:19 localhost.localdomain kernel: CPU0
CPU1
joulu 21 21:49:19 localhost.localdomain kernel: ----

       ----
joulu 21 21:49:19 localhost.localdomain kernel:   lock(&mm->mmap_sem);
joulu 21 21:49:19 localhost.localdomain kernel: 
       lock(&s->vb_queue_lock);
joulu 21 21:49:19 localhost.localdomain kernel: 
       lock(&mm->mmap_sem);
joulu 21 21:49:19 localhost.localdomain kernel:   lock(&s->vb_queue_lock);
joulu 21 21:49:19 localhost.localdomain kernel:
                                                 *** DEADLOCK ***
joulu 21 21:49:19 localhost.localdomain kernel: 1 lock held by python/15284:
joulu 21 21:49:19 localhost.localdomain kernel:  #0: (&mm->mmap_sem){++++++}, at: [<ffffffff8117825f>] vm_mmap_pgoff+0x6f/0xc0
joulu 21 21:49:19 localhost.localdomain kernel:
                                                stack backtrace:
joulu 21 21:49:19 localhost.localdomain kernel: CPU: 3 PID: 15284 Comm: python Tainted: G         C O 3.13.0-rc1+ #77
joulu 21 21:49:19 localhost.localdomain kernel: Hardware name: System manufacturer System Product Name/M5A78L-M/USB3, BIOS 1503    11/14/2012
joulu 21 21:49:19 localhost.localdomain kernel:  ffffffff824fab50 ffff88025c5efb68 ffffffff816b8da9 ffffffff824fab50
joulu 21 21:49:19 localhost.localdomain kernel:  ffff88025c5efba8 ffffffff816b2c9b ffff88025c5efbe0 0000000000000000
joulu 21 21:49:19 localhost.localdomain kernel:  ffff880202ce6c18 0000000000000001 ffff880202ce6590 ffff880202ce6c18
joulu 21 21:49:19 localhost.localdomain kernel: Call Trace:
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff816b8da9>] dump_stack+0x4d/0x66
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff816b2c9b>] print_circular_bug+0x200/0x20e
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff810bb3a7>] ? __lock_acquire+0x3f7/0xc40
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff8101c413>] ? native_sched_clock+0x13/0x80
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff81182706>] ? __do_fault+0x236/0x510
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff8101c413>] ? native_sched_clock+0x13/0x80
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff8101c489>] ? sched_clock+0x9/0x10
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffffa06d0de3>] ? vb2_fop_mmap+0x33/0x90 [videobuf2_core]
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff816bf1c7>] mutex_lock_interruptible_nested+0x77/0x460
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffffa06d0de3>] ? vb2_fop_mmap+0x33/0x90 [videobuf2_core]
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffffa06d0de3>] ? vb2_fop_mmap+0x33/0x90 [videobuf2_core]
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffffa06d0de3>] vb2_fop_mmap+0x33/0x90 [videobuf2_core]
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffffa06a385a>] v4l2_mmap+0x5a/0xa0 [videodev]
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff8118da7d>] mmap_region+0x3cd/0x5a0
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff8118dfa7>] do_mmap_pgoff+0x357/0x3e0
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff81178280>] vm_mmap_pgoff+0x90/0xc0
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff8118c553>] SyS_mmap_pgoff+0x1d3/0x270
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff810191a2>] SyS_mmap+0x22/0x30
joulu 21 21:49:19 localhost.localdomain kernel:  [<ffffffff816ca729>] system_call_fastpath+0x16/0x1b

joulu 21 21:49:19 localhost.localdomain kernel: usb 2-2: rtl2832_sdr_start_streaming:
joulu 21 21:49:19 localhost.localdomain kernel: usb 2-2: rtl2832u_power_ctrl: onoff=1 joulu 21 21:49:19 localhost.localdomain kernel: usb 2-2: rtl28xxu_ctrl_msg: c0 00 01 30 00 02 01 00 <<< 18

Quoted 232 lines

Quoted 105 lines
Antti
joulu 18 17:56:37 localhost.localdomain kernel: usb 2-2: USB disconnect, device number 2
joulu 18 17:56:37 localhost.localdomain kernel: em28174 #0:
disconnecting em28174 #0 video
joulu 18 17:56:37 localhost.localdomain kernel: joulu 18 17:56:37 localhost.localdomain kernel:
======================================================
joulu 18 17:56:37 localhost.localdomain kernel: [ INFO: possible circular locking dependency detected ]
joulu 18 17:56:37 localhost.localdomain kernel: 3.13.0-rc1+ #77
Tainted: G         C O
joulu 18 17:56:37 localhost.localdomain kernel:
-------------------------------------------------------
joulu 18 17:56:37 localhost.localdomain kernel: khubd/34 is trying to acquire lock:
joulu 18 17:56:37 localhost.localdomain kernel:
(em28xx_devlist_mutex){+.+.+.}, at: [<ffffffffa06edd0d>] em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:
but task is already
holding lock:
joulu 18 17:56:37 localhost.localdomain kernel: (&dev->lock){+.+.+.},
at: [<ffffffffa06eb689>] em28xx_usb_disconnect+0x99/0x140 [em28xx] joulu 18 17:56:37 localhost.localdomain kernel:
which lock already
depends on the new lock.
joulu 18 17:56:37 localhost.localdomain kernel:
the existing
dependency chain (in reverse order) is:
joulu 18 17:56:37 localhost.localdomain kernel:
                                                 -> #1
(&dev->lock){+.+.+.}:
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816be5b7>] mutex_lock_nested+0x77/0x3d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa077b6d5>] em28xx_dvb_init+0x85/0x1b44 [em28xx_dvb]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb908>] em28xx_register_extension+0x58/0xa0 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa0783010>] 0xffffffffa0783010
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8100214a>] do_one_initcall+0xfa/0x1b0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810eec72>] load_module+0x13c2/0x1a80
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810ef4c6>] SyS_finit_module+0x86/0xb0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816ca729>] system_call_fastpath+0x16/0x1b
joulu 18 17:56:37 localhost.localdomain kernel:
                                                 -> #0
(em28xx_devlist_mutex){+.+.+.}:
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816be5b7>] mutex_lock_nested+0x77/0x3d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb6a3>] em28xx_usb_disconnect+0xb3/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b7c87>] usb_unbind_interface+0x67/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814378ff>] __device_release_driver+0x7f/0xf0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81437995>] device_release_driver+0x25/0x40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814371fc>] bus_remove_device+0x11c/0x1a0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81433c26>] device_del+0x136/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b5660>] usb_disable_device+0xb0/0x290
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814aa5f5>] usb_disconnect+0xb5/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814acfe6>] hub_port_connect_change+0xd6/0xad0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814adcf3>] hub_events+0x313/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814ae3c5>] hub_thread+0x35/0x190
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8109044f>] kthread+0xff/0x120
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816ca67c>] ret_from_fork+0x7c/0xb0
joulu 18 17:56:37 localhost.localdomain kernel:
other info that might
help us debug this:
joulu 18 17:56:37 localhost.localdomain kernel: Possible unsafe locking scenario:
joulu 18 17:56:37 localhost.localdomain kernel:        CPU0        CPU1
joulu 18 17:56:37 localhost.localdomain kernel:        ----        ----
Quoted 8 lines
joulu 18 17:56:37 localhost.localdomain kernel: lock(&dev->lock);
joulu 18 17:56:37 localhost.localdomain kernel:
lock(em28xx_devlist_mutex);
joulu 18 17:56:37 localhost.localdomain kernel: lock(&dev->lock);
joulu 18 17:56:37 localhost.localdomain kernel:
lock(em28xx_devlist_mutex);
joulu 18 17:56:37 localhost.localdomain kernel:
                                                  *** DEADLOCK ***
AFAICS, this deadlock can not occur. em28xx_usb_disconnect() calls flush_request_modules() before acquiring dev->lock which calls flush_work() to cancel module initialization. And flush_work() is actually flush_work_sync() these days, so module initialization should always be finished before dev->lock is acquired.
However, it would of course be nice to get this false warning fixed. Any suggestions ? :)
Regards,
Frank
Quoted 105 lines
joulu 18 17:56:37 localhost.localdomain kernel: 4 locks held by khubd/34:
joulu 18 17:56:37 localhost.localdomain kernel: #0:
(&__lockdep_no_validate__){......}, at: [<ffffffff814ada94>] hub_events+0xb4/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel: #1:
(&__lockdep_no_validate__){......}, at: [<ffffffff814aa5a6>] usb_disconnect+0x66/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: #2:
(&__lockdep_no_validate__){......}, at: [<ffffffff8143798d>] device_release_driver+0x1d/0x40
joulu 18 17:56:37 localhost.localdomain kernel: #3:
(&dev->lock){+.+.+.}, at: [<ffffffffa06eb689>] em28xx_usb_disconnect+0x99/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:
                                                 stack backtrace:
joulu 18 17:56:37 localhost.localdomain kernel: CPU: 3 PID: 34 Comm:
khubd Tainted: G C O 3.13.0-rc1+ #77
joulu 18 17:56:37 localhost.localdomain kernel: Hardware name: System
manufacturer System Product Name/M5A78L-M/USB3, BIOS 1503 11/14/2012
joulu 18 17:56:37 localhost.localdomain kernel: ffffffff824f59f0 ffff88030dbb98e8 ffffffff816b8da9 ffffffff824f59f0
joulu 18 17:56:37 localhost.localdomain kernel: ffff88030dbb9928 ffffffff816b2c9b ffff88030dbb9960 0000000000000003
joulu 18 17:56:37 localhost.localdomain kernel: ffff88030da1afd0 0000000000000004 ffff88030da1a8a0 ffff88030da1afd0
joulu 18 17:56:37 localhost.localdomain kernel: Call Trace:
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816b8da9>] dump_stack+0x4d/0x66
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816b2c9b>] print_circular_bug+0x200/0x20e
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8101c413>] ? native_sched_clock+0x13/0x80
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb3a7>] ? __lock_acquire+0x3f7/0xc40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] ? em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816be5b7>] mutex_lock_nested+0x77/0x3d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] ? em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b9e6d>] ? trace_hardirqs_on+0xd/0x10
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] ? em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb689>] ? em28xx_usb_disconnect+0x99/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb689>] ? em28xx_usb_disconnect+0x99/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb6a3>] em28xx_usb_disconnect+0xb3/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b7c87>] usb_unbind_interface+0x67/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814378ff>] __device_release_driver+0x7f/0xf0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81437995>] device_release_driver+0x25/0x40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814371fc>] bus_remove_device+0x11c/0x1a0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81433c26>] device_del+0x136/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b5660>] usb_disable_device+0xb0/0x290
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814aa5f5>] usb_disconnect+0xb5/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814acfe6>] hub_port_connect_change+0xd6/0xad0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b40a4>] ? usb_control_msg+0xd4/0x110
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814adcf3>] hub_events+0x313/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814ae3c5>] hub_thread+0x35/0x190
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b12d0>] ? abort_exclusive_wait+0xb0/0xb0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814ae390>] ? hub_events+0x9b0/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8109044f>] kthread+0xff/0x120
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81090350>] ? kthread_create_on_node+0x250/0x250
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816ca67c>] ret_from_fork+0x7c/0xb0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81090350>] ? kthread_create_on_node+0x250/0x250
joulu 18 17:56:37 localhost.localdomain kernel: tda18271 6-0060:
destroying instance
joulu 18 17:56:37 localhost.localdomain kernel: rc_unregister_device:
Freed keycode table
joulu 18 17:56:37 localhost.localdomain kernel: em28174 #0: V4L2 device video0 deregistered
joulu 18 17:56:37 localhost.localdomain kernel: i2c i2c-6: adapter [em28174 #0] unregistered
joulu 18 17:56:37 localhost.localdomain kernel: i2c i2c-5: adapter [em28174 #0] unregistered
joulu 18 17:56:37 localhost.localdomain colord[603]: device removed:
sysfs-PCTV_Systems-PCTV_290e

Signature · 1 line

http://palosaari.fi/

Frank Schäfer

2013-12-22 13:50 UTC #3 lore raw

Am 21.12.2013 20:55, schrieb Antti Palosaari:

Quoted 5 lines · Frank Schäfer

Quoted 4 lines
Hi Antti,
thank you for reporting this issue.

Quoted 7 lines

Quoted 5 lines
Am 18.12.2013 17:04, schrieb Antti Palosaari:
Quoted 2 lines
That same lock debug deadlock is still there (maybe ~4 times I report it during 2 years). Is that possible to fix easily at all?
Patches are always welcome. ;)
haha, I cannot simply learn every driver I meet some problems...

Hint:

If you report a bug ~4 times in 2 years but never get a reply, it usually means
a) nobody cares
b) nobody has the resources (time, knowledge) to fix it.

So you either have to live with this issue or to fix it yourself.

Quoted 97 lines

But now, when V4L2 SDR module was added RTL28xxU DVB module I see quite similar looking bug warning here too :
I wonder if that is same...
joulu 21 21:49:19 localhost.localdomain kernel: usb 2-2:
rtl2832_sdr_queue_setup: nbuffers=32 sizes[0]=131072 joulu 21 21:49:19 localhost.localdomain kernel: joulu 21 21:49:19 localhost.localdomain kernel:
======================================================
joulu 21 21:49:19 localhost.localdomain kernel: [ INFO: possible circular locking dependency detected ]
joulu 21 21:49:19 localhost.localdomain kernel: 3.13.0-rc1+ #77
Tainted: G         C O
joulu 21 21:49:19 localhost.localdomain kernel:
-------------------------------------------------------
joulu 21 21:49:19 localhost.localdomain kernel: python/15284 is trying to acquire lock:
joulu 21 21:49:19 localhost.localdomain kernel:
(&s->vb_queue_lock){+.+.+.}, at: [<ffffffffa06d0de3>] vb2_fop_mmap+0x33/0x90 [videobuf2_core]
joulu 21 21:49:19 localhost.localdomain kernel:
but task is already
holding lock:
joulu 21 21:49:19 localhost.localdomain kernel:
(&mm->mmap_sem){++++++}, at: [<ffffffff8117825f>] vm_mmap_pgoff+0x6f/0xc0 joulu 21 21:49:19 localhost.localdomain kernel:
which lock already
depends on the new lock.
joulu 21 21:49:19 localhost.localdomain kernel:
the existing
dependency chain (in reverse order) is:
joulu 21 21:49:19 localhost.localdomain kernel:
                                                -> #1
(&mm->mmap_sem){++++++}:
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff81181f3c>] might_fault+0x8c/0xb0
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06a9dba>] video_usercopy+0xba/0x4e0 [videodev]
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06aa1f5>] video_ioctl2+0x15/0x20 [videodev]
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06a3e73>] v4l2_ioctl+0x153/0x240 [videodev]
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff811e0590>] do_vfs_ioctl+0x300/0x520
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff811e0831>] SyS_ioctl+0x81/0xa0
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff816ca729>] system_call_fastpath+0x16/0x1b
joulu 21 21:49:19 localhost.localdomain kernel:
                                                -> #0
(&s->vb_queue_lock){+.+.+.}:
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff816bf1c7>] mutex_lock_interruptible_nested+0x77/0x460
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06d0de3>] vb2_fop_mmap+0x33/0x90 [videobuf2_core]
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06a385a>] v4l2_mmap+0x5a/0xa0 [videodev]
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff8118da7d>] mmap_region+0x3cd/0x5a0
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff8118dfa7>] do_mmap_pgoff+0x357/0x3e0
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff81178280>] vm_mmap_pgoff+0x90/0xc0
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff8118c553>] SyS_mmap_pgoff+0x1d3/0x270
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810191a2>] SyS_mmap+0x22/0x30
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff816ca729>] system_call_fastpath+0x16/0x1b
joulu 21 21:49:19 localhost.localdomain kernel:
other info that might
help us debug this:
joulu 21 21:49:19 localhost.localdomain kernel: Possible unsafe locking scenario:
joulu 21 21:49:19 localhost.localdomain kernel:        CPU0        CPU1
joulu 21 21:49:19 localhost.localdomain kernel:        ----        ----
joulu 21 21:49:19 localhost.localdomain kernel: lock(&mm->mmap_sem);
joulu 21 21:49:19 localhost.localdomain kernel:
lock(&s->vb_queue_lock);
joulu 21 21:49:19 localhost.localdomain kernel:
lock(&mm->mmap_sem);
joulu 21 21:49:19 localhost.localdomain kernel:
lock(&s->vb_queue_lock);
joulu 21 21:49:19 localhost.localdomain kernel:

Quoted 1 line

                                                 *** DEADLOCK ***

I can't see any relationship with the em28xx issue, except that both warnings are about possible deadlocks. ;)
I'm not even sure if it is a RTL28xxU issue.
Sorry, -ENORESOURCES for this.

Regards,
Frank

Quoted 307 lines

joulu 21 21:49:19 localhost.localdomain kernel: 1 lock held by python/15284:
joulu 21 21:49:19 localhost.localdomain kernel: #0:
(&mm->mmap_sem){++++++}, at: [<ffffffff8117825f>] vm_mmap_pgoff+0x6f/0xc0 joulu 21 21:49:19 localhost.localdomain kernel:
                                                stack backtrace:
joulu 21 21:49:19 localhost.localdomain kernel: CPU: 3 PID: 15284
Comm: python Tainted: G C O 3.13.0-rc1+ #77
joulu 21 21:49:19 localhost.localdomain kernel: Hardware name: System
manufacturer System Product Name/M5A78L-M/USB3, BIOS 1503 11/14/2012
joulu 21 21:49:19 localhost.localdomain kernel: ffffffff824fab50 ffff88025c5efb68 ffffffff816b8da9 ffffffff824fab50
joulu 21 21:49:19 localhost.localdomain kernel: ffff88025c5efba8 ffffffff816b2c9b ffff88025c5efbe0 0000000000000000
joulu 21 21:49:19 localhost.localdomain kernel: ffff880202ce6c18 0000000000000001 ffff880202ce6590 ffff880202ce6c18
joulu 21 21:49:19 localhost.localdomain kernel: Call Trace:
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff816b8da9>] dump_stack+0x4d/0x66
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff816b2c9b>] print_circular_bug+0x200/0x20e
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810bb3a7>] ? __lock_acquire+0x3f7/0xc40
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff8101c413>] ? native_sched_clock+0x13/0x80
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff81182706>] ? __do_fault+0x236/0x510
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff8101c413>] ? native_sched_clock+0x13/0x80
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff8101c489>] ? sched_clock+0x9/0x10
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06d0de3>] ? vb2_fop_mmap+0x33/0x90 [videobuf2_core]
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff816bf1c7>] mutex_lock_interruptible_nested+0x77/0x460
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06d0de3>] ? vb2_fop_mmap+0x33/0x90 [videobuf2_core]
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06d0de3>] ? vb2_fop_mmap+0x33/0x90 [videobuf2_core]
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06d0de3>] vb2_fop_mmap+0x33/0x90 [videobuf2_core]
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffffa06a385a>] v4l2_mmap+0x5a/0xa0 [videodev]
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff8118da7d>] mmap_region+0x3cd/0x5a0
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff8118dfa7>] do_mmap_pgoff+0x357/0x3e0
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff81178280>] vm_mmap_pgoff+0x90/0xc0
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff8118c553>] SyS_mmap_pgoff+0x1d3/0x270
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff810191a2>] SyS_mmap+0x22/0x30
joulu 21 21:49:19 localhost.localdomain kernel: [<ffffffff816ca729>] system_call_fastpath+0x16/0x1b
joulu 21 21:49:19 localhost.localdomain kernel: usb 2-2:
rtl2832_sdr_start_streaming:
joulu 21 21:49:19 localhost.localdomain kernel: usb 2-2:
rtl2832u_power_ctrl: onoff=1
joulu 21 21:49:19 localhost.localdomain kernel: usb 2-2:
rtl28xxu_ctrl_msg: c0 00 01 30 00 02 01 00 <<< 18
Quoted 234 lines
Quoted 113 lines
Antti
joulu 18 17:56:37 localhost.localdomain kernel: usb 2-2: USB disconnect, device number 2
joulu 18 17:56:37 localhost.localdomain kernel: em28174 #0:
disconnecting em28174 #0 video
joulu 18 17:56:37 localhost.localdomain kernel: joulu 18 17:56:37 localhost.localdomain kernel:
======================================================
joulu 18 17:56:37 localhost.localdomain kernel: [ INFO: possible circular locking dependency detected ]
joulu 18 17:56:37 localhost.localdomain kernel: 3.13.0-rc1+ #77
Tainted: G         C O
joulu 18 17:56:37 localhost.localdomain kernel:
-------------------------------------------------------
joulu 18 17:56:37 localhost.localdomain kernel: khubd/34 is trying to acquire lock:
joulu 18 17:56:37 localhost.localdomain kernel:
(em28xx_devlist_mutex){+.+.+.}, at: [<ffffffffa06edd0d>] em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:
but task is already
holding lock:
joulu 18 17:56:37 localhost.localdomain kernel: (&dev->lock){+.+.+.},
at: [<ffffffffa06eb689>] em28xx_usb_disconnect+0x99/0x140 [em28xx] joulu 18 17:56:37 localhost.localdomain kernel:
which lock already
depends on the new lock.
joulu 18 17:56:37 localhost.localdomain kernel:
the existing
dependency chain (in reverse order) is:
joulu 18 17:56:37 localhost.localdomain kernel:
                                                 -> #1
(&dev->lock){+.+.+.}:
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816be5b7>] mutex_lock_nested+0x77/0x3d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa077b6d5>] em28xx_dvb_init+0x85/0x1b44 [em28xx_dvb]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb908>] em28xx_register_extension+0x58/0xa0 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa0783010>] 0xffffffffa0783010
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8100214a>] do_one_initcall+0xfa/0x1b0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810eec72>] load_module+0x13c2/0x1a80
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810ef4c6>] SyS_finit_module+0x86/0xb0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816ca729>] system_call_fastpath+0x16/0x1b
joulu 18 17:56:37 localhost.localdomain kernel:
                                                 -> #0
(em28xx_devlist_mutex){+.+.+.}:
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816be5b7>] mutex_lock_nested+0x77/0x3d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb6a3>] em28xx_usb_disconnect+0xb3/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b7c87>] usb_unbind_interface+0x67/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814378ff>] __device_release_driver+0x7f/0xf0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81437995>] device_release_driver+0x25/0x40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814371fc>] bus_remove_device+0x11c/0x1a0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81433c26>] device_del+0x136/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b5660>] usb_disable_device+0xb0/0x290
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814aa5f5>] usb_disconnect+0xb5/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814acfe6>] hub_port_connect_change+0xd6/0xad0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814adcf3>] hub_events+0x313/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814ae3c5>] hub_thread+0x35/0x190
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8109044f>] kthread+0xff/0x120
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816ca67c>] ret_from_fork+0x7c/0xb0
joulu 18 17:56:37 localhost.localdomain kernel:
other info that might
help us debug this:
joulu 18 17:56:37 localhost.localdomain kernel: Possible unsafe locking scenario:
joulu 18 17:56:37 localhost.localdomain kernel:        CPU0        CPU1
joulu 18 17:56:37 localhost.localdomain kernel:        ----        ----
joulu 18 17:56:37 localhost.localdomain kernel: lock(&dev->lock);
joulu 18 17:56:37 localhost.localdomain kernel:
lock(em28xx_devlist_mutex);
joulu 18 17:56:37 localhost.localdomain kernel:
lock(&dev->lock);
joulu 18 17:56:37 localhost.localdomain kernel:
lock(em28xx_devlist_mutex);
joulu 18 17:56:37 localhost.localdomain kernel:
Quoted 1 line
                                                  *** DEADLOCK ***
AFAICS, this deadlock can not occur. em28xx_usb_disconnect() calls flush_request_modules() before acquiring dev->lock which calls flush_work() to cancel module initialization. And flush_work() is actually flush_work_sync() these days, so module initialization should always be finished before dev->lock is acquired.
However, it would of course be nice to get this false warning fixed. Any suggestions ? :)
Regards,
Frank
Quoted 106 lines
joulu 18 17:56:37 localhost.localdomain kernel: 4 locks held by khubd/34:
joulu 18 17:56:37 localhost.localdomain kernel: #0:
(&__lockdep_no_validate__){......}, at: [<ffffffff814ada94>] hub_events+0xb4/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel: #1:
(&__lockdep_no_validate__){......}, at: [<ffffffff814aa5a6>] usb_disconnect+0x66/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: #2:
(&__lockdep_no_validate__){......}, at: [<ffffffff8143798d>] device_release_driver+0x1d/0x40
joulu 18 17:56:37 localhost.localdomain kernel: #3:
(&dev->lock){+.+.+.}, at: [<ffffffffa06eb689>] em28xx_usb_disconnect+0x99/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel:
                                                 stack backtrace:
joulu 18 17:56:37 localhost.localdomain kernel: CPU: 3 PID: 34 Comm:
khubd Tainted: G C O 3.13.0-rc1+ #77
joulu 18 17:56:37 localhost.localdomain kernel: Hardware name: System
manufacturer System Product Name/M5A78L-M/USB3, BIOS 1503 11/14/2012
joulu 18 17:56:37 localhost.localdomain kernel: ffffffff824f59f0 ffff88030dbb98e8 ffffffff816b8da9 ffffffff824f59f0
joulu 18 17:56:37 localhost.localdomain kernel: ffff88030dbb9928 ffffffff816b2c9b ffff88030dbb9960 0000000000000003
joulu 18 17:56:37 localhost.localdomain kernel: ffff88030da1afd0 0000000000000004 ffff88030da1a8a0 ffff88030da1afd0
joulu 18 17:56:37 localhost.localdomain kernel: Call Trace:
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816b8da9>] dump_stack+0x4d/0x66
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816b2c9b>] print_circular_bug+0x200/0x20e
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8101c413>] ? native_sched_clock+0x13/0x80
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bb3a7>] ? __lock_acquire+0x3f7/0xc40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810bbca0>] lock_acquire+0xb0/0x150
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] ? em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816be5b7>] mutex_lock_nested+0x77/0x3d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] ? em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b9e6d>] ? trace_hardirqs_on+0xd/0x10
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] ? em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb689>] ? em28xx_usb_disconnect+0x99/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb689>] ? em28xx_usb_disconnect+0x99/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06edd0d>] em28xx_close_extension+0x1d/0x70 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffffa06eb6a3>] em28xx_usb_disconnect+0xb3/0x140 [em28xx]
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b7c87>] usb_unbind_interface+0x67/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814378ff>] __device_release_driver+0x7f/0xf0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81437995>] device_release_driver+0x25/0x40
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814371fc>] bus_remove_device+0x11c/0x1a0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81433c26>] device_del+0x136/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b5660>] usb_disable_device+0xb0/0x290
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814aa5f5>] usb_disconnect+0xb5/0x1d0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814acfe6>] hub_port_connect_change+0xd6/0xad0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814b40a4>] ? usb_control_msg+0xd4/0x110
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814adcf3>] hub_events+0x313/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814ae3c5>] hub_thread+0x35/0x190
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff810b12d0>] ? abort_exclusive_wait+0xb0/0xb0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff814ae390>] ? hub_events+0x9b0/0x9b0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff8109044f>] kthread+0xff/0x120
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81090350>] ? kthread_create_on_node+0x250/0x250
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff816ca67c>] ret_from_fork+0x7c/0xb0
joulu 18 17:56:37 localhost.localdomain kernel: [<ffffffff81090350>] ? kthread_create_on_node+0x250/0x250
joulu 18 17:56:37 localhost.localdomain kernel: tda18271 6-0060:
destroying instance
joulu 18 17:56:37 localhost.localdomain kernel: rc_unregister_device:
Freed keycode table
joulu 18 17:56:37 localhost.localdomain kernel: em28174 #0: V4L2 device video0 deregistered
joulu 18 17:56:37 localhost.localdomain kernel: i2c i2c-6: adapter [em28174 #0] unregistered
joulu 18 17:56:37 localhost.localdomain kernel: i2c i2c-5: adapter [em28174 #0] unregistered
joulu 18 17:56:37 localhost.localdomain colord[603]: device removed:
sysfs-PCTV_Systems-PCTV_290e

Antti Palosaari

author

2013-12-22 14:34 UTC #4 lore raw

Quoted 13 lines · Frank Schäfer

Am 21.12.2013 20:55, schrieb Antti Palosaari:
Quoted 5 lines · Frank Schäfer
Quoted 4 lines
Hi Antti,
thank you for reporting this issue.
Quoted 7 lines
Quoted 5 lines
Am 18.12.2013 17:04, schrieb Antti Palosaari:
Quoted 2 lines
That same lock debug deadlock is still there (maybe ~4 times I report it during 2 years). Is that possible to fix easily at all?
Patches are always welcome. ;)
haha, I cannot simply learn every driver I meet some problems...

Quoted 8 lines

Hint:
If you report a bug ~4 times in 2 years but never get a reply, it usually means
a) nobody cares
b) nobody has the resources (time, knowledge) to fix it.
So you either have to live with this issue or to fix it yourself.

OK, as you request me to fix it, I will fix that by making DVB USB v2 driver for these em28xx devices I have added.

It should not be very much work as em28xx protocol is still relatively easy.

regards
Antti

Signature · 1 line

http://palosaari.fi/

Frank Schäfer

2013-12-22 18:01 UTC #5 lore raw

Am 22.12.2013 15:34, schrieb Antti Palosaari:

Quoted 21 lines · Frank Schäfer

Quoted 20 lines
Am 21.12.2013 20:55, schrieb Antti Palosaari:
Quoted 5 lines · Frank Schäfer
Quoted 4 lines
Hi Antti,
thank you for reporting this issue.
Quoted 7 lines
Quoted 5 lines
Am 18.12.2013 17:04, schrieb Antti Palosaari:
Quoted 2 lines
That same lock debug deadlock is still there (maybe ~4 times I report it during 2 years). Is that possible to fix easily at all?
Patches are always welcome. ;)
haha, I cannot simply learn every driver I meet some problems...
Hint:
If you report a bug ~4 times in 2 years but never get a reply, it usually means
a) nobody cares
b) nobody has the resources (time, knowledge) to fix it.

Quoted 7 lines

Quoted 1 line
So you either have to live with this issue or to fix it yourself.
OK, as you request me to fix it, I will fix that by making DVB USB v2 driver for these em28xx devices I have added.
It should not be very much work as em28xx protocol is still relatively easy.

How would that help to get those lockdep false warnings fixed ?
Btw: these warnings should appear for _all_ em28xx extensions (dvb, input, audio).

Regards,
Frank

Quoted 4 lines

regards
Antti

Antti Palosaari

author

2013-12-22 18:14 UTC #6 lore raw

Quoted 24 lines · Frank Schäfer

Am 22.12.2013 15:34, schrieb Antti Palosaari:
Quoted 23 lines · Frank Schäfer
Quoted 21 lines
Am 21.12.2013 20:55, schrieb Antti Palosaari:
Quoted 5 lines · Frank Schäfer
Quoted 4 lines
Hi Antti,
thank you for reporting this issue.
Quoted 7 lines
Quoted 5 lines
Am 18.12.2013 17:04, schrieb Antti Palosaari:
Quoted 2 lines
That same lock debug deadlock is still there (maybe ~4 times I report it during 2 years). Is that possible to fix easily at all?
Patches are always welcome. ;)
haha, I cannot simply learn every driver I meet some problems...
Hint:
If you report a bug ~4 times in 2 years but never get a reply, it usually means
a) nobody cares
b) nobody has the resources (time, knowledge) to fix it.
So you either have to live with this issue or to fix it yourself.

Quoted 8 lines

Quoted 5 lines
OK, as you request me to fix it, I will fix that by making DVB USB v2 driver for these em28xx devices I have added.
It should not be very much work as em28xx protocol is still relatively easy.
How would that help to get those lockdep false warnings fixed ?
Btw: these warnings should appear for _all_ em28xx extensions (dvb, input, audio).

I am already looking to silence that v4l2 lockdep report. It is hard to say how much it is work as I simply don't know even reasons.

I suspect that if I start learning and fixing em28xx driver it will take week or two as a workload. Writing new dvb-usb driver is only max 2 days of work and as a bonus you will get some missing features for free:
1) power-management
2) suspend/resume
3) PID filters

regards
Antti

Signature · 1 line

http://palosaari.fi/

Frank Schäfer

2013-12-22 18:50 UTC #7 lore raw

Am 22.12.2013 19:14, schrieb Antti Palosaari:

Quoted 38 lines · Frank Schäfer

Quoted 25 lines
Am 22.12.2013 15:34, schrieb Antti Palosaari:
Quoted 24 lines · Frank Schäfer
Quoted 22 lines
Am 21.12.2013 20:55, schrieb Antti Palosaari:
Quoted 5 lines · Frank Schäfer
Quoted 4 lines
Hi Antti,
thank you for reporting this issue.
Quoted 8 lines
Quoted 6 lines
Am 18.12.2013 17:04, schrieb Antti Palosaari:
Quoted 3 lines
That same lock debug deadlock is still there (maybe ~4 times I report
it during 2 years). Is that possible to fix easily at all?
Patches are always welcome. ;)
haha, I cannot simply learn every driver I meet some problems...
Hint:
If you report a bug ~4 times in 2 years but never get a reply, it usually means
a) nobody cares
b) nobody has the resources (time, knowledge) to fix it.
So you either have to live with this issue or to fix it yourself.
Quoted 8 lines
Quoted 5 lines
OK, as you request me to fix it, I will fix that by making DVB USB v2 driver for these em28xx devices I have added.
It should not be very much work as em28xx protocol is still relatively easy.
How would that help to get those lockdep false warnings fixed ?
Btw: these warnings should appear for _all_ em28xx extensions (dvb, input, audio).
I am already looking to silence that v4l2 lockdep report. It is hard to say how much it is work as I simply don't know even reasons.

Quoted 7 lines

I suspect that if I start learning and fixing em28xx driver it will take week or two as a workload. Writing new dvb-usb driver is only max 2 days of work and as a bonus you will get some missing features for free:
1) power-management
2) suspend/resume
3) PID filters

Sure, but we already have a driver for these devices.
I agree with you that em28xx is a big mess, but at least in this case it doesn't do anything wrong.
Does this false warning really make you so nervous that you're willing to spent 2 days for it ?
I appreciate that, but I suggest to spend these 2 days for fixing the issue instead of just avoiding it.

Regards,
Frank

Quoted 4 lines

regards
Antti

Mauro Carvalho Chehab

2013-12-22 14:53 UTC #8 lore raw

In reply to Frank Schäfer

Em Sun, 22 Dec 2013 14:51:53 +0100
Frank Schäfer <[email protected]> escreveu:

Quoted 13 lines

Am 21.12.2013 20:55, schrieb Antti Palosaari:
Quoted 5 lines · Frank Schäfer
Quoted 4 lines
Hi Antti,
thank you for reporting this issue.
Quoted 7 lines
Quoted 5 lines
Am 18.12.2013 17:04, schrieb Antti Palosaari:
Quoted 2 lines
That same lock debug deadlock is still there (maybe ~4 times I report it during 2 years). Is that possible to fix easily at all?
Patches are always welcome. ;)
haha, I cannot simply learn every driver I meet some problems...

Quoted 8 lines

Hint:
If you report a bug ~4 times in 2 years but never get a reply, it usually means
a) nobody cares
b) nobody has the resources (time, knowledge) to fix it.
So you either have to live with this issue or to fix it yourself.

It is the latter case: fixing it require lots of efforts.

One way to fix would be to change em28xx_close_extension() to something like:

drivers/media/usb/em28xx/em28xx-core.c +8 -2

index f6076a512e8f..d938e2bbd62f 100644
@@ -1350,13 +1350,19 @@ void em28xx_init_extension(struct em28xx *dev)
 
 void em28xx_close_extension(struct em28xx *dev)
 {
+	int (*fini)(struct em28xx *) = NULL;
 	const struct em28xx_ops *ops = NULL;
 
 	mutex_lock(&em28xx_devlist_mutex);
 	list_for_each_entry(ops, &em28xx_extension_devlist, next) {
-		if (ops->fini)
-			ops->fini(dev);
+		fini = ops->fini;
 	}
 	list_del(&dev->devlist);
 	mutex_unlock(&em28xx_devlist_mutex);
+
+	if (fini) {
+		mutex_lock(&dev->lock);
+		fini(dev);
+		mutex_unlock(&dev->lock);
+	}
 }

Please note that the above is not 100% correct, as one device may have more than one extension.

Then, it should be sure that on every place that em28xx_close_extension() is called, dev->lock is not taken.

As an alternative, eventually the extension list could be moved to the struct em28xx, but a device list is still needed, in order to handle extension module removal.

Another way that would probably be better is to convert the em28xx code that handles extension (extension here is dvb, rc, alsa) to use krefs, And add a kref free code that would call ops->fini. Note that, in this case, dev itself would also need to be a kref.

I suspect that using kref would would be cleaner, but a change like that would require to rewrite the extensions code.

Btw, there's a related RFC patchset that splits the V4L2 interface from em28xx, transforming it also into an extension. With such patch, a DVB only device should not call any v4l2 init code, nor require V4L2 to be enabled:

	https://patchwork.linuxtv.org/patch/17967/

The above RFC requires testing.

I may be able to find some time to do work on it this end of the year, starting with the V4L2 split patchset, depending if I finish some other things already on my todo list.

Regards,
Mauro

Signature · 2 lines

Cheers,
Mauro

Frank Schäfer

2013-12-22 18:10 UTC #9 lore raw

Am 22.12.2013 15:53, schrieb Mauro Carvalho Chehab:

Quoted 16 lines

Em Sun, 22 Dec 2013 14:51:53 +0100
Frank Schäfer <[email protected]> escreveu:
Quoted 13 lines
Am 21.12.2013 20:55, schrieb Antti Palosaari:
Quoted 10 lines · Frank Schäfer
Quoted 8 lines
Hi Antti,
thank you for reporting this issue.
Am 18.12.2013 17:04, schrieb Antti Palosaari:
Quoted 2 lines
That same lock debug deadlock is still there (maybe ~4 times I report it during 2 years). Is that possible to fix easily at all?
Patches are always welcome. ;)
haha, I cannot simply learn every driver I meet some problems...
Hint:

Quoted 7 lines

Quoted 6 lines
If you report a bug ~4 times in 2 years but never get a reply, it usually means
a) nobody cares
b) nobody has the resources (time, knowledge) to fix it.
So you either have to live with this issue or to fix it yourself.
It is the latter case: fixing it require lots of efforts.

Yes, I know. ;-)

Quoted 40 lines

One way to fix would be to change em28xx_close_extension() to something like:
drivers/media/usb/em28xx/em28xx-core.c +8 -2
index f6076a512e8f..d938e2bbd62f 100644
@@ -1350,13 +1350,19 @@ void em28xx_init_extension(struct em28xx *dev)
 
 void em28xx_close_extension(struct em28xx *dev)
 {
+	int (*fini)(struct em28xx *) = NULL;
 	const struct em28xx_ops *ops = NULL;
 
 	mutex_lock(&em28xx_devlist_mutex);
 	list_for_each_entry(ops, &em28xx_extension_devlist, next) {
-		if (ops->fini)
-			ops->fini(dev);
+		fini = ops->fini;
 	}
 	list_del(&dev->devlist);
 	mutex_unlock(&em28xx_devlist_mutex);
+
+	if (fini) {
+		mutex_lock(&dev->lock);
+		fini(dev);
+		mutex_unlock(&dev->lock);
+	}
 }
Please note that the above is not 100% correct, as one device may have more than one extension.
Then, it should be sure that on every place that em28xx_close_extension() is called, dev->lock is not taken.
As an alternative, eventually the extension list could be moved to the struct em28xx, but a device list is still needed, in order to handle extension module removal.

Quoted 7 lines

Another way that would probably be better is to convert the em28xx code that handles extension (extension here is dvb, rc, alsa) to use krefs, And add a kref free code that would call ops->fini. Note that, in this case, dev itself would also need to be a kref.
I suspect that using kref would would be cleaner, but a change like that would require to rewrite the extensions code.

I have zero knowledge about how the locking correctness stuff works, but what about improving it ?
Shouldn't it notice that flush_work() waits until the work is done before the lock is acquired ?

Quoted 5 lines

Btw, there's a related RFC patchset that splits the V4L2 interface from em28xx, transforming it also into an extension. With such patch, a DVB only device should not call any v4l2 init code, nor require V4L2 to be enabled:
	https://patchwork.linuxtv.org/patch/17967/ 

Yes, I remember it and it would be a big step forward.

Quoted 5 lines

The above RFC requires testing.
I may be able to find some time to do work on it this end of the year, starting with the V4L2 split patchset, depending if I finish some other things already on my todo list.

I'm going to review the patch within the next days and do some testing.

Regards,
Frank

Quoted 2 lines

Regards,
Mauro