Am 13.01.2014 00:00, schrieb Mauro Carvalho Chehab:
> We can't lock at pcm close, as it causes circular dependency
> lock issues with .init and .fini callbacks. So, move the code
> that puts the device on mute to the kthread.
>
> [ 322.026316] ======================================================
> [ 322.026356] [ INFO: possible circular locking dependency detected ]
> [ 322.026397] 3.13.0-rc1+ #24 Not tainted
> [ 322.026437] -------------------------------------------------------
> [ 322.026476] khubd/54 is trying to acquire lock:
> [ 322.026516] (&pcm->open_mutex){+.+.+.}, at: [<ffffffffa04819e6>] snd_pcm_dev_disconnect+0x46/0x1e0 [snd_pcm]
> [ 322.026727]
> but task is already holding lock:
> [ 322.026767] (register_mutex#3){+.+.+.}, at: [<ffffffffa04819c4>] snd_pcm_dev_disconnect+0x24/0x1e0 [snd_pcm]
> [ 322.027005]
> which lock already depends on the new lock.
>
> [ 322.027045]
> the existing dependency chain (in reverse order) is:
> [ 322.027084]
> -> #2 (register_mutex#3){+.+.+.}:
> [ 322.027318] [<ffffffff810b8fa3>] __lock_acquire+0xb43/0x1330
> [ 322.027401] [<ffffffff810b9f82>] lock_acquire+0xa2/0x120
> [ 322.027479] [<ffffffff816a5b6c>] mutex_lock_nested+0x5c/0x3c0
> [ 322.027559] [<ffffffffa04819c4>] snd_pcm_dev_disconnect+0x24/0x1e0 [snd_pcm]
> [ 322.027642] [<ffffffffa02e855a>] snd_device_disconnect+0x6a/0xf0 [snd]
> [ 322.027727] [<ffffffffa02e86ac>] snd_device_disconnect_all+0x4c/0x90 [snd]
> [ 322.027814] [<ffffffffa02e1876>] snd_card_disconnect+0x126/0x1d0 [snd]
> [ 322.027898] [<ffffffffa02e1ea8>] snd_card_free+0x18/0x90 [snd]
> [ 322.027982] [<ffffffffa087235f>] em28xx_audio_fini+0x8f/0xa0 [em28xx_alsa]
> [ 322.028063] [<ffffffffa085cba6>] em28xx_close_extension+0x56/0x90 [em28xx]
> [ 322.028143] [<ffffffffa085e639>] em28xx_usb_disconnect+0x79/0x90 [em28xx]
> [ 322.028222] [<ffffffff814a06e7>] usb_unbind_interface+0x67/0x1d0
> [ 322.028302] [<ffffffff8142920f>] __device_release_driver+0x7f/0xf0
> [ 322.028381] [<ffffffff814292a5>] device_release_driver+0x25/0x40
> [ 322.028462] [<ffffffff81428b0c>] bus_remove_device+0x11c/0x1a0
> [ 322.028540] [<ffffffff81425536>] device_del+0x136/0x1d0
> [ 322.028619] [<ffffffff8149e0c0>] usb_disable_device+0xb0/0x290
> [ 322.028698] [<ffffffff814930c5>] usb_disconnect+0xb5/0x1d0
> [ 322.028779] [<ffffffff81495ab6>] hub_port_connect_change+0xd6/0xad0
> [ 322.028859] [<ffffffff814967c3>] hub_events+0x313/0x9b0
> [ 322.028940] [<ffffffff81496e95>] hub_thread+0x35/0x170
> [ 322.029019] [<ffffffff8108ea2f>] kthread+0xff/0x120
> [ 322.029099] [<ffffffff816b187c>] ret_from_fork+0x7c/0xb0
> [ 322.029179]
> -> #1 (&dev->lock#2){+.+.+.}:
> [ 322.029414] [<ffffffff810b8fa3>] __lock_acquire+0xb43/0x1330
> [ 322.029494] [<ffffffff810b9f82>] lock_acquire+0xa2/0x120
> [ 322.029572] [<ffffffff816a5b6c>] mutex_lock_nested+0x5c/0x3c0
> [ 322.029651] [<ffffffffa087122e>] snd_em28xx_pcm_close+0x3e/0x100 [em28xx_alsa]
> [ 322.029732] [<ffffffffa048620f>] snd_pcm_release_substream.part.29+0x3f/0x90 [snd_pcm]
> [ 322.029816] [<ffffffffa0486340>] snd_pcm_release+0xb0/0xd0 [snd_pcm]
> [ 322.029900] [<ffffffff811c9752>] __fput+0xe2/0x230
> [ 322.029979] [<ffffffff811c98ee>] ____fput+0xe/0x10
> [ 322.030057] [<ffffffff8108b64f>] task_work_run+0x9f/0xe0
> [ 322.030135] [<ffffffff81013a81>] do_notify_resume+0x61/0xa0
> [ 322.030223] [<ffffffff816b1c62>] int_signal+0x12/0x17
> [ 322.030294]
> -> #0 (&pcm->open_mutex){+.+.+.}:
> [ 322.030473] [<ffffffff810b7a47>] check_prevs_add+0x947/0x950
> [ 322.030546] [<ffffffff810b8fa3>] __lock_acquire+0xb43/0x1330
> [ 322.030618] [<ffffffff810b9f82>] lock_acquire+0xa2/0x120
> [ 322.030689] [<ffffffff816a5b6c>] mutex_lock_nested+0x5c/0x3c0
> [ 322.030760] [<ffffffffa04819e6>] snd_pcm_dev_disconnect+0x46/0x1e0 [snd_pcm]
> [ 322.030835] [<ffffffffa02e855a>] snd_device_disconnect+0x6a/0xf0 [snd]
> [ 322.030913] [<ffffffffa02e86ac>] snd_device_disconnect_all+0x4c/0x90 [snd]
> [ 322.030988] [<ffffffffa02e1876>] snd_card_disconnect+0x126/0x1d0 [snd]
> [ 322.031067] [<ffffffffa02e1ea8>] snd_card_free+0x18/0x90 [snd]
> [ 322.031146] [<ffffffffa087235f>] em28xx_audio_fini+0x8f/0xa0 [em28xx_alsa]
> [ 322.031220] [<ffffffffa085cba6>] em28xx_close_extension+0x56/0x90 [em28xx]
> [ 322.031292] [<ffffffffa085e639>] em28xx_usb_disconnect+0x79/0x90 [em28xx]
> [ 322.031363] [<ffffffff814a06e7>] usb_unbind_interface+0x67/0x1d0
> [ 322.031433] [<ffffffff8142920f>] __device_release_driver+0x7f/0xf0
> [ 322.031503] [<ffffffff814292a5>] device_release_driver+0x25/0x40
> [ 322.031573] [<ffffffff81428b0c>] bus_remove_device+0x11c/0x1a0
> [ 322.031643] [<ffffffff81425536>] device_del+0x136/0x1d0
> [ 322.031714] [<ffffffff8149e0c0>] usb_disable_device+0xb0/0x290
> [ 322.031784] [<ffffffff814930c5>] usb_disconnect+0xb5/0x1d0
> [ 322.031853] [<ffffffff81495ab6>] hub_port_connect_change+0xd6/0xad0
> [ 322.031922] [<ffffffff814967c3>] hub_events+0x313/0x9b0
> [ 322.031992] [<ffffffff81496e95>] hub_thread+0x35/0x170
> [ 322.032062] [<ffffffff8108ea2f>] kthread+0xff/0x120
> [ 322.032135] [<ffffffff816b187c>] ret_from_fork+0x7c/0xb0
> [ 322.032205]
> other info that might help us debug this:
>
> [ 322.032240] Chain exists of:
> &pcm->open_mutex --> &dev->lock#2 --> register_mutex#3
>
> [ 322.032547] Possible unsafe locking scenario:
>
> [ 322.032582] CPU0 CPU1
> [ 322.032616] ---- ----
> [ 322.032654] lock(register_mutex#3);
> [ 322.032793] lock(&dev->lock#2);
> [ 322.032929] lock(register_mutex#3);
> [ 322.033064] lock(&pcm->open_mutex);
> [ 322.033168]
> *** DEADLOCK ***
>
> [ 322.033204] 6 locks held by khubd/54:
> [ 322.033239] #0: (&__lockdep_no_validate__){......}, at: [<ffffffff81496564>] hub_events+0xb4/0x9b0
> [ 322.033446] #1: (&__lockdep_no_validate__){......}, at: [<ffffffff81493076>] usb_disconnect+0x66/0x1d0
> [ 322.033655] #2: (&__lockdep_no_validate__){......}, at: [<ffffffff8142929d>] device_release_driver+0x1d/0x40
> [ 322.033859] #3: (em28xx_devlist_mutex){+.+.+.}, at: [<ffffffffa085cb77>] em28xx_close_extension+0x27/0x90 [em28xx]
> [ 322.034067] #4: (&dev->lock#2){+.+.+.}, at: [<ffffffffa085cb81>] em28xx_close_extension+0x31/0x90 [em28xx]
> [ 322.034307] #5: (register_mutex#3){+.+.+.}, at: [<ffffffffa04819c4>] snd_pcm_dev_disconnect+0x24/0x1e0 [snd_pcm]
> [ 322.034552]
> stack backtrace:
> [ 322.034588] CPU: 3 PID: 54 Comm: khubd Not tainted 3.13.0-rc1+ #24
> [ 322.034624] Hardware name: SAMSUNG ELECTRONICS CO., LTD. 550P5C/550P7C/SAMSUNG_NP1234567890, BIOS P04ABI.013.130220.dg 02/20/2013
> [ 322.034659] ffffffff82513770 ffff880221bcd7c8 ffffffff816a03c6 ffffffff8250a810
> [ 322.034832] ffff880221bcd808 ffffffff8169a203 ffff880221bcd830 0000000000000005
> [ 322.035004] ffff8802222b2880 ffff8802222b3020 ffff8802222b3020 0000000000000006
> [ 322.035187] Call Trace:
> [ 322.035230] [<ffffffff816a03c6>] dump_stack+0x45/0x56
> [ 322.035276] [<ffffffff8169a203>] print_circular_bug+0x200/0x20e
> [ 322.035320] [<ffffffff810b7a47>] check_prevs_add+0x947/0x950
> [ 322.035365] [<ffffffff8101b303>] ? native_sched_clock+0x13/0x80
> [ 322.035409] [<ffffffff810b8fa3>] __lock_acquire+0xb43/0x1330
> [ 322.035454] [<ffffffff810b9f82>] lock_acquire+0xa2/0x120
> [ 322.035500] [<ffffffffa04819e6>] ? snd_pcm_dev_disconnect+0x46/0x1e0 [snd_pcm]
> [ 322.035550] [<ffffffff816a5b6c>] mutex_lock_nested+0x5c/0x3c0
> [ 322.035596] [<ffffffffa04819e6>] ? snd_pcm_dev_disconnect+0x46/0x1e0 [snd_pcm]
> [ 322.035648] [<ffffffffa04819e6>] ? snd_pcm_dev_disconnect+0x46/0x1e0 [snd_pcm]
> [ 322.035697] [<ffffffff810b8045>] ? trace_hardirqs_on_caller+0x105/0x1d0
> [ 322.035744] [<ffffffffa04819e6>] snd_pcm_dev_disconnect+0x46/0x1e0 [snd_pcm]
> [ 322.035797] [<ffffffffa02e855a>] snd_device_disconnect+0x6a/0xf0 [snd]
> [ 322.035852] [<ffffffffa02e86ac>] snd_device_disconnect_all+0x4c/0x90 [snd]
> [ 322.035904] [<ffffffffa02e1876>] snd_card_disconnect+0x126/0x1d0 [snd]
> [ 322.035957] [<ffffffffa02e1ea8>] snd_card_free+0x18/0x90 [snd]
> [ 322.036008] [<ffffffffa087235f>] em28xx_audio_fini+0x8f/0xa0 [em28xx_alsa]
> [ 322.036054] [<ffffffffa085cba6>] em28xx_close_extension+0x56/0x90 [em28xx]
> [ 322.036100] [<ffffffffa085e639>] em28xx_usb_disconnect+0x79/0x90 [em28xx]
> [ 322.036144] [<ffffffff814a06e7>] usb_unbind_interface+0x67/0x1d0
> [ 322.036188] [<ffffffff8142920f>] __device_release_driver+0x7f/0xf0
> [ 322.036231] [<ffffffff814292a5>] device_release_driver+0x25/0x40
> [ 322.036274] [<ffffffff81428b0c>] bus_remove_device+0x11c/0x1a0
> [ 322.036318] [<ffffffff81425536>] device_del+0x136/0x1d0
> [ 322.036361] [<ffffffff8149e0c0>] usb_disable_device+0xb0/0x290
> [ 322.036404] [<ffffffff814930c5>] usb_disconnect+0xb5/0x1d0
> [ 322.036447] [<ffffffff81495ab6>] hub_port_connect_change+0xd6/0xad0
> [ 322.036492] [<ffffffff8149cb04>] ? usb_control_msg+0xd4/0x110
> [ 322.036535] [<ffffffff814967c3>] hub_events+0x313/0x9b0
> [ 322.036579] [<ffffffff810b8045>] ? trace_hardirqs_on_caller+0x105/0x1d0
> [ 322.036623] [<ffffffff81496e95>] hub_thread+0x35/0x170
> [ 322.036667] [<ffffffff810af310>] ? abort_exclusive_wait+0xb0/0xb0
> [ 322.036711] [<ffffffff81496e60>] ? hub_events+0x9b0/0x9b0
> [ 322.036756] [<ffffffff8108ea2f>] kthread+0xff/0x120
> [ 322.036802] [<ffffffff8108e930>] ? kthread_create_on_node+0x250/0x250
> [ 322.036846] [<ffffffff816b187c>] ret_from_fork+0x7c/0xb0
> [ 322.036890] [<ffffffff8108e930>] ? kthread_create_on_node+0x250/0x250
>
> Signed-off-by: Mauro Carvalho Chehab <m.chehab@xxxxxxxxxxx>
> ---
> drivers/media/usb/em28xx/em28xx-audio.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/usb/em28xx/em28xx-audio.c b/drivers/media/usb/em28xx/em28xx-audio.c
> index cdc2fcf3e05e..5e16fcf18cac 100644
> --- a/drivers/media/usb/em28xx/em28xx-audio.c
> +++ b/drivers/media/usb/em28xx/em28xx-audio.c
> @@ -311,20 +311,17 @@ static int snd_em28xx_pcm_close(struct snd_pcm_substream *substream)
> dprintk("closing device\n");
>
> dev->mute = 1;
> - mutex_lock(&dev->lock);
> dev->adev.users--;
> if (atomic_read(&dev->stream_started) > 0) {
> atomic_set(&dev->stream_started, 0);
> schedule_work(&dev->wq_trigger);
> }
>
> - em28xx_audio_analog_set(dev);
> if (substream->runtime->dma_area) {
> dprintk("freeing\n");
> vfree(substream->runtime->dma_area);
> substream->runtime->dma_area = NULL;
> }
> - mutex_unlock(&dev->lock);
>
> return 0;
> }
> @@ -395,6 +392,13 @@ static void audio_trigger(struct work_struct *work)
> } else {
> dprintk("stopping capture");
> em28xx_deinit_isoc_audio(dev);
> +
> + /* Mute device if needed */
> + if (dev->mute) {
> + mutex_lock(&dev->lock);
> + em28xx_audio_analog_set(dev);
> + mutex_unlock(&dev->lock);
> + }
> }
> }
It's already late and I don't understand this deadlock yet completely,
but are you sure this is the proper fix for this issue ?
What happens when capturing is restarted ? Shouldn't the device then be
unmuted again ?
How often does the start/stop/resume happen ?
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