From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mailout4.w2.samsung.com ([211.189.100.14]:10694 "EHLO usmailout4.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751367AbaANT7O convert rfc822-to-8bit (ORCPT ); Tue, 14 Jan 2014 14:59:14 -0500 Received: from uscpsbgm2.samsung.com (u115.gpu85.samsung.co.kr [203.254.195.115]) by usmailout4.samsung.com (Oracle Communications Messaging Server 7u4-24.01(7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0MZE00629Q6O7070@usmailout4.samsung.com> for linux-media@vger.kernel.org; Tue, 14 Jan 2014 14:59:12 -0500 (EST) Date: Tue, 14 Jan 2014 17:59:07 -0200 From: Mauro Carvalho Chehab To: Frank =?UTF-8?B?U2Now6RmZXI=?= Cc: Linux Media Mailing List , Mauro Carvalho Chehab Subject: Re: [PATCH 5/7] em28xx-audio: remove a deplock circular dependency Message-id: <20140114175907.407c0d16@samsung.com> In-reply-to: <52D58569.3000405@googlemail.com> References: <1389567649-26838-1-git-send-email-m.chehab@samsung.com> <1389567649-26838-6-git-send-email-m.chehab@samsung.com> <52D45FC4.10106@googlemail.com> <20140114134541.1e1f2469@samsung.com> <52D58569.3000405@googlemail.com> MIME-version: 1.0 Content-type: text/plain; charset=UTF-8 Content-transfer-encoding: 8BIT Sender: linux-media-owner@vger.kernel.org List-ID: Em Tue, 14 Jan 2014 19:43:53 +0100 Frank Schäfer escreveu: > On 14.01.2014 16:45, Mauro Carvalho Chehab wrote: > > Em Mon, 13 Jan 2014 22:51:00 +0100 > > Frank Schäfer escreveu: > > > >> 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: [] snd_pcm_dev_disconnect+0x46/0x1e0 [snd_pcm] > >>> [ 322.026727] > >>> but task is already holding lock: > >>> [ 322.026767] (register_mutex#3){+.+.+.}, at: [] 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] [] __lock_acquire+0xb43/0x1330 > >>> [ 322.027401] [] lock_acquire+0xa2/0x120 > >>> [ 322.027479] [] mutex_lock_nested+0x5c/0x3c0 > >>> [ 322.027559] [] snd_pcm_dev_disconnect+0x24/0x1e0 [snd_pcm] > >>> [ 322.027642] [] snd_device_disconnect+0x6a/0xf0 [snd] > >>> [ 322.027727] [] snd_device_disconnect_all+0x4c/0x90 [snd] > >>> [ 322.027814] [] snd_card_disconnect+0x126/0x1d0 [snd] > >>> [ 322.027898] [] snd_card_free+0x18/0x90 [snd] > >>> [ 322.027982] [] em28xx_audio_fini+0x8f/0xa0 [em28xx_alsa] > >>> [ 322.028063] [] em28xx_close_extension+0x56/0x90 [em28xx] > >>> [ 322.028143] [] em28xx_usb_disconnect+0x79/0x90 [em28xx] > >>> [ 322.028222] [] usb_unbind_interface+0x67/0x1d0 > >>> [ 322.028302] [] __device_release_driver+0x7f/0xf0 > >>> [ 322.028381] [] device_release_driver+0x25/0x40 > >>> [ 322.028462] [] bus_remove_device+0x11c/0x1a0 > >>> [ 322.028540] [] device_del+0x136/0x1d0 > >>> [ 322.028619] [] usb_disable_device+0xb0/0x290 > >>> [ 322.028698] [] usb_disconnect+0xb5/0x1d0 > >>> [ 322.028779] [] hub_port_connect_change+0xd6/0xad0 > >>> [ 322.028859] [] hub_events+0x313/0x9b0 > >>> [ 322.028940] [] hub_thread+0x35/0x170 > >>> [ 322.029019] [] kthread+0xff/0x120 > >>> [ 322.029099] [] ret_from_fork+0x7c/0xb0 > >>> [ 322.029179] > >>> -> #1 (&dev->lock#2){+.+.+.}: > >>> [ 322.029414] [] __lock_acquire+0xb43/0x1330 > >>> [ 322.029494] [] lock_acquire+0xa2/0x120 > >>> [ 322.029572] [] mutex_lock_nested+0x5c/0x3c0 > >>> [ 322.029651] [] snd_em28xx_pcm_close+0x3e/0x100 [em28xx_alsa] > >>> [ 322.029732] [] snd_pcm_release_substream.part.29+0x3f/0x90 [snd_pcm] > >>> [ 322.029816] [] snd_pcm_release+0xb0/0xd0 [snd_pcm] > >>> [ 322.029900] [] __fput+0xe2/0x230 > >>> [ 322.029979] [] ____fput+0xe/0x10 > >>> [ 322.030057] [] task_work_run+0x9f/0xe0 > >>> [ 322.030135] [] do_notify_resume+0x61/0xa0 > >>> [ 322.030223] [] int_signal+0x12/0x17 > >>> [ 322.030294] > >>> -> #0 (&pcm->open_mutex){+.+.+.}: > >>> [ 322.030473] [] check_prevs_add+0x947/0x950 > >>> [ 322.030546] [] __lock_acquire+0xb43/0x1330 > >>> [ 322.030618] [] lock_acquire+0xa2/0x120 > >>> [ 322.030689] [] mutex_lock_nested+0x5c/0x3c0 > >>> [ 322.030760] [] snd_pcm_dev_disconnect+0x46/0x1e0 [snd_pcm] > >>> [ 322.030835] [] snd_device_disconnect+0x6a/0xf0 [snd] > >>> [ 322.030913] [] snd_device_disconnect_all+0x4c/0x90 [snd] > >>> [ 322.030988] [] snd_card_disconnect+0x126/0x1d0 [snd] > >>> [ 322.031067] [] snd_card_free+0x18/0x90 [snd] > >>> [ 322.031146] [] em28xx_audio_fini+0x8f/0xa0 [em28xx_alsa] > >>> [ 322.031220] [] em28xx_close_extension+0x56/0x90 [em28xx] > >>> [ 322.031292] [] em28xx_usb_disconnect+0x79/0x90 [em28xx] > >>> [ 322.031363] [] usb_unbind_interface+0x67/0x1d0 > >>> [ 322.031433] [] __device_release_driver+0x7f/0xf0 > >>> [ 322.031503] [] device_release_driver+0x25/0x40 > >>> [ 322.031573] [] bus_remove_device+0x11c/0x1a0 > >>> [ 322.031643] [] device_del+0x136/0x1d0 > >>> [ 322.031714] [] usb_disable_device+0xb0/0x290 > >>> [ 322.031784] [] usb_disconnect+0xb5/0x1d0 > >>> [ 322.031853] [] hub_port_connect_change+0xd6/0xad0 > >>> [ 322.031922] [] hub_events+0x313/0x9b0 > >>> [ 322.031992] [] hub_thread+0x35/0x170 > >>> [ 322.032062] [] kthread+0xff/0x120 > >>> [ 322.032135] [] 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 *** > I don't get it. Where is the deadlock here ??? > Mauro, be honest: did you understand what's going on here ? > > >>> > >>> [ 322.033204] 6 locks held by khubd/54: > >>> [ 322.033239] #0: (&__lockdep_no_validate__){......}, at: [] hub_events+0xb4/0x9b0 > >>> [ 322.033446] #1: (&__lockdep_no_validate__){......}, at: [] usb_disconnect+0x66/0x1d0 > >>> [ 322.033655] #2: (&__lockdep_no_validate__){......}, at: [] device_release_driver+0x1d/0x40 > >>> [ 322.033859] #3: (em28xx_devlist_mutex){+.+.+.}, at: [] em28xx_close_extension+0x27/0x90 [em28xx] > >>> [ 322.034067] #4: (&dev->lock#2){+.+.+.}, at: [] em28xx_close_extension+0x31/0x90 [em28xx] > >>> [ 322.034307] #5: (register_mutex#3){+.+.+.}, at: [] 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] [] dump_stack+0x45/0x56 > >>> [ 322.035276] [] print_circular_bug+0x200/0x20e > >>> [ 322.035320] [] check_prevs_add+0x947/0x950 > >>> [ 322.035365] [] ? native_sched_clock+0x13/0x80 > >>> [ 322.035409] [] __lock_acquire+0xb43/0x1330 > >>> [ 322.035454] [] lock_acquire+0xa2/0x120 > >>> [ 322.035500] [] ? snd_pcm_dev_disconnect+0x46/0x1e0 [snd_pcm] > >>> [ 322.035550] [] mutex_lock_nested+0x5c/0x3c0 > >>> [ 322.035596] [] ? snd_pcm_dev_disconnect+0x46/0x1e0 [snd_pcm] > >>> [ 322.035648] [] ? snd_pcm_dev_disconnect+0x46/0x1e0 [snd_pcm] > >>> [ 322.035697] [] ? trace_hardirqs_on_caller+0x105/0x1d0 > >>> [ 322.035744] [] snd_pcm_dev_disconnect+0x46/0x1e0 [snd_pcm] > >>> [ 322.035797] [] snd_device_disconnect+0x6a/0xf0 [snd] > >>> [ 322.035852] [] snd_device_disconnect_all+0x4c/0x90 [snd] > >>> [ 322.035904] [] snd_card_disconnect+0x126/0x1d0 [snd] > >>> [ 322.035957] [] snd_card_free+0x18/0x90 [snd] > >>> [ 322.036008] [] em28xx_audio_fini+0x8f/0xa0 [em28xx_alsa] > >>> [ 322.036054] [] em28xx_close_extension+0x56/0x90 [em28xx] > >>> [ 322.036100] [] em28xx_usb_disconnect+0x79/0x90 [em28xx] > >>> [ 322.036144] [] usb_unbind_interface+0x67/0x1d0 > >>> [ 322.036188] [] __device_release_driver+0x7f/0xf0 > >>> [ 322.036231] [] device_release_driver+0x25/0x40 > >>> [ 322.036274] [] bus_remove_device+0x11c/0x1a0 > >>> [ 322.036318] [] device_del+0x136/0x1d0 > >>> [ 322.036361] [] usb_disable_device+0xb0/0x290 > >>> [ 322.036404] [] usb_disconnect+0xb5/0x1d0 > >>> [ 322.036447] [] hub_port_connect_change+0xd6/0xad0 > >>> [ 322.036492] [] ? usb_control_msg+0xd4/0x110 > >>> [ 322.036535] [] hub_events+0x313/0x9b0 > >>> [ 322.036579] [] ? trace_hardirqs_on_caller+0x105/0x1d0 > >>> [ 322.036623] [] hub_thread+0x35/0x170 > >>> [ 322.036667] [] ? abort_exclusive_wait+0xb0/0xb0 > >>> [ 322.036711] [] ? hub_events+0x9b0/0x9b0 > >>> [ 322.036756] [] kthread+0xff/0x120 > >>> [ 322.036802] [] ? kthread_create_on_node+0x250/0x250 > >>> [ 322.036846] [] ret_from_fork+0x7c/0xb0 > >>> [ 322.036890] [] ? kthread_create_on_node+0x250/0x250 > >>> > >>> Signed-off-by: Mauro Carvalho Chehab > >>> --- > >>> 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); > >>> + } > >>> } > >>> } > After thinking about this for a while: > Does your patch > > [PATCH] em28xx: push mutex down to extensions on .fini callback > > which you've sent afterwards fix this warning, too ? Yes, the above patch fixed the circular lock issues. I dropped this patch. The only patch pending to be applied on this series is patch 4. -- Cheers, Mauro