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From: Maciej Rutecki <maciej.rutecki@gmail.com>
Reply-To: maciej.rutecki@gmail.com
To: Josh Boyer <jwboyer@redhat.com>
Subject: Re: 3.3-rc2 snd_pcm lockdep backtrace
Date: Wed, 8 Feb 2012 18:54:08 +0100
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Cc: Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.de>,
        alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
        kernel-team@fedoraproject.org
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On poniedziałek, 6 lutego 2012 o 15:56:22 Josh Boyer wrote:
> Hi All,
> 
> We've had a report[1] of a lockdep backtrace from the snd_pcm driver.  I
> was wondering if anyone had hit this already or had some decent ideas on
> what the issue might be.
> 
> josh
> 
> [1] https://bugzilla.redhat.com/show_bug.cgi?id=787319
> 
> backtrace:
> :[ INFO: possible recursive locking detected ]
> :3.3.0-0.rc2.git2.1.fc17.x86_64 #1 Not tainted
> :---------------------------------------------
> :
> :pulseaudio/954 is trying to acquire lock:
> : (&(&substream->self_group.lock)->rlock/1){......}, at:
> : [<ffffffffa00d9093>]
> 
> snd_pcm_action_group+0xa3/0x240 [snd_pcm]
> 
> :but task is already holding lock:
> : (&(&substream->self_group.lock)->rlock/1){......}, at:
> : [<ffffffffa00d9093>]
> 
> snd_pcm_action_group+0xa3/0x240 [snd_pcm]
> 
> :other info that might help us debug this:
> : Possible unsafe locking scenario:
> :       CPU0
> :       ----
> :  
> :  lock(&(&substream->self_group.lock)->rlock/1);
> :  lock(&(&substream->self_group.lock)->rlock/1);
> : 
> : *** DEADLOCK ***
> : May be due to missing lock nesting notation
> :
> :4 locks held by pulseaudio/954:
> : #0:  (snd_pcm_link_rwlock){......}, at: [<ffffffffa00d9e62>]
> 
> snd_pcm_drop+0x62/0x110 [snd_pcm]
> 
> : #1:  (&(&substream->self_group.lock)->rlock){......}, at:
> [<ffffffffa00d9e6a>] snd_pcm_drop+0x6a/0x110 [snd_pcm]
> 
> : #2:  (&(&substream->group->lock)->rlock){......}, at:
> : [<ffffffffa00d93ce>]
> 
> snd_pcm_action+0x3e/0xb0 [snd_pcm]
> 
> : #3:  (&(&substream->self_group.lock)->rlock/1){......}, at:
> [<ffffffffa00d9093>] snd_pcm_action_group+0xa3/0x240 [snd_pcm]
> 
> :stack backtrace:
> :Pid: 954, comm: pulseaudio Not tainted 3.3.0-0.rc2.git2.1.fc17.x86_64 #1
> :
> :Call Trace:
> : [<ffffffff810cb7ec>] __lock_acquire+0x160c/0x1ad0
> : [<ffffffff810ca4f6>] ? __lock_acquire+0x316/0x1ad0
> : [<ffffffff81020f99>] ? sched_clock+0x9/0x10
> : [<ffffffff810a24a5>] ? sched_clock_local+0x25/0xa0
> : [<ffffffff810cc381>] lock_acquire+0xa1/0x1e0
> : [<ffffffffa00d9093>] ? snd_pcm_action_group+0xa3/0x240 [snd_pcm]
> : [<ffffffff8169cca4>] _raw_spin_lock_nested+0x44/0x80
> : [<ffffffffa00d9093>] ? snd_pcm_action_group+0xa3/0x240 [snd_pcm]
> : [<ffffffffa00d9093>] snd_pcm_action_group+0xa3/0x240 [snd_pcm]
> : [<ffffffffa00d9401>] snd_pcm_action+0x71/0xb0 [snd_pcm]
> : [<ffffffffa00d945a>] snd_pcm_stop+0x1a/0x20 [snd_pcm]
> : [<ffffffffa00d9e84>] snd_pcm_drop+0x84/0x110 [snd_pcm]
> : [<ffffffffa00dbba8>] snd_pcm_common_ioctl1+0x4a8/0xbe0 [snd_pcm]
> : [<ffffffffa00dc650>] snd_pcm_playback_ioctl1+0x60/0x2d0 [snd_pcm]
> : [<ffffffff812c1481>] ? file_has_perm+0xe1/0xf0
> : [<ffffffffa00dc8f4>] snd_pcm_playback_ioctl+0x34/0x40 [snd_pcm]
> : [<ffffffff811cf8d9>] do_vfs_ioctl+0x99/0x5a0
> : [<ffffffff811cfe79>] sys_ioctl+0x99/0xa0
> : [<ffffffff816a63e9>] system_call_fastpath+0x16/0x1b
> 

I created a Bugzilla entry at 
https://bugzilla.kernel.org/show_bug.cgi?id=42746
for your bug report, please add your address to the CC list in there, thanks!

-- 
Maciej Rutecki
http://www.mrutecki.pl
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