Re: sound: deadlock involving snd_hrtimer_callback

From	Dmitry Vyukov <dvyukov@google.com>
Newsgroups	linux.kernel
Subject	Re: sound: deadlock involving snd_hrtimer_callback
Date	2016-04-24 17:20 +0200
Message-ID	<rrtZf-6Hu-5@gated-at.bofh.it> (permalink)
References	<rr66B-3Ns-9@gated-at.bofh.it> <rrcYq-1lD-51@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Sat, Apr 23, 2016 at 11:02 PM, Takashi Iwai <tiwai@suse.de> wrote:
> On Sat, 23 Apr 2016 15:40:21 +0200,
> Dmitry Vyukov wrote:
>>
>> Hi Takashi,
>>
>> I've incorporated your hrtimer fixes (but also updated to
>> ddce192106e4f984123884f8e878f66ace94b573) and now I am seeing lots of
>> the following deadlock messages:
>>
>>
>> [ INFO: possible circular locking dependency detected ]
>> 4.6.0-rc4+ #351 Not tainted
>> -------------------------------------------------------
>> swapper/0/0 is trying to acquire lock:
>>  (&(&timer->lock)->rlock){-.-...}, at: [<ffffffff8537a749>]
>> snd_timer_interrupt+0xa9/0xd30 sound/core/timer.c:701
>>
>> but task is already holding lock:
>>  (&(&stime->lock)->rlock){-.....}, at: [<ffffffff85383d3f>]
>> snd_hrtimer_callback+0x4f/0x2b0 sound/core/hrtimer.c:54
>>
>> which lock already depends on the new lock.
>
> Oh crap, my second patch is buggy, it leads to ABBA lock, indeed.
> The first patch is still OK, as it just adds a new behavior mode.
>
> Could you replace the second patch with the below one?


I've replaced the second path with this one. The deadlocks has gone,
but I've hit these two hangs that look related:

https://gist.githubusercontent.com/dvyukov/805718ea249c49d17ae759d1b0160684/raw/20891f7e87fe9af3967565559d465d296469244b/gistfile1.txt
https://gist.githubusercontent.com/dvyukov/7f397ea4aeb9e35596e0c8053cf35a11/raw/3fc22f24f7bab5941e47bab604f96487b5f1944d/gistfile1.txt

Thread

sound: deadlock involving snd_hrtimer_callback Dmitry Vyukov <dvyukov@google.com> - 2016-04-23 15:50 +0200
  Re: sound: deadlock involving snd_hrtimer_callback Takashi Iwai <tiwai@suse.de> - 2016-04-23 23:10 +0200
    Re: sound: deadlock involving snd_hrtimer_callback Dmitry Vyukov <dvyukov@google.com> - 2016-04-24 17:20 +0200
      Re: sound: deadlock involving snd_hrtimer_callback Dmitry Vyukov <dvyukov@google.com> - 2016-04-24 17:30 +0200
      Re: sound: deadlock involving snd_hrtimer_callback Takashi Iwai <tiwai@suse.de> - 2016-04-24 18:20 +0200
        Re: sound: deadlock involving snd_hrtimer_callback Dmitry Vyukov <dvyukov@google.com> - 2016-04-24 19:20 +0200
          Re: sound: deadlock involving snd_hrtimer_callback Takashi Iwai <tiwai@suse.de> - 2016-04-24 23:40 +0200
            Re: sound: deadlock involving snd_hrtimer_callback Dmitry Vyukov <dvyukov@google.com> - 2016-04-25 10:10 +0200
              Re: sound: deadlock involving snd_hrtimer_callback Takashi Iwai <tiwai@suse.de> - 2016-04-25 10:40 +0200

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