linux-kernel - Re: sound: deadlock between snd_rawmidi_kernel_open/snd_seq_port

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Message-ID: <s5h8u31hn49.wl-tiwai@suse.de>
Date:	Wed, 03 Feb 2016 15:41:58 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Dmitry Vyukov <dvyukov@...gle.com>
Cc:	alsa-devel@...a-project.org, Jie Yang <yang.jie@...el.com>,
	Mark Brown <broonie@...nel.org>,
	Jaroslav Kysela <perex@...ex.cz>,
	LKML <linux-kernel@...r.kernel.org>,
	Alexander Potapenko <glider@...gle.com>,
	Kostya Serebryany <kcc@...gle.com>,
	syzkaller <syzkaller@...glegroups.com>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: sound: deadlock between snd_rawmidi_kernel_open/snd_seq_port_connect

On Wed, 03 Feb 2016 14:22:18 +0100,
Dmitry Vyukov wrote:
> 
> On Wed, Feb 3, 2016 at 8:47 AM, Takashi Iwai <tiwai@...e.de> wrote:
> >> > This looks like a false-positive report to me.  Of course, we should
> >> > annotate the mutex there for nested locks, though.
> >>
> >>
> >> Takashi, can you please annotate it for lockdep? I hit it on every run.
> >
> > The lock had an annotation but alas it didn't seem enough.
> > In anyway, it's not good to have double locks if it's avoidable.  So I
> > worked on it now, and below is the current result of the hack.
> >
> > The change became a bit more intrusive than wished, but it should be
> > still simple enough.  I put this on top of topic/core-fixes branch.
> 
> 
> I don't see the deadlock reports now. Thanks!

Good to hear, now queued for the next pull request.
Thanks for quick tests!


Takashi