Re: [GIT PULL] sound updates for 5.14-rc1

From: Takashi Sakamoto
Date: Sat Jul 03 2021 - 02:39:01 EST


On Fri, Jul 02, 2021 at 10:19:46PM -0700, Linus Torvalds wrote:
> On Fri, Jul 2, 2021 at 9:37 PM Linus Torvalds
> <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > But I thought I'd report this as a likely candidate.
> Confirmed. The watchdog hang bisects right down to commit 9ce650a75a3b
> ("ALSA: usb-audio: Reduce latency at playback start").
> And reverting it on top of my tree also fixes the hang, so it's not
> some bisection fluke.
> I have no idea what is actually wrong with that commit, but it most
> definitely is the problem, and I have reverted it in my tree so that I
> can continue merging stuff tomorrow.

The cause seems to be the attempt to lock PCM substream recursively
introduced by the issued commit.

Would I ask you to test with below patch? I apologize that the patch is
still untested in my side since at present I have no preparation to debug
USB stuffs instantly (I'm just a maintainer for ALSA firewire stack...),
so I'm glad if getting your cooperation for the issue.

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