[alsa-devel] [PATCH] ASoC: Use codec mutex in dapm_set_pga()

Eero Nurkkala ext-eero.nurkkala at nokia.com
Thu Oct 1 13:01:09 CEST 2009

On Thu, 2009-10-01 at 12:37 +0200, ext Mark Brown wrote:
> On Thu, Oct 01, 2009 at 09:17:36AM +0300, ext-eero.nurkkala at nokia.com wrote:
> > From: Eero Nurkkala <ext-eero.nurkkala at nokia.com>
> > codec->mutex seems required if widget->* values
> > are altered. Moreover, snd_soc_dapm_put_volsw()
> > may alter widget->saved_value. dapm_set_pga()
> > uses widget->saved_value in a for loop which now
> > has a distant chance of getting out of control.
> Hrm.  This doesn't look right.  dapm_set_pga() is only called from
> within the DAPM power updates so we should've taken the codec mutex much
> further up the stack otherwise all the DAPM list walking and updating
> will have issues.  Was this just from code inspection or are you running
> into actual issues?

No, codex mutex is not taken further up the stack.
I ran lockdep for the case also. I also placed the mutexes
so that they're always taken in the same function.

I still think the described scenario can happen. Or could
you point where the mutex is taken earlier? If it was,
I would've deadlocked every time....Maybe I'm missing
some info.

BTW, what's the reasoning for codec mutex anyway?

(Yes, it was just code inspection).

- Eero

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