Re: [PATCH 3/3] snd/hda: Protect concurrent display_power_status with a mutex

[Takashi Iwai <tiwai@suse.de>]

On Mon, 14 Jan 2019 18:51:31 +0100,
Chris Wilson wrote:
> 
> Quoting Takashi Iwai (2019-01-14 17:46:57)
> > On Mon, 14 Jan 2019 18:37:53 +0100,
> > Chris Wilson wrote:
> > > 
> > > Just in case the audio linkage is swapped between components during the
> > > runtime pm sequence, we need to protect the rpm tracking with a mutex.
> > 
> > It's not clear to me how does this happens.
> > Could you elaborate a bit more the scenario?
> 
> The code is written such that multiple bits within display_power_status
> can be set and cleared simultaneously. There was no serialisation
> mentioned in the routine, so I was fearful that the display_power_active
> here was being accessed concurrently -- and if that was explaining why
> snd/hda appears to be leaking the runtime pm (or at least is holding on
> to the wakeref longer than igt expects, > 10s).

Aha, and does patch actually "fix" the issue...?

It's a simple mutex addition, so no big show, and I'm fine with it,
but just wonder whether it really helped.


thanks,

Takashi