linux-kernel - Re: Context expectations in ALSA

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Date:   Thu, 22 Oct 2020 14:57:41 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Jaroslav Kysela <perex@...ex.cz>
Cc:     Takashi Iwai <tiwai@...e.com>, Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, Dom Cobley <dom@...pberrypi.com>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Subject: Re: Context expectations in ALSA

On Thu, Oct 22, 2020 at 12:03:19PM +0200, Jaroslav Kysela wrote:
> Dne 22. 10. 20 v 11:50 Maxime Ripard napsal(a):
> 
> > So, I'm not really sure what I'm supposed to do here. The drivers
> > involved don't appear to be doing anything extraordinary, but the issues
> > lockdep report are definitely valid too. What are the expectations in
> > terms of context from ALSA when running the callbacks, and how can we
> > fix it?
> 
> I think that you should set the non-atomic flag and wake up the workqueue or
> so from interrupt handler in this case. Call snd_pcm_period_elapsed() from the
> workqueue not the interrupt handler context.

Yeah, that was my first guess too. However, the DMA driver uses some
kind of generic helpers using a tasklet, so getting rid of it would take
some work and would very likely not be eligible for stable.

Maxime

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