[alsa-devel] [PATCH] [RFC] sis7019: Initial support for the SiS7019 Audio Accelerator

[Dave Dillow]

On Tue, 2007-10-09 at 11:48 +0200, Takashi Iwai wrote:
> You need to unlock sis->hw_lock before calling
> snd_pcm_period_elapsed().  It may call snd_pcm_stop() at XRUN, and
> this invokes the trigger callback, which locks hw_lock again.
> Simply re-acquire hw_lock after calling snd_pcm_period_elapsed().

If I'm guaranteed that I'll never have my prepare() method called
concurrently for the same substream, I think I can do away with the
hw_lock completely -- though I need to think through scenarios about
closing the stream and a late interrupt...

It looks like my prepare() gets called by snd_pcm_action_nonatomic() in
sound/core/pcm_native.c, and that takes a read lock on the link
semaphore, so the group won't be changed, but I don't see anything that
would prevent prepare() being called twice on the same substream
concurrently. So, I'll probably need to keep some locking to avoid an
issue there, unless I'm missing a lock upstream.

I'll have a look at removing locks from the interrupt handler
completely, though.

Thanks,
Dave