Re: [PATCH] Kernel crash

[Takashi Iwai <tiwai@suse.de>]

At Fri, 17 Sep 2004 12:22:07 +0200,
I wrote:
> 
> > The linking makes sense for hardware that support that. Otherwise, we can 
> > start streams in most close time, but draining and dropping doesn't make 
> > much sense, because different clocking sources for different cards will 
> > produce jitter, thus there is no real sync and application must care.
> 
> Agreed.  I've assumed that drain/drop are supposed to be synchronous,
> but they should not.

I just noticed that pcm_multi.c _assumes_ indeed that linked
draining/dropping works as synchronized.  So, the current semantics is
correct.

If snd_pcm_drain() affects only the given stream, then it's difficult
to get sync among all streams, because basically draining consists of
two phases:

 - trigger DRAIN state to all streams
 - wait until all streams get drained

We cannot do the procedure above in the serialized manner.


Also, another question is how to handle XRUN state.
When one of the linked streams gets XRUN, should all streams be
stopped and marked as XRUN?  I think yes.


Takashi


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