sound/pcm/* bugs (was: Re: page fault panic tracked down (selwakeuppri()) - really sound/pcm/*)

Stefan Ehmann shoesoft at
Fri Jan 16 11:52:08 PST 2004

On Fri, 2004-01-16 at 10:31, Don Lewis wrote:
> On 15 Jan, Stefan Ehmann wrote:
> > This time the system survived sysctl but as soon as sound playback
> > starts the assertion in channel.c:978 gets triggered.
> > 
> > Looks like setting up sound would be a good idea since there are
> > probably more traps ahead.
> Judging by all the arrows I just dug out of my back, I'd say you are
> correct.  Really enabling the lock assertion checks turned up quite a
> few things, and I found some more locking problems by inspection.
> The following patch seems to be at least somewhat stable on my machine.
> I did get one last panic in feed_vchan_s16() that I haven't been able to
> reproduce since I added some more sanity checks. Since it was caught in
> the interrupt routine, it's not easy to track down to its root cause.  I
> think there is still a bug somewhere, but it's not easy to trigger.

Good news: no panic so far.

Bad news: sound stopped working after some time (Chances are that the
system would have panicked on the unpatched kernel at the same time)

/dev/dsp: Operation not supported by device

I'm not sure why this happened.

I tried to increase vchans to 5 and got this on printed
cnt 4, newcnt 1, busy 2

However, I get same message when I try to play anything.

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