PERFORCE change 113164 for review

[Hans Petter Selasky]

On Friday 19 January 2007 17:58, Attilio Rao wrote:
> 2007/1/19, Hans Petter Selasky <hselasky at freebsd.org>:
> > http://perforce.freebsd.org/chv.cgi?CH=113164
> >
> > Change 113164 by hselasky at hselasky_mini_itx on 2007/01/19 16:56:15
> >
> >         The sound mutex needs to allow recursion, else the
> >         new "uaudio" will not work.
> >
> > Affected files ...
> >
> > .. //depot/projects/usb/src/sys/dev/sound/pcm/sound.c#3 edit
> >
> > Differences ...
> >
> > ==== //depot/projects/usb/src/sys/dev/sound/pcm/sound.c#3 (text+ko) ====
> >
> > @@ -78,7 +78,7 @@
> >         m = malloc(sizeof(*m), M_DEVBUF, M_WAITOK | M_ZERO);
> >         if (m == NULL)
> >                 return NULL;
> > -       mtx_init(m, desc, type, MTX_DEF);
> > +       mtx_init(m, desc, type, MTX_DEF|MTX_RECURSE);
> >         return m;
> >  #else
> >         return (void *)0xcafebabe;
>
> Recursed mutexes very often are symptomatic of some some bug...
> it is the case? why the mutex is recursed?
>

Because my system shares the lock with the "pcm channel" of the sound system. 
That means it uses "c->lock" (see below) to protect the isochronous USB 
transfers. The problem is that my USB callback calls "chn_intr()" which also 
locks the same lock.

Maybe this should be addressed by Ariff A. ?

void
chn_intr(struct pcm_channel *c)
{
        CHN_LOCK(c);
        c->interrupts++;
        if (c->direction == PCMDIR_PLAY)
                chn_wrintr(c);
        else
                chn_rdintr(c);
        CHN_UNLOCK(c);
}

--HPS