_mtx_lock_sleep: recursed on non-recursive mutex pcm0

Hi

When trying to play sound from two different sources at the same time I get an
instant panic with the following message
 
panic: _mtx_lock_sleep: recursed on non-recursive mutex pcm0 _at_ /usr/src/sys/dev/sound/pcm/sound.c:381

This is with a <Intel ICH3 (82801CA)> (AC97) on a few hours old current and with
sound and snd_ich compiled staticly into the kernel.
It only occurs when hw.snd.autovchans is set to a number greater than 1.

Backtrace
#0  doadump () at pcpu.h:165
#1  0xc059674a in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:397
#2  0xc0596ab8 in panic (
    fmt=0xc07d07d0 "_mtx_lock_sleep: recursed on non-recursive mutex %s _at_ %s:%d\n")
    at /usr/src/sys/kern/kern_shutdown.c:553
#3  0xc058cc08 in _mtx_lock_sleep (m=0xc1be9bc0, td=0xc20d8190, opts=0, file=0x0, 
    line=0) at /usr/src/sys/kern/kern_mutex.c:447
#4  0xc058c8eb in _mtx_lock_flags (m=0x0, opts=0, 
    file=0xc07c5c1a "/usr/src/sys/dev/sound/pcm/sound.c", line=381)
    at /usr/src/sys/kern/kern_mutex.c:273
#5  0xc0506dfc in pcm_chn_create (d=0xc1979a00, parent=0x0, cls=0x0, dir=2, 
    devinfo=0x0) at /usr/src/sys/dev/sound/pcm/sound.c:381
#6  0xc0508a52 in vchan_create (parent=0xc1bf0180)
    at /usr/src/sys/dev/sound/pcm/vchan.c:265
#7  0xc05067a4 in pcm_chnalloc (d=0xc1979a00, direction=1, pid=628, chnum=-1)
    at /usr/src/sys/dev/sound/pcm/sound.c:193
#8  0xc0500a8d in dsp_open (i_dev=0xc1a99c00, flags=2, mode=8192, td=0xc20d8190)
    at /usr/src/sys/dev/sound/pcm/dsp.c:275
#9  0xc053e38b in devfs_open (ap=0xeebb8a54)
    at /usr/src/sys/fs/devfs/devfs_vnops.c:881
#10 0xc0792fbc in VOP_OPEN_APV (vop=0x0, a=0xeebb8a54) at vnode_if.c:373
#11 0xc06089c2 in vn_open_cred (ndp=0xeebb8bc4, flagp=0xeebb8cc4, cmode=0, 
    cred=0xc20a5900, fdidx=6) at vnode_if.h:198
#12 0xc0608543 in vn_open (ndp=0x0, flagp=0x0, cmode=0, fdidx=0)
    at /usr/src/sys/kern/vfs_vnops.c:91
#13 0xc0600668 in kern_open (td=0xc20d8190, path=0x0, pathseg=UIO_USERSPACE, 
    flags=2, mode=0) at /usr/src/sys/kern/vfs_syscalls.c:986
#14 0xc0600556 in open (td=0x0, uap=0xeebb8d04)
    at /usr/src/sys/kern/vfs_syscalls.c:952

The content of frame 5 yields the following
(kgdb) f 5
#5  0xc0506dfc in pcm_chn_create (d=0xc1979a00, parent=0x0, cls=0x0, dir=2, 
    devinfo=0x0) at /usr/src/sys/dev/sound/pcm/sound.c:381
381             snd_mtxlock(d->lock);

d->lock is initialized as a non-recursive mutex in snd_mtxcreate (sound.c:78) 
called from pcm_register (sound.c:655).
While the following patch fixes the panic and let me play sound from different
sources at the same time without any problems, I'm really not sure this is
the correct solution since the mutex was initialized as a non-recursive mutex but
recursion happens anyway. Perhaps somebody with more experience in the sound system
could look at this.

--- sound.c.orig        Wed Jun  8 16:07:32 2005
+++ sound.c     Wed Jun  8 15:32:19 2005
_at__at_ -75,7 +75,7 _at__at_
        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;

 
   Fredrik Lindberg