Date: Mon, 1 Mar 2004 15:07:20 -0800 (PST) From: Don Lewis <truckman@FreeBSD.org> To: jhb@FreeBSD.org Cc: current@FreeBSD.org Subject: Re: panic: sound mutex assertion failure Message-ID: <200403012307.i21N7K7E096269@gw.catspoiler.org> In-Reply-To: <200403011307.57831.jhb@FreeBSD.org>
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On 1 Mar, John Baldwin wrote: > panic: _mtx_lock_sleep: recursed on non-recursive mutex pcm0 > @ ../../../dev/sound/pcm/sound.c:395 > > at line 436 in file ../../../kern/kern_mutex.c > > syncing disks, buffers remaining... 2169 panic: bremfree: removing a buffer > not on a queue > at line 647 in file ../../../kern/vfs_bio.cUptime: 3m31s > Dumping 1023 MB > 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 288 304 320 336 > 352 368 384 400 416 432 448 464 480 496 512 528 544 560 576 592 608 624 640 > 656 672 688 704 720 736 752 768 784 800 816 832 848 864 880 896 912 928 944 > 960 976 992 1008 > --- > (kgdb) where > #0 doadump () at ../../../kern/kern_shutdown.c:240 > #1 0xc0581e1c in boot (howto=260) at ../../../kern/kern_shutdown.c:374 > #2 0xc0582186 in poweroff_wait (junk=0xc074a317, howto=647) > at ../../../kern/kern_shutdown.c:552 > #3 0xc05c450c in bremfreel (bp=0xe7a83748) at ../../../kern/vfs_bio.c:647 > #4 0xc05c43cc in bremfree (bp=0x0) at ../../../kern/vfs_bio.c:629 > #5 0xc05c7f45 in getblk (vp=0x0, blkno=12000, size=4096, slpflag=0, > slptimeo=0, flags=0) at ../../../kern/vfs_bio.c:2466 > #6 0xc0687ff4 in ffs_sbupdate (mp=0xc6541500, waitfor=2) > at ../../../ufs/ffs/ffs_vfsops.c:1499 > #7 0xc0687990 in ffs_sync (mp=0xc654dc00, waitfor=2, cred=0xc2272e80, > td=0xc07c0800) at ../../../ufs/ffs/ffs_vfsops.c:1224 > #8 0xc05d9a09 in sync (td=0xc07c0800, uap=0x0) > at ../../../kern/vfs_syscalls.c:141 > #9 0xc0581a4b in boot (howto=256) at ../../../kern/kern_shutdown.c:306 > #10 0xc0582186 in poweroff_wait (junk=0xc0744aa9, howto=436) > at ../../../kern/kern_shutdown.c:552 > #11 0xc0578a3e in _mtx_lock_sleep (m=0xe7a83904, opts=0, file=0x0, line=0) > at ../../../kern/kern_mutex.c:479 > #12 0xc0578658 in _mtx_lock_flags (m=0x0, opts=0, > file=0xc0739490 "../../../dev/sound/pcm/sound.c", line=395) > at ../../../kern/kern_mutex.c:251 > #13 0xc051983d in pcm_chn_create (d=0xc6319800, parent=0x0, cls=0x0, > dir=-1066167152, devinfo=0x0) at ../../../dev/sound/pcm/sound.c:395 > #14 0xc051b26c in vchan_create (parent=0xc6300a80) > at ../../../dev/sound/pcm/vchan.c:265 > #15 0xc0519259 in pcm_chnalloc (d=0xc6319800, direction=1, pid=720, chnum=-1) > at ../../../dev/sound/pcm/sound.c:209 > #16 0xc051482c in dsp_open (i_dev=0xc07c2eb0, flags=7, mode=8192, > td=0xc68653f0) at ../../../dev/sound/pcm/dsp.c:274 > #17 0xc054871d in spec_open (ap=0xe7a83a64) > at ../../../fs/specfs/spec_vnops.c:207 > #18 0xc0548470 in spec_vnoperate (ap=0x0) > at ../../../fs/specfs/spec_vnops.c:122 > #19 0xc05e1a4e in vn_open_cred (ndp=0xe7a83bdc, flagp=0xe7a83cdc, cmode=0, > cred=0xc68cd580, fdidx=0) at vnode_if.h:228 > #20 0xc05e1623 in vn_open (ndp=0x0, flagp=0x0, cmode=0, fdidx=0) > at ../../../kern/vfs_vnops.c:93 > #21 0xc05dae8b in kern_open (td=0xc68653f0, path=0x0, pathseg=UIO_USERSPACE, > flags=7, mode=0) at ../../../kern/vfs_syscalls.c:963 > #22 0xc05dadb7 in open (td=0x0, uap=0x0) at ../../../kern/vfs_syscalls.c:933 It's interesting that nobody has run into this before. I suspect that the reason is that the mutexes in the sound code used the MTX_RECURSE flag, which I recently removed, and since that time vchans have gotten very little use (and probably not much use before, either). This is an area that I was planning to work on fairly soon, but in the meantime, I think you can avoid this bug by pre-creating vchans by setting hw.snd.pcm0.vchans. Thanks for the bug report. It will be helpful when I crank out my next locking patch. BTW, I'm now thinking it would be more better to use some flags and msleep()/wakeup() rather than adding an sx lock for the next step.
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