Re: panic on 5.2 BETA: blockable sleep lock

On Fri, 2003-11-28 at 01:02, Don Lewis wrote:
> On 27 Nov, Stefan Ehmann wrote:
> > On Wed, 2003-11-26 at 08:33, Don Lewis wrote:
> >> The problem is that selrecord() wants to lock a MTX_DEF mutex, which can
> >> cause a context switch if the mutex is already locked by another thread.
> >> This is contrary to what bktr_poll() wants to accomplish by calling
> >> critical_enter().
> > 
> > Strange enough that does not seem to happen with a kernel built without
> > INVARIANTS and WITNESS. Does this make any sense or is this just by
> > chance?
> 
> You might try the patch below with WITNESS enabled.  I don't have the
> hardware, so I can't test it.  It compiles for me, but for all I know it
> could delete all your files if you run it.

Unfortunately, after running the patched kernel some time I got a
slightly different panic:

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This GDB was configured as "i386-undermydesk-freebsd"...
panic: blockable sleep lock (sleep mutex) sellck _at_
/usr/src/sys/kern/sys_generic.c:1145
panic messages:
---
panic: blockable sleep lock (sleep mutex) sellck _at_
/usr/src/sys/kern/sys_generic.c:1145

syncing disks, buffers remaining... 2248 2248 panic: mi_switch: switch
in a critical section
Uptime: 4m11s
Dumping 383 MB
 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 288 304
320 336 352 368
---
Reading symbols from /boot/kernel/snd_pcm.ko...done.
Loaded symbols for /boot/kernel/snd_pcm.ko
Reading symbols from /boot/kernel/snd_csa.ko...done.
Loaded symbols for /boot/kernel/snd_csa.ko
Reading symbols from /boot/kernel/bktr_mem.ko...done.
Loaded symbols for /boot/kernel/bktr_mem.ko
Reading symbols from
/usr/obj/usr/src/sys/SHOE/modules/usr/src/sys/modules/linprocfs/linprocfs.ko.debug...done.
Loaded symbols for
/usr/obj/usr/src/sys/SHOE/modules/usr/src/sys/modules/linprocfs/linprocfs.ko.debug
Reading symbols from
/usr/obj/usr/src/sys/SHOE/modules/usr/src/sys/modules/linux/linux.ko.debug...done.
Loaded symbols for
/usr/obj/usr/src/sys/SHOE/modules/usr/src/sys/modules/linux/linux.ko.debug
Reading symbols from
/usr/obj/usr/src/sys/SHOE/modules/usr/src/sys/modules/ext2fs/ext2fs.ko.debug...done.
Loaded symbols for
/usr/obj/usr/src/sys/SHOE/modules/usr/src/sys/modules/ext2fs/ext2fs.ko.debug
Reading symbols from
/usr/obj/usr/src/sys/SHOE/modules/usr/src/sys/modules/ntfs/ntfs.ko.debug...done.
Loaded symbols for
/usr/obj/usr/src/sys/SHOE/modules/usr/src/sys/modules/ntfs/ntfs.ko.debug
Reading symbols from /boot/kernel/bktr.ko...done.
Loaded symbols for /boot/kernel/bktr.ko
#0  doadump () at /usr/src/sys/kern/kern_shutdown.c:240
240		dumping++;
(kgdb) bt
#0  doadump () at /usr/src/sys/kern/kern_shutdown.c:240
#1  0xc050f482 in boot (howto=260) at
/usr/src/sys/kern/kern_shutdown.c:372
#2  0xc050f7d8 in panic () at /usr/src/sys/kern/kern_shutdown.c:550
#3  0xc05174e5 in mi_switch () at /usr/src/sys/kern/kern_synch.c:470
#4  0xc050f16e in boot (howto=256) at
/usr/src/sys/kern/kern_shutdown.c:312
#5  0xc050f7d8 in panic () at /usr/src/sys/kern/kern_shutdown.c:550
#6  0xc0535e19 in witness_lock (lock=0xc075c8a0, flags=8, 
    file=0xc06c4d72 "/usr/src/sys/kern/sys_generic.c", line=1145)
    at /usr/src/sys/kern/subr_witness.c:609
#7  0xc0505aaa in _mtx_lock_flags (m=0xc075c8a0, opts=0, 
    file=0xc06f10bc "äLmÀ\t", line=-1009577024)
    at /usr/src/sys/kern/kern_mutex.c:221
#8  0xc053a016 in selrecord (selector=0xc3d313c0, sip=0xc075c8a0)
    at /usr/src/sys/kern/sys_generic.c:1145
#9  0xc4174981 in bktr_close () from /boot/kernel/bktr.ko
#10 0xc04c6650 in spec_poll (ap=0xd8cdbafc)
    at /usr/src/sys/fs/specfs/spec_vnops.c:379
#11 0xc04c5a88 in spec_vnoperate (ap=0x0)
    at /usr/src/sys/fs/specfs/spec_vnops.c:122
#12 0xc057635c in vn_poll (fp=0x0, events=0, active_cred=0xc412b080,
td=0x0)
    at vnode_if.h:537
#13 0xc0539851 in selscan (td=0xc3d313c0, ibits=0xd8cdbb9c,
obits=0xd8cdbb8c, 
    nfd=6) at /usr/src/sys/sys/file.h:272
#14 0xc05393bf in kern_select (td=0xc3d313c0, nd=6, fd_in=0xbfbfeb90, 
    fd_ou=0x0, fd_ex=0x0, tvp=0x0) at
/usr/src/sys/kern/sys_generic.c:816
#15 0xc0539026 in select (td=0x0, uap=0xd8cdbd14)
    at /usr/src/sys/kern/sys_generic.c:720
#16 0xc06827e0 in syscall (frame=
      {tf_fs = 47, tf_es = 47, tf_ds = 47, tf_edi = -1, tf_esi =
134598312, tf_ebp = -1077941208, tf_isp = -657605260, tf_ebx = 0, tf_edx
= 6, tf_ecx = -1077941360, tf_eax = 93, tf_trapno = 12, tf_err = 2,
tf_eip = 673044815, tf_cs = 31, tf_eflags = 658, tf_esp = -1077941444,
tf_ss = 47})
    at /usr/src/sys/i386/i386/trap.c:1010
#17 0xc067444d in Xint0x80_syscall () at {standard input}:136
(kgdb)