page fault in shutdown

I got several times page fault when syncing disk but it is
not easy to reproduce.

I have coredump.


All buffers synced.
lock order reversal:
 1st 0xc4083bdc ufs (ufs) _at_ /usr/src/sys/kern/vfs_mount.c:1197
 2nd 0xc40a1488 devfs (devfs) _at_ /usr/src/sys/ufs/ffs/ffs_vfsops.c:1194
KDB: stack backtrace:


Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address	= 0xe6497a80
fault code		= supervisor read, page not present
instruction pointer	= 0x20:0xc05fa097
stack pointer	        = 0x28:0xc399a864
frame pointer	        = 0x28:0xc399a8fc
code segment		= base 0x0, limit 0xfffff, type 0x1b
			= DPL 0, pres 1, def32 1, gran 1
processor eflags	= interrupt enabled, resume, IOPL = 0
current process		= 1 (init)
Physical memory: 1007 MB
Dumping 123 MB: 108 92 76 60 44 28 12

Reading symbols from /boot/KERNEL/sound.ko...Reading symbols from
/boot/KERNEL/sound.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/sound.ko
Reading symbols from /boot/KERNEL/snd_hda.ko...Reading symbols from
/boot/KERNEL/snd_hda.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/snd_hda.ko
Reading symbols from /boot/KERNEL/random.ko...Reading symbols from
/boot/KERNEL/random.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/random.ko
Reading symbols from /boot/KERNEL/acpi.ko...Reading symbols from
/boot/KERNEL/acpi.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/acpi.ko
Reading symbols from /boot/KERNEL/ata.ko...Reading symbols from
/boot/KERNEL/ata.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/ata.ko
Reading symbols from /boot/KERNEL/atapci.ko...Reading symbols from
/boot/KERNEL/atapci.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/atapci.ko
Reading symbols from /boot/KERNEL/ataahci.ko...Reading symbols from
/boot/KERNEL/ataahci.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/ataahci.ko
Reading symbols from /boot/KERNEL/atadisk.ko...Reading symbols from
/boot/KERNEL/atadisk.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/atadisk.ko
Reading symbols from /boot/KERNEL/ataintel.ko...Reading symbols from
/boot/KERNEL/ataintel.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/ataintel.ko
Reading symbols from /boot/KERNEL/cpufreq.ko...Reading symbols from
/boot/KERNEL/cpufreq.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/cpufreq.ko
Reading symbols from /boot/KERNEL/mem.ko...Reading symbols from
/boot/KERNEL/mem.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/mem.ko
Reading symbols from /boot/KERNEL/io.ko...Reading symbols from
/boot/KERNEL/io.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/io.ko
Reading symbols from /boot/KERNEL/sysvmsg.ko...Reading symbols from
/boot/KERNEL/sysvmsg.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/sysvmsg.ko
Reading symbols from /boot/KERNEL/sysvsem.ko...Reading symbols from
/boot/KERNEL/sysvsem.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/sysvsem.ko
Reading symbols from /boot/KERNEL/sysvshm.ko...Reading symbols from
/boot/KERNEL/sysvshm.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/sysvshm.ko
Reading symbols from /boot/KERNEL/nullfs.ko...Reading symbols from
/boot/KERNEL/nullfs.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/nullfs.ko
Reading symbols from /boot/KERNEL/usb.ko...Reading symbols from
/boot/KERNEL/usb.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/usb.ko
Reading symbols from /boot/KERNEL/uhci.ko...Reading symbols from
/boot/KERNEL/uhci.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/uhci.ko
Reading symbols from /boot/KERNEL/ehci.ko...Reading symbols from
/boot/KERNEL/ehci.ko.symbols...done.
done.
Loaded symbols for /boot/KERNEL/ehci.ko
#0  doadump () at pcpu.h:246
246	pcpu.h: No such file or directory.
	in pcpu.h
(kgdb) #0  doadump () at pcpu.h:246
#1  0xc042f539 in db_fncall (dummy1=1, dummy2=0, dummy3=-1064047392,
    dummy4=0xc399a5fc "") at /usr/src/sys/ddb/db_command.c:548
#2  0xc042f931 in db_command (last_cmdp=0xc069c2dc, cmd_table=0x0, dopager=1)
    at /usr/src/sys/ddb/db_command.c:445
#3  0xc042fa8a in db_command_loop () at /usr/src/sys/ddb/db_command.c:498
#4  0xc043199d in db_trap (type=12, code=0) at /usr/src/sys/ddb/db_main.c:229
#5  0xc04e1826 in kdb_trap (type=12, code=0, tf=0xc399a824)
    at /usr/src/sys/kern/subr_kdb.c:534
#6  0xc061586f in trap_fatal (frame=0xc399a824, eva=3863575168)
    at /usr/src/sys/i386/i386/trap.c:924
#7  0xc0615a90 in trap_pfault (frame=0xc399a824, usermode=0, eva=3863575168)
    at /usr/src/sys/i386/i386/trap.c:846
#8  0xc06164f3 in trap (frame=0xc399a824) at /usr/src/sys/i386/i386/trap.c:528
#9  0xc05fb36b in calltrap () at /usr/src/sys/i386/i386/exception.s:165
#10 0xc05fa097 in db_backtrace (td=0xc3d11000, tf=0x0, frame=0xc399a95c,
    pc=3225623030, count=-1) at /usr/src/sys/i386/i386/db_trace.c:413
#11 0xc05fa8c9 in db_trace_self () at /usr/src/sys/i386/i386/db_trace.c:520
#12 0xc04319f6 in db_trace_self_wrapper () at /usr/src/sys/ddb/db_main.c:246
#13 0xc04e1a79 in kdb_backtrace () at /usr/src/sys/kern/subr_kdb.c:300
#14 0xc04f4f75 in _witness_debugger (cond=-431392176,
    msg=0xc062738a "witness_checkorder")
    at /usr/src/sys/kern/subr_witness.c:2799
#15 0xc04f6199 in witness_checkorder (lock=0xc40a1488, flags=9,
    file=0xc06572df "/usr/src/sys/ufs/ffs/ffs_vfsops.c", line=1194,
    interlock=0xc40a14a4) at /usr/src/sys/kern/subr_witness.c:1321
#16 0xc049a187 in __lockmgr_args (lk=0xc40a1488, flags=525312,
    ilk=0xc40a14a4, wmesg=0x0, pri=0, timo=0,
    file=0xc06572df "/usr/src/sys/ufs/ffs/ffs_vfsops.c", line=1194)
    at /usr/src/sys/kern/kern_lock.c:525
#17 0xc052a3e2 in vop_stdlock (ap=0xc399aae0) at lockmgr.h:93
#18 0xc0623b65 in VOP_LOCK1_APV (vop=0xc0681d40, a=0xc399aae0)
    at vnode_if.c:1988
#19 0xc0546c6e in _vn_lock (vp=0xc40a1430, flags=525312,
    file=0xc06572df "/usr/src/sys/ufs/ffs/ffs_vfsops.c", line=1194)
    at vnode_if.h:859
#20 0xc05a8d87 in ffs_flushfiles (mp=0xc41de284, flags=2, td=0xc3d11000)
    at /usr/src/sys/ufs/ffs/ffs_vfsops.c:1194
#21 0xc05a9900 in ffs_unmount (mp=0xc41de284, mntflags=524288)
    at /usr/src/sys/ufs/ffs/ffs_vfsops.c:1084
#22 0xc05349bd in dounmount (mp=0xc41de284, flags=524288, td=0xc3d11000)
    at /usr/src/sys/kern/vfs_mount.c:1287
#23 0xc053ae6e in vfs_unmountall () at /usr/src/sys/kern/vfs_subr.c:3141
#24 0xc04b266d in boot (howto=Variable "howto" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:401
#25 0xc04b2e1b in reboot (td=0xc3d11000, uap=0xc399acf8)
    at /usr/src/sys/kern/kern_shutdown.c:173
#26 0xc0615db3 in syscall (frame=0xc399ad38)
    at /usr/src/sys/i386/i386/trap.c:1073
#27 0xc05fb3d0 in Xint0x80_syscall ()
    at /usr/src/sys/i386/i386/exception.s:261
#28 0x00000033 in ?? ()
Previous frame inner to this frame (corrupt stack?)
(kgdb)


-- 
Paul