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Date: Thu, 11 Aug 2011 10:12:00 +0300
From: Andriy Gapon <avg@FreeBSD.org>
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To: Steven Hartland <killing@multiplay.co.uk>
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Cc: freebsd-stable@FreeBSD.org
Subject: Re: debugging frequent kernel panics on 8.2-RELEASE
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on 10/08/2011 18:35 Steven Hartland said the following:
> Fatal double fault
> rip = 0xffffffff8052f6f1
> rsp = 0xffffff86ce600fb0
> rbp = 0xffffff86ce601210
> cpuid = 0; apic id = 00
> panic: double fault
> cpuid = 0
> KDB: stack backtrace:
> #0 0xffffffff803af91e at kdb_backtrace+0x5e
> #1 0xffffffff8037d817 at panic+0x187
> #2 0xffffffff80574316 at dblfault_handler+0x96
> #3 0xffffffff8055d06d at Xdblfault+0xad
[snip]
> #0  sched_switch (td=0xffffffff80830bc0, newtd=0xffffff000a73f8c0, flags=Variable
> "flags" is not available.)
>    at /usr/src/sys/kern/sched_ule.c:1858
> 1858                    cpuid = PCPU_GET(cpuid);
> (kgdb)
> #0  sched_switch (td=0xffffffff80830bc0, newtd=0xffffff000a73f8c0, flags=Variable
> "flags" is not available.)
>    at /usr/src/sys/kern/sched_ule.c:1858
> #1  0xffffffff80385c86 in mi_switch (flags=260, newtd=0x0)
>    at /usr/src/sys/kern/kern_synch.c:449
> #2  0xffffffff803b92d2 in sleepq_timedwait (wchan=0xffffffff80830760, pri=68)
>    at /usr/src/sys/kern/subr_sleepqueue.c:644
> #3  0xffffffff803861e1 in _sleep (ident=0xffffffff80830760, lock=0x0,
>    priority=Variable "priority" is not available.
> ) at /usr/src/sys/kern/kern_synch.c:230
> #4  0xffffffff80532c29 in scheduler (dummy=Variable "dummy" is not available.
> ) at /usr/src/sys/vm/vm_glue.c:807
> #5  0xffffffff80335d67 in mi_startup () at /usr/src/sys/kern/init_main.c:254
> #6  0xffffffff8016efac in btext () at /usr/src/sys/amd64/amd64/locore.S:81
> #7  0xffffffff808556e0 in sleepq_chains ()
> #8  0xffffffff8083b1e0 in cpu_top ()
> #9  0x0000000000000000 in ?? ()
> #10 0xffffffff80830bc0 in proc0 ()
> #11 0xffffffff80ba4b90 in ?? ()
> #12 0xffffffff80ba4b38 in ?? ()
> #13 0xffffff000a73f8c0 in ?? ()
> #14 0xffffffff803a2cc9 in sched_switch (td=0x0, newtd=0x0, flags=Variable "flags"
> is not available.
> )
>    at /usr/src/sys/kern/sched_ule.c:1852
> Previous frame inner to this frame (corrupt stack?)
> (kgdb)

Looks like this is just the first thread in the kernel.
Perhaps 'thread apply all bt' could help to find the culprit.

-- 
Andriy Gapon