Terry Kennedy wrote:
> I'm reposting this over here at the suggestion of the Forums moderator.
> The original post is at http://forums.freebsd.org/showthread.php?t=14163
>
> Got an interesting crash just now (well, as interesting as a crash on a
> soon-to-be production system can be).
>
> This is 8-STABLE/amd64, last cvsup'd early in the morning of May 9th.
>
> The system didn't complete the crash dump, so it needed a manual reset to get
> it going again.
>
> The crash was a "page fault while in kernel mode" with the current process
> being the interrupt service routine for the bce0 GigE. Things progressed
> reasonably until partway through the dump, when the system locked up with a
> "Sleeping thread (tid 100028, pid 12) owns a non-sleepable lock". That's the
> same PID as reported in the main crash.
Hmm. You could try changing the code to not do a nested panic in that
case. You would update subr_turnstile.c to just return if panicstr is
not NULL rather than calling panic. However, there is still a good
chance you will end up deadlocking in that case. I have another patch I
can send you next week that prevents blocking on mutexes duing a panic
which may also help.
> 3) Is there any way to rig the system to obtain more info if this happens
> again? Right now I'm using an embedded remote console server, but I could
> switch the system to a serial port if enabling the kernel debugger might help.
> But I think that the sleeping thread bit would happen even at the debugger
> prompt, wouldn't it?
Include DDB and enable the 'trace_on_panic' sysctl knob perhaps.
> I just booted the new kernel and tried this again, and got another crash. The
> message is identical to the first, except that the instruction pointer changed
> by 0x10 (presumably due to code differences between the old and new kernels)
> and it got 6MB further writing the crash dump.
>
> Since it seems I can reproduce this at will, I'll be glad to either perform
> additional information-gathering or give a developer access to the box for
> testing purposes.
>
> Is it possible to correlate the source line in the kernel with the instruction
> pointer in the panic?
If you are booted into the same kernel with the same modules loaded, you
can probably run 'kgdb' as root do 'l *<instruction pointer>'.
--
John Baldwin
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