Date: Fri, 14 May 2010 07:50:42 -0400 From: John Baldwin <jhb@FreeBSD.org> To: Terry Kennedy <TERRY@tmk.com> Cc: freebsd-stable@freebsd.org Subject: Re: Crash dump problem - sleeping thread owns a non-sleepable lock during crash dump write Message-ID: <4BED3912.9080509@FreeBSD.org> In-Reply-To: <01NN32EOXMYC006UN1@tmk.com> References: <01NN32EOXMYC006UN1@tmk.com>
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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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