Re: panic: witness_warn head/amd64 _at_r285741 on 1 of 2 machines

From: Konstantin Belousov <kostikbel_at_gmail.com>
Date: Tue, 21 Jul 2015 22:28:32 +0300
On Tue, Jul 21, 2015 at 07:17:43PM +0000, Mark Johnston wrote:
> On Tue, Jul 21, 2015 at 09:19:27AM -0700, David Wolfskill wrote:
> > On Tue, Jul 21, 2015 at 04:39:07PM +0300, Konstantin Belousov wrote:
> > > On Tue, Jul 21, 2015 at 05:57:34AM -0700, David Wolfskill wrote:
> > > > My laptop had no problems, but the build machine has a panic that
> > > > appears quite reproducible (4 "successes" out of 4 tries); here's a bit
> > > > from the core.txt file:
> > > 
> > > There must be kernel messages before the panic string.  They are crusial
> > > to understand what is going on.
> > > ...
> > 
> > Sorry I wasn't able to capture those before I needed to do Other Things.
> > 
> > The machine had a (PCI-attached) serial console that was working
> > for FreeBSD (thanks mostly to sbruno's help), but Somthing seems
> > to Have Happened, and that's not presently working (even in stable/10,
> > where I first got it working).
> > 
> > I will try to get it working again, but I doubt I will have time to
> > focus on that until about 9 hours from now.
> 
> It's possible to extract log messages leading up to the panic from the
> vmcore. From the kgdb prompt, running
> 
> (kgdb) printf "%s", msgbufp->msg_ptr
> 
> should bring them up.
> 
> And, I just noticed that you posted the core.txt, which contains this
> info near the end:
> http://www.catwhisker.org/~david/FreeBSD/head/core.txt.1

Indeed, thank you.
ithread_loop() at ithread_loop+0xa6/frame 0xfffffe083b9c0a70
fork_exit() at fork_exit+0x84/frame 0xfffffe083b9c0ab0
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe083b9c0ab0
--- trap 0, rip = 0, rsp = 0xfffffe083b9c0b70, rbp = 0 ---
suspending ithread with the following locks held:
shared rw udpinp (udpinp) r = 3 (0xfffff80010c7d7b0) locked _at_ /usr/src/sys/netinet6/in6_pcb.c:1174
panic: witness_warn
cpuid = 3

So it looks like net swi, leaking some udp6 lock.
Received on Tue Jul 21 2015 - 17:28:48 UTC

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