Re: panic in deadlkres() on r267110

On Fri, Jun 06, 2014 at 11:06:40AM -0400, Glen Barber wrote:
> On Fri, Jun 06, 2014 at 07:23:49AM -0700, Sean Bruno wrote:
> > On Fri, 2014-06-06 at 10:12 -0400, Glen Barber wrote:
> > > Two machines in the cluster panic last night with the same backtrace.
> > > It is unclear yet exactly what was happening on the systems, but both
> > > are port building machines using ports-mgmt/tinderbox.
> > > 
> > > Any ideas or information on how to further debug this would be
> > > appreciated.
> > > 
> > These machines were happily running r266621 previously to this update
> > yesterday.  So, that gives us a bisection point.
> > 
> 
> Some more debug information.  Thank you to Attilio for information on
> what data to get.
> 

Sorry, I did not mask the bits properly.

Script started on Fri Jun  6 15:20:14 2014
command: /bin/sh
# kgdb ./kernel.debug /var/crash/vmcore.0
[...]
#0  doadump (textdump=-946873840) at pcpu.h:219
219             __asm("movq %%gs:%1,%0" : "=r" (td)
(kgdb) p/x allproc_lock.sx_lock
$1 = 0xfffff813ae7f4924
Current language:  auto; currently minimal
(kgdb) p ((struct thread *)0xfffff813ae7f4920)
$4 = (struct thread *) 0xfffff813ae7f4920
(kgdb) p $4->td_tid
$5 = 195038
(kgdb) tid 195038
[Switching to thread 94414 (Thread 195038)]#0  0xffffffff80daf1f8 in cpustop_handler () at /usr/src/sys/amd64/amd64/mp_machdep.c:1432
1432            savectx(&stoppcbs[cpu]);
(kgdb) bt
#0  0xffffffff80daf1f8 in cpustop_handler ()
    at /usr/src/sys/amd64/amd64/mp_machdep.c:1432
#1  0xffffffff80daf1bf in ipi_nmi_handler ()
    at /usr/src/sys/amd64/amd64/mp_machdep.c:1417
#2  0xffffffff80dbfcba in trap (frame=0xfffffe17d5389f30)
    at /usr/src/sys/amd64/amd64/trap.c:189
#3  0xffffffff80da2e03 in nmi_calltrap ()
    at /usr/src/sys/amd64/amd64/exception.S:504
#4  0xffffffff8092fa39 in fork1 (td=0xfffff813ae7f4920, flags=20, pages=Cannot access memory at address 0x4
)
    at /usr/src/sys/kern/kern_fork.c:268
#5  0xffffffff8092f00f in sys_fork (td=0xfffff813ae7f4920, 
    uap=<value optimized out>) at /usr/src/sys/kern/kern_fork.c:106
#6  0xffffffff80dc118b in amd64_syscall (td=0xfffff813ae7f4920, traced=0)
    at subr_syscall.c:133
#7  0xffffffff80da2cab in Xfast_syscall ()
    at /usr/src/sys/amd64/amd64/exception.S:390
#8  0x0000000800d46d1a in ?? ()
Previous frame inner to this frame (corrupt stack?)
(kgdb) 

Glen