panic: Exit: Single threading fouled up

[Dan Nelson]

In the last episode (Apr 26), Gavin Atkinson said:
> I've seen this panic twice now, once on a heavily loaded UP machine
> running gnome at the time, and once on an SMP (hyperthreaded) machine
> which was mostly idle as it was shutting down. Both running with ULE.

I've gotten it 6 times while running the pike testsuite, but not
reliably enough that I can run a WITNESS kernel for a couple hours and
catch it.  SMP system, 4BSD scheduler, libpthread.  Hangs trying to
flush buffers so it has never generated a crashdump.  The couple of
times I was able to break into the debugger before the hang, a ps
showed most of the processes in the system waiting for the "proctree"
mutex.

My trace:

panic: Exit: Single threading fouled up
at line 157 in file ../../../kern/kern_exit.c
cpuid = 1; 
Stack backtrace:
__panic(c075f5cb,9d,c075f611,86,e0589c80) at __panic+0x1a2
exit1(c54d3690,9,c0761f54,971,1) at exit1+0x10e5
sigexit(c54d3690,9,c0761f54,8fd,c4a27aa8) at sigexit+0xff
postsig(9,8,c0764ca5,100,c075f6a6) at postsig+0x32d
ast(e0589d48) at ast+0x2f4
doreti_ast() at doreti_ast+0x17
boot() called on cpu#1
 
-- 
	Dan Nelson
	dnelson at allantgroup.com