7.1 hangs in cache_lookup mutex?

[John Baldwin]

On Thursday 26 February 2009 5:27:07 pm Guy Helmer wrote:
> John Baldwin wrote:
> > On Thursday 26 February 2009 4:22:15 pm Guy Helmer wrote:
> >   
> >> db> show sleepchain 23110
> >> thread 100181 (pid 23110, vmstat) blocked on sx "user map" XLOCK
> >> thread 100208 (pid 23092, kvoop) is on a run queue
> >> db> show sleepchain 23092
> >> thread 100208 (pid 23092, kvoop) is on a run queue
> >>     
> >
> > Ah, so this is normal (well, mostly) in that kvoop is simply on the run 
queue 
> > waiting for a CPU.  Can you find the thread pointer for kvoop and check on 
> > things such as if it is pinned and if so to which CPU (td_pinned will tell 
> > you the first, and td_sched->ts_cpu will tell you the second with ULE).
> >   
> (kgdb) print td->td_pinned
> $2 = 0

Ok, not pinned.

>  From my captured ddb run:
> cpuid        = 3
> curthread    = 0xc5e2f000: pid 23090 "filter"
> curpcb       = 0xe6f90d90
> fpcurthread  = none
> idlethread   = 0xc442daf0: pid 11 "idle: cpu3"
> APIC ID      = 7
> currentldt   = 0x50
> spin locks held:

At http://www.freebsd.org/~jhb/gdb/ you can find my kgdb scripts.  If you 
source gdb6 you can run 'runtds' which will show you what each CPU is doing 
(more or less) in ps-style output.

> I sure wish I could find the root cause of the hangs.  On a hunch, I 
> tried setting "machdep.cpu_idle_hlt=0" on the amd64 machine, and it has 
> run 32 hours without a hang.  It could just be coincidence, though...

Ahhh, that actually could explain it perhaps.  Do your CPUs support C2 or 
higher sleep states for idle?  You can try limiting it to only C1 (or disable 
C1E in your BIOS if it has an option for that) to see if that fixes it.

-- 
John Baldwin