panic: spin lock held too long (RELENG_8 from today)

[Chip Camden]

Quoth Hiroki Sato on Friday, 19 August 2011:
> Chip Camden <sterling at camdensoftware.com> wrote
>   in <20110818025550.GA1971 at libertas.local.camdensoftware.com>:
> 
> st> Quoth Attilio Rao on Thursday, 18 August 2011:
> st> > In callout_cpu_switch() if a low priority thread is migrating the
> st> > callout and gets preempted after the outcoming cpu queue lock is left
> st> > (and scheduled much later) we get this problem.
> st> >
> st> > In order to fix this bug it could be enough to use a critical section,
> st> > but I think this should be really interrupt safe, thus I'd wrap them
> st> > up with spinlock_enter()/spinlock_exit(). Fortunately
> st> > callout_cpu_switch() should be called rarely and also we already do
> st> > expensive locking operations in callout, thus we should not have
> st> > problem performance-wise.
> st> >
> st> > Can the guys I also CC'ed here try the following patch, with all the
> st> > initial kernel options that were leading you to the deadlock? (thus
> st> > revert any debugging patch/option you added for the moment):
> st> > http://www.freebsd.org/~attilio/callout-fixup.diff
> st> >
> st> > Please note that this patch is for STABLE_8, if you can confirm the
> st> > good result I'll commit to -CURRENT and then backmarge as soon as
> st> > possible.
> st> >
> st> > Thanks,
> st> > Attilio
> st> >
> st>
> st> Thanks, Attilio.  I've applied the patch and removed the extra debug
> st> options I had added (though keeping debug symbols).  I'll let you know if
> st> I experience any more panics.
> 
>  No panic for 20 hours at this moment, FYI.  For my NFS server, I
>  think another 24 hours would be sufficient to confirm the stability.
>  I will see how it works...
> 
> -- Hiroki

Likewise:

$ uptime
 5:37PM  up 21:45, 5 users, load averages: 0.68, 0.45, 0.63

So far, so good (knocks on head).

-- 
.O. | Sterling (Chip) Camden      | http://camdensoftware.com
..O | sterling at camdensoftware.com | http://chipsquips.com
OOO | 2048R/D6DBAF91              | http://chipstips.com
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