dtrace/cyclic deadlock

[Andriy Gapon]

on 23/11/2010 08:33 Andriy Gapon said the following:
> I think that this is quite similar to what we do for per-CPU caches in UMA and
> so the same approach should work here.
> That is, as in (Open)Solaris, the data should be accessed only from the owning
> CPU and spinlock_enter()/spinlock_exit() should be used to prevent races between
> non-interrupt code and nested interrupt code.

Here's a patch that makes our version of cyclic.c a little bit closer to the
upstream version whilst implementing the above idea:
http://people.freebsd.org/~avg/cyclic-deadlock.diff

All accesses to per-CPU cyclics data are performed strictly from the corresponding
CPUs in an interrupt or interrupt-like context.  "Upcalls" occur in event timer's
interrupt filter and all down calls are performed via smp_rendezvous_cpus().

I will appreciate reviews and testing.
Thanks!
-- 
Andriy Gapon