PLEASE TEST: IPI deadlock avoidance patch

[John Baldwin]

On Sunday 22 August 2004 03:05 pm, Doug White wrote:
> Hey folks,
>
> If you have a reasonably fast i386 or amd64 multiprocessor and/or
> hyperthreading machine and are experiencing reproducible hangs during -j
> buildwords and other highly parallel operations, please try this patch:
>
> http://people.freebsd.org/~dwhite/smp_rv_mtx.patch
>
> This patch avoids a deadlock between the smp_rendezvous() mechanism and
> TLB shootdowns via pmap by forcing them to share a mutex.  The patch has
> been tested on several multiproc Xeon systems and a dual Opteron I have
> here and is stable, but a couple of more eyeballs and varied loads
> wouldn't hurt since this will be going into RELENG_5.
>
> If there's anything glaringly wrong from a style point of view, let me
> know too.
>
> I plan on committing this late Monday or Tuesday, barring any serious
> problems.
>
> Thanks to alc for the nudge on the solution and rwatson for staying up
> late and testing it on his hardware.

Looks good to me.  I also think this might help the KSE + SMP hangs.  Only 
suggestion I might have is to rename smp_rv_mtx to smp_ipi_mtx and "SMP IPI 
lock" or some such.

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org