umtx/libthr SMP fixes.

[Scott Long]

Bryan Liesner wrote:
> On Mon, 2 Jun 2003, Jeff Roberson wrote:
> 
> 
>>If you have had issues with libthr on SMP or umtx panics, the following
>>patch may solve these issues.
>>
>>http://www.chesapeake.net/~jroberson/umtxlocks.diff
>>
>>This patch fixes several race conditions and other issues with umtx.
> 
> 
> Actually, no it doesn't.  I was able to use kern_umtx v 1.3 only if I
> removed atapicam from my kernel config.  These patches (now
> committed?) panic the system whether I use atapicam or not.
> With kern_umtx v1.2 there is no panic at all, with or without
> atapicam.
> 
> Actually, I think it's cam in general that's causing the panic with
> these changes.
> 
> Please see kern/52718

I didn't see a backtrace in the PR.  Is there one that you can share 
with us?

Scott