umtx/libthr SMP fixes.

[Bryan Liesner]

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