Re: mutexes, locks and so on...

[Andrew Doran <ad%homeworld.netbsd.org@localhost>]

On Wed, Nov 17, 2010 at 03:03:20PM +1100, matthew green wrote:
> 
> > - hppa seems to have a mutex implemented without cas.  is it broken?
> 
> FWIW, the sparc implementation is only broken on SMP.

My recollection is that there were problems with the assembly that we
were using, we didn't get to the bottom of it.  On top of that I think
there is a race condition with the interlock trick that we were going to
use for sparc but I can't remember what it was.  Possibly related to
preemption or interrupts (i.e. mutex_enter inteerupted with the interlock
part held but mutex owner not set). If it comes to me I'll post back.