Re: [PATCH -tip/core/rcu 1/6] Cleanups and fixes for RCU in face of heavy CPU-hotplug stress

Ingo Molnar
2009-08-21T14:18:02Z

* Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:

> I would not trust this architecture for synchronization tests.
> There has been reports of a hardware bug affecting the cmpxchg
> instruction in the field. The load fence normally implied by the
> semantic seems to be missing. AFAIK, AMD never acknowledged the
> problem.

If cmpxchg was broken i'd be having far worse problems and very
widely so.

FYI, this was the same box i prototyped/developed -rt on, which uses
cmpxchg for _everything_.

That's not a proof of course (it's near impossible to prove the lack
of a bug), but it's sure a strong indicator and you'll need to
provide far more proof of misbehavior before i discount a bona fide
regression on this box.

Ingo