Re: linux-2.5.18: DRM + cmpxchg issues

george anzinger (george@mvista.com)
Tue, 28 May 2002 17:59:16 -0700


Keith Whitwell wrote:
>
> Adam,
>
> I expect the answer is that we need to dig out the old one.
>
> Previously I don't think the full cmpxchg semantics werere required unless the
> box is smp -- there's no case where atomic operations are required for
> hardware interaction, for example. ...
>
> Probably this changed with preempt, though, so we need one even on UP boxes...
>
I can not think of any reason to need a lock or atomic
operation because of preempt. Even the management of the
preempt on/off flags at most requires memory barriers, even
in SMP boxen. Do you have an example?
-- 
George Anzinger   george@mvista.com
High-res-timers: 
http://sourceforge.net/projects/high-res-timers/
Real time sched:  http://sourceforge.net/projects/rtsched/
Preemption patch:
http://www.kernel.org/pub/linux/kernel/people/rml
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