Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH] Document that wake_up(), complete() and co. imply a full memory barrier | Date | Wed, 22 Apr 2009 16:12:06 +0100 |
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Ingo Molnar <mingo@elte.hu> wrote:
> No. They dont generally imply a full memory barrier versus any > arbitrary prior (or following) memory access. > > try_to_wake_up() has an smp_wmb() so it is a write memory barrier > (but not necessarily a read memory barrier). Otherwise there are > spinlocks there but spinlocks are not explicit 'full memory > barriers'.
Blech. That's a good point LOCK...UNLOCK does not imply a full barrier.
So we can't assume that complete(), wake_up() and co. imply any barriers.
All we can assume is that try_to_wake_up() implies a write barrier, but we can't assume that that will be called via __wake_up_common().
David
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