Messages in this thread | | | Date | Sat, 30 May 2015 22:49:00 +0200 | From | Oleg Nesterov <> | Subject | Re: [RFC][PATCH 5/5] percpu-rwsem: Optimize readers and reduce global impact |
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On 05/29, Linus Torvalds wrote: > > On Fri, May 29, 2015 at 1:09 PM, Oleg Nesterov <oleg@redhat.com> wrote: > > > > Doesn't it need mb() before "state = readers_slow" to ensure > > "release" semantics? > > Please don't do any mb() at all. Just do smp_store_release() if > release semantics is what you want.
Agreed!
> (And try to make sure to pair it with smp_load_acquire() on the other > side for things to make sense)
Hmm. I think you are right...
__percpu_down_read() lacks another mb() after the "state != BLOCK" check for the same reason, and we can use smp_load_acquire(state) instead.
Oleg.
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