Messages in this thread | | | Date | Fri, 29 May 2015 13:41:05 -0700 | Subject | Re: [RFC][PATCH 5/5] percpu-rwsem: Optimize readers and reduce global impact | From | Linus Torvalds <> |
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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.
Basically, strive to avoid "smp_mb()" at all costs. It's insanely expensive compared to pretty much all other serialization alternatives.
(And try to make sure to pair it with smp_load_acquire() on the other side for things to make sense)
Linus
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