Re: allow preemption in check_task_state
From: Peter Zijlstra <peterz@infradead.org>
Date: 2014-02-10 17:38:51
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On Mon, Feb 10, 2014 at 06:17:12PM +0100, Nicholas Mc Guire wrote:
maybe I'm missing/missunderstanding something here but pi_unlock -> arch_spin_unlock is a full mb()
Nope, arch_spin_unlock() on x86 is a single add[wb] without LOCK prefix. The lock and unlock primitives are in general specified to have ACQUIRE resp. RELEASE semantics. See Documentation/memory-barriers.txt for far too much head-hurting details.