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Date: Thu, 27 Jul 2017 18:59:39 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: Prateek Sood <prsood@codeaurora.org>, mingo@redhat.com,
        sramana@codeaurora.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] rwsem: fix missed wakeup due to reordering of load
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On Thu, Jul 27, 2017 at 11:48:53AM -0400, Waiman Long wrote:
> atomic_long_sub_return_release() is implmented.

I've not had time to really thing about the problem at hand, but this I
can answer:

TSO (x86, s390, sparc): fully serialized
PPC: lwsync; ll/sc	(RCpc)
ARM64: ll/sc-release	(RCsc)
other: smp_mb(); atomic_sub_return_relaxed();