Date: Fri, 31 Jul 2015 10:39:20 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <Waiman.Long@hp.com>
Cc: Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, Scott J Norton <scott.norton@hp.com>,
        Douglas Hatch <doug.hatch@hp.com>, Davidlohr Bueso <dave@stgolabs.net>
Subject: Re: [PATCH v3 1/7] locking/pvqspinlock: Unconditional PV kick with
 _Q_SLOW_VAL
Message-ID: <20150731083920.GD19282@twins.programming.kicks-ass.net>
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On Wed, Jul 22, 2015 at 04:12:36PM -0400, Waiman Long wrote:
> The smp_store_release() is not a full barrier. In order to avoid missed
> wakeup, we may need to add memory barrier around locked and cpu state
> variables adding to complexity. As the chance of spurious wakeup is very
> low, it is easier and safer to just do an unconditional kick at unlock
> time.

This needs to better spell out the race; my still sleeping brain doesn't
want to co-operate and its generally better to spell out these things
anyway.
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