linux-kernel - Re: [PATCH 2/8] powerpc/pseries: use smp_rmb() in H

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Message-ID: <20200702082840.GC4781@hirez.programming.kicks-ass.net>
Date:   Thu, 2 Jul 2020 10:28:40 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Nicholas Piggin <npiggin@...il.com>
Cc:     Will Deacon <will@...nel.org>, Boqun Feng <boqun.feng@...il.com>,
        Ingo Molnar <mingo@...hat.com>,
        Waiman Long <longman@...hat.com>,
        Anton Blanchard <anton@...abs.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm-ppc@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject: Re: [PATCH 2/8] powerpc/pseries: use smp_rmb() in H_CONFER spin yield

On Thu, Jul 02, 2020 at 05:48:33PM +1000, Nicholas Piggin wrote:
> There is no need for rmb(), this allows faster lwsync here.

Since you determined this; I'm thinking you actually understand the
ordering here. How about recording this understanding in a comment?

Also, should the lock->slock load not use READ_ONCE() ?