linux-kernel - Re: [RFC][PATCH 6/7] freelist: Lock less freelist

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Message-ID: <CAFCw3do_4TrZSQ6kYQ7Y1RYTuD+PfXRyZFp7gSDs2oUXrBZGqQ@mail.gmail.com>
Date:   Thu, 27 Aug 2020 15:57:22 -0400
From:   Cameron <cameron@...dycamel.com>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, mhiramat@...nel.org,
        Eddy_Wu@...ndmicro.com, x86@...nel.org, davem@...emloft.net,
        rostedt@...dmis.org, naveen.n.rao@...ux.ibm.com,
        anil.s.keshavamurthy@...el.com, linux-arch@...r.kernel.org,
        oleg@...hat.com, will@...nel.org, paulmck@...nel.org
Subject: Re: [RFC][PATCH 6/7] freelist: Lock less freelist

On Thu, Aug 27, 2020 at 3:08 PM Boqun Feng <boqun.feng@...il.com> wrote:
> So if try_cmpxchg_acquire() fails, we don't have ACQUIRE semantics on
> read of the new list->head, right? Then probably a
> smp_mb__after_atomic() is needed in that case?

Yes, there needs to be an acquire on the head after a failed cmpxchg;
does the atomic_fetch_add following that not have acquire semantics?

Cameron