From: Peter Zijlstra <peterz@infradead.org>
To: "Ahmed S. Darwish" <a.darwish@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@kernel.org>,
"Sebastian A. Siewior" <bigeasy@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
linux-mm@kvack.org
Subject: Re: [PATCH v1 02/25] mm/swap: Don't abuse the seqcount latching API
Date: Mon, 25 May 2020 17:45:05 +0200 [thread overview]
Message-ID: <20200525154505.GZ325280@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200525152401.GA375786@debian-buster-darwi.lab.linutronix.de>
On Mon, May 25, 2020 at 05:24:01PM +0200, Ahmed S. Darwish wrote:
> Peter Zijlstra <peterz@infradead.org> wrote:
> > On Tue, May 19, 2020 at 11:45:24PM +0200, Ahmed S. Darwish wrote:
> > > + WRITE_ONCE(lru_drain_gen, lru_drain_gen + 1);
> > > + smp_wmb();
> >
> > You can leave this smp_wmb() out and rely on the smp_mb() implied by
> > queue_work_on()'s test_and_set_bit().
> >
>
> Won't this be too implicit?
>
> Isn't it possible that, over the years, queue_work_on() impementation
> changes and the test_and_set_bit()/smp_mb() gets removed?
>
> If that happens, this commit will get *silently* broken and the local
> CPU pages won't be drained.
Add a comment to queue_work_on() that points here? That way people are
aware.
next prev parent reply other threads:[~2020-05-25 15:45 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-19 21:45 [PATCH v1 00/25] seqlock: Extend seqcount API with associated locks Ahmed S. Darwish
2020-05-19 21:45 ` [PATCH v1 02/25] mm/swap: Don't abuse the seqcount latching API Ahmed S. Darwish
2020-05-20 11:24 ` Hillf Danton
2020-05-20 12:22 ` Konstantin Khlebnikov
2020-05-20 13:05 ` Peter Zijlstra
2020-05-22 14:57 ` Peter Zijlstra
2020-05-22 15:17 ` Sebastian A. Siewior
2020-05-22 16:23 ` Peter Zijlstra
2020-05-25 15:24 ` Ahmed S. Darwish
2020-05-25 15:45 ` Peter Zijlstra [this message]
2020-05-25 16:10 ` John Ogness
[not found] ` <20200827114044.11173-1-a.darwish@linutronix.de>
2020-08-27 11:40 ` [PATCH v1 2/8] mm/swap: Do not abuse the seqcount_t " Ahmed S. Darwish
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