From: Nicolas Saenz Julienne <nsaenzju@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>, linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, Minchan Kim <minchan@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Mel Gorman <mgorman@techsingularity.net>,
Juri Lelli <juril@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
"Paul E. McKenney" <paulmck@kernel.org>
Subject: Re: [patch 2/2] mm: lru_cache_disable: replace work queue synchronization with synchronize_rcu
Date: Tue, 22 Feb 2022 16:53:30 +0100 [thread overview]
Message-ID: <b3d35a3e605880034a619e9a3113980107b6d18d.camel@redhat.com> (raw)
In-Reply-To: <20220222144907.056089321@redhat.com>
On Tue, 2022-02-22 at 11:47 -0300, Marcelo Tosatti wrote:
> @@ -918,14 +917,23 @@ atomic_t lru_disable_count = ATOMIC_INIT
> void lru_cache_disable(void)
> {
> atomic_inc(&lru_disable_count);
> + synchronize_rcu();
> #ifdef CONFIG_SMP
> /*
> - * lru_add_drain_all in the force mode will schedule draining on
> - * all online CPUs so any calls of lru_cache_disabled wrapped by
> - * local_lock or preemption disabled would be ordered by that.
> - * The atomic operation doesn't need to have stronger ordering
> - * requirements because that is enforced by the scheduling
> - * guarantees.
> + * synchronize_rcu() waits for preemption disabled
> + * and RCU read side critical sections
> + * For the users of lru_disable_count:
> + *
> + * preempt_disable, local_irq_disable() [bh_lru_lock()]
> + * rcu_read_lock [lru_pvecs CONFIG_PREEMPT_RT]
> + * preempt_disable [lru_pvecs !CONFIG_PREEMPT_RT]
> + *
> + *
> + * so any calls of lru_cache_disabled wrapped by
> + * local_lock+rcu_read_lock or preemption disabled would be
> + * ordered by that. The atomic operation doesn't need to have
> + * stronger ordering requirements because that is enforced
> + * by the scheduling guarantees.
"The atomic operation doesn't need to have stronger ordering requirements
because that is enforced by the scheduling guarantees."
This is no longer needed.
Regards,
--
Nicolás Sáenz
prev parent reply other threads:[~2022-02-22 15:53 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-22 14:47 [patch 0/2] replace work queue synchronization with synchronize_rcu Marcelo Tosatti
2022-02-22 14:47 ` [patch 1/2] mm: protect local lock sections with rcu_read_lock (on RT) Marcelo Tosatti
2022-02-22 15:21 ` Nicolas Saenz Julienne
2022-02-22 15:51 ` Marcelo Tosatti
2022-02-22 16:16 ` Nicolas Saenz Julienne
2022-02-22 14:47 ` [patch 2/2] mm: lru_cache_disable: replace work queue synchronization with synchronize_rcu Marcelo Tosatti
2022-02-22 15:53 ` Nicolas Saenz Julienne [this message]
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