From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Kautuk Consul <consul.kautuk@gmail.com>,
Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.cz>,
David Rientjes <rientjes@google.com>,
Ionut Alexa <ionut.m.alexa@gmail.com>,
Guillaume Morin <guillaume@morinfr.org>,
linux-kernel@vger.kernel.org, Kirill Tkhai <tkhai@yandex.ru>
Subject: Re: [PATCH 1/1] do_exit(): Solve possibility of BUG() due to race with try_to_wake_up()
Date: Wed, 3 Sep 2014 17:18:48 +0200 [thread overview]
Message-ID: <20140903151848.GA6312@redhat.com> (raw)
In-Reply-To: <20140903144450.GB7083@twins.programming.kicks-ass.net>
On 09/03, Peter Zijlstra wrote:
>
> On Wed, Sep 03, 2014 at 03:36:40PM +0200, Oleg Nesterov wrote:
> >
> > // Ensure that the previous __set_current_state(RUNNING) can't
> > // leak after spin_unlock_wait()
> > smp_mb();
> > spin_unlock_wait();
> > // Another mb to ensure this too can't be reordered with unlock_wait
> > set_current_state(TASK_DEAD);
> >
> > What do you think looks better?
>
> spin_unlock_wait() would be a control dependency right? Therefore that
> store could not creep up anyhow.
Hmm. indeed, thanks! This probably means that task_work_run() can use
rmb() instead of mb().
What I can't understand is do we still need a compiler barrier or not.
Probably "in theory yes" ?
Oleg.
next prev parent reply other threads:[~2014-09-03 15:22 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-25 10:54 [PATCH 1/1] do_exit(): Solve possibility of BUG() due to race with try_to_wake_up() Kautuk Consul
2014-08-25 15:57 ` Oleg Nesterov
2014-08-26 4:45 ` Kautuk Consul
2014-08-26 15:03 ` Oleg Nesterov
2014-09-01 15:39 ` Peter Zijlstra
2014-09-01 17:58 ` Oleg Nesterov
2014-09-01 19:09 ` Peter Zijlstra
2014-09-02 15:52 ` Oleg Nesterov
2014-09-02 16:47 ` Oleg Nesterov
2014-09-02 17:39 ` Peter Zijlstra
2014-09-03 13:36 ` Oleg Nesterov
2014-09-03 14:44 ` Peter Zijlstra
2014-09-03 15:18 ` Oleg Nesterov [this message]
2014-09-04 7:15 ` Peter Zijlstra
2014-09-04 17:03 ` Paul E. McKenney
2014-09-04 5:04 ` Ingo Molnar
2014-09-04 6:32 ` Peter Zijlstra
2014-09-03 16:08 ` task_numa_fault() && TASK_DEAD Oleg Nesterov
2014-09-03 16:33 ` Rik van Riel
2014-09-04 7:11 ` Peter Zijlstra
2014-09-04 10:39 ` Oleg Nesterov
2014-09-04 19:14 ` Hugh Dickins
2014-09-05 11:35 ` Oleg Nesterov
2014-09-03 9:04 ` [PATCH 1/1] do_exit(): Solve possibility of BUG() due to race with try_to_wake_up() Kirill Tkhai
2014-09-03 9:45 ` Peter Zijlstra
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