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Date: Mon, 25 Sep 2017 14:25:10 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
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        Will Deacon <will.deacon@arm.com>, Andy Lutomirski <luto@kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>
Subject: Re: [RFC PATCH v3 1/2] membarrier: Provide register expedited
 private command
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On Mon, Sep 25, 2017 at 08:10:54PM +0800, Boqun Feng wrote:
> > static void membarrier_register_private_expedited(void)
> > {
> >         struct task_struct *p = current;
> > 
> >         if (READ_ONCE(p->mm->membarrier_private_expedited))
> >                 return;
> >         membarrier_arch_register_private_expedited(p);

Should we not then also do:

	    barrier();

> >         WRITE_ONCE(p->mm->membarrier_private_expedited, 1);
> > }

to avoid the compiler lifting that store?