From: Will Deacon <will.deacon@arm.com>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] barriers: introduce smp_mb__release_acquire and update documentation
Date: Wed, 16 Sep 2015 17:38:14 +0100 [thread overview]
Message-ID: <20150916163813.GP28771@arm.com> (raw)
In-Reply-To: <20150916114918.GA12664@fixme-laptop.cn.ibm.com>
On Wed, Sep 16, 2015 at 12:49:18PM +0100, Boqun Feng wrote:
> Hi Will,
Hello,
> On Tue, Sep 15, 2015 at 05:13:30PM +0100, Will Deacon wrote:
> > +If necessary, ordering can be enforced by use of an
> > +smp_mb__release_acquire() barrier:
> > +
> > + *A = a;
> > + RELEASE M
> > + smp_mb__release_acquire();
>
> Should this barrier be placed after the ACQUIRE? Because we do actually
> want(?) and allow RELEASE and ACQUIRE operations to reorder in this
> case, like your following example, right?
I think it's a lot simpler to keep it where it is, in all honesty. The
relaxation for the RELEASE/ACQUIRE access ordering is mainly there to
allow architectures building those operations out of explicit barriers
to get away without a definition of smp_mb__release_acquire.
Will
next prev parent reply other threads:[~2015-09-16 16:38 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-15 16:13 [PATCH] barriers: introduce smp_mb__release_acquire and update documentation Will Deacon
2015-09-15 17:47 ` Paul E. McKenney
2015-09-16 9:14 ` Peter Zijlstra
2015-09-16 10:29 ` Will Deacon
2015-09-16 10:29 ` Will Deacon
2015-09-16 10:43 ` Peter Zijlstra
2015-09-16 10:43 ` Peter Zijlstra
2015-09-16 11:07 ` Will Deacon
2015-09-16 11:07 ` Will Deacon
2015-09-17 2:50 ` Boqun Feng
2015-09-17 7:57 ` Boqun Feng
2015-09-17 7:57 ` Boqun Feng
2015-09-17 18:00 ` Will Deacon
2015-09-21 13:45 ` Boqun Feng
2015-09-21 13:45 ` Boqun Feng
2015-09-21 14:10 ` Boqun Feng
2015-09-21 14:10 ` Boqun Feng
2015-09-21 22:23 ` Will Deacon
2015-09-21 22:23 ` Will Deacon
2015-09-21 23:42 ` Boqun Feng
2015-09-22 15:22 ` Paul E. McKenney
2015-09-22 15:22 ` Paul E. McKenney
2015-09-22 15:58 ` Will Deacon
2015-09-22 15:58 ` Will Deacon
2015-09-22 16:38 ` Paul E. McKenney
2015-09-16 11:49 ` Boqun Feng
2015-09-16 16:38 ` Will Deacon [this message]
2015-09-17 1:56 ` Boqun Feng
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