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From: David Howells <dhowells@redhat.com>
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References: <CA+55aFwMREaiVSZhTt3HB+Qrgj1pA5p9P6q8WD-dSa7=rHYPmQ@mail.gmail.com> <20151102132901.157178466@infradead.org> <20151102134941.005198372@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: dhowells@redhat.com, Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>, Oleg Nesterov <oleg@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>, boqun.feng@gmail.com,
        Jonathan Corbet <corbet@lwn.net>, Michal Hocko <mhocko@kernel.org>,
        Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH 4/4] locking: Introduce smp_cond_acquire()
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Date: Mon, 02 Nov 2015 20:36:49 +0000
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Linus Torvalds <torvalds@linux-foundation.org> wrote:

> > +       smp_read_barrier_depends(); /* ctrl */  \
> > +       smp_rmb(); /* ctrl + rmb := acquire */  \

Doesn't smp_rmb() imply an smp_read_barrier_depends() anyway?  In
memory-barriers.txt, it says:

     Read memory barriers imply data dependency barriers, and so can
     substitute for them.

David