linux-kernel - Re: [PATCH] doc: Replace smp_cond_acquire() with smp_cond_load

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Date:   Tue, 10 Jul 2018 16:34:59 +0200
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-doc@...r.kernel.org
Cc:     Alan Stern <stern@...land.harvard.edu>,
        Will Deacon <will.deacon@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Nicholas Piggin <npiggin@...il.com>,
        David Howells <dhowells@...hat.com>,
        Jade Alglave <j.alglave@....ac.uk>,
        Luc Maranget <luc.maranget@...ia.fr>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Akira Yokosawa <akiyks@...il.com>,
        Daniel Lustig <dlustig@...dia.com>,
        Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH] doc: Replace smp_cond_acquire() with
 smp_cond_load_acquire()

On Tue, Jul 10, 2018 at 12:02:23PM +0200, Andrea Parri wrote:
> Amend commit 1f03e8d2919270 ("locking/barriers: Replace smp_cond_acquire()
> with smp_cond_load_acquire()") by updating the documentation accordingly.
> 
> Signed-off-by: Andrea Parri <andrea.parri@...rulasolutions.com>
> Cc: Alan Stern <stern@...land.harvard.edu>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Boqun Feng <boqun.feng@...il.com>
> Cc: Nicholas Piggin <npiggin@...il.com>
> Cc: David Howells <dhowells@...hat.com>
> Cc: Jade Alglave <j.alglave@....ac.uk>
> Cc: Luc Maranget <luc.maranget@...ia.fr>
> Cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
> Cc: Akira Yokosawa <akiyks@...il.com>
> Cc: Daniel Lustig <dlustig@...dia.com>
> Cc: Jonathan Corbet <corbet@....net>
> ---
>  Documentation/memory-barriers.txt | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
> index 0d8d7ef131e9a..987a4e6cc0cd8 100644
> --- a/Documentation/memory-barriers.txt
> +++ b/Documentation/memory-barriers.txt
> @@ -471,8 +471,8 @@ And a couple of implicit varieties:
>       operations after the ACQUIRE operation will appear to happen after the
>       ACQUIRE operation with respect to the other components of the system.
>       ACQUIRE operations include LOCK operations and both smp_load_acquire()
> -     and smp_cond_acquire() operations. The later builds the necessary ACQUIRE
> -     semantics from relying on a control dependency and smp_rmb().
> +     and smp_cond_load_acquire() operations. The later builds the necessary
> +     ACQUIRE semantics from relying on a control dependency and smp_rmb().

Still not completely accurate: smp_rmb() would better be replaced by
smp_acquire__after_ctrl_dep() (arm64 excluded).  Mmh... I think I'll
just remove that "The latter builds the [...]" and resend; thoughts?

  Andrea


>  
>       Memory operations that occur before an ACQUIRE operation may appear to
>       happen after it completes.
> -- 
> 2.7.4
>