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Message-ID: <a877883d-7ea5-4fc7-7a37-73deeaa9d734@colorfullife.com>
Date: Wed, 13 Jul 2016 20:37:33 +0200
From: Manfred Spraul <manfred@...orfullife.com>
To: Davidlohr Bueso <dave@...olabs.net>,
Michael Ellerman <mpe@...erman.id.au>
Cc: "H. Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...e.hu>, 1vier1@....de,
felixh@...ormatik.uni-bremen.de
Subject: Re: [PATCH 2/2] ipc/sem.c: Remove duplicated memory barriers.
Hi Davidlohr,
On 07/13/2016 06:16 PM, Davidlohr Bueso wrote:
> Manfred, shouldn't this patch be part of patch 1 (as you add the
> unnecessary barriers there? Iow, can we have a single patch for all this?
>
Two reasons:
- patch 1 is safe for backporting, patch 2 not.
- patch 1 is safe on all architectures, for patch 2 I would like to get
some review feedback.
e.g. I just found/read 51d7d5205d33 ("powerpc: Add smp_mb() to
arch_spin_is_locked()"):
For powerpc, a smp_mb() was added into spin_is_locked(), more or less
for ipc/sem.c.
Patch 1 replaces the spin_is_locked() with smp_load_acquire().
Isn't that the proof that smp_mb() is required?
--
Manfred
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