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From: Manfred Spraul <manfred@colorfullife.com>
To: Davidlohr Bueso <dave@stgolabs.net>,
	Michael Ellerman <mpe@ellerman.id.au>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
	1vier1@web.de, felixh@informatik.uni-bremen.de
Subject: Re: [PATCH 2/2] ipc/sem.c: Remove duplicated memory barriers.
Date: Wed, 13 Jul 2016 20:37:33 +0200	[thread overview]
Message-ID: <a877883d-7ea5-4fc7-7a37-73deeaa9d734@colorfullife.com> (raw)
In-Reply-To: <20160713161615.GA2271@linux-80c1.suse>

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

  reply	other threads:[~2016-07-13 18:37 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-13  5:06 [PATCH 0/2] ipc/sem.c: sem_lock fixes Manfred Spraul
2016-07-13  5:06 ` [PATCH 1/2] ipc/sem.c: Fix complex_count vs. simple op race Manfred Spraul
2016-07-13  5:06   ` [PATCH 2/2] ipc/sem.c: Remove duplicated memory barriers Manfred Spraul
2016-07-13 16:16     ` Davidlohr Bueso
2016-07-13 18:37       ` Manfred Spraul [this message]
2016-07-16  1:27   ` [PATCH 1/2] ipc/sem.c: Fix complex_count vs. simple op race Davidlohr Bueso
2016-07-13 22:05 ` [PATCH 0/2] ipc/sem.c: sem_lock fixes Andrew Morton
2016-07-14 16:40   ` Manfred Spraul

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