linux-kernel - Re: [PATCH] seqlock: don't smp_rmb in seqlock reader spin loop

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Date:	Thu, 12 May 2011 16:08:32 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Milton Miller <miltonm@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...nel.dk>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Anton Blanchard <anton@...ba.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Eric Dumazet <eric.dumazet@...il.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH] seqlock: don't smp_rmb in seqlock reader spin loop

On Thu, May 12, 2011 at 04:13:54AM -0500, Milton Miller wrote:
> 
> Move the smp_rmb after cpu_relax loop in read_seqlock and add
> ACCESS_ONCE to make sure the test and return are consistent.
> 
> A multi-threaded core in the lab didn't like the update

Which core was that?

-Andi
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