linux-kernel - Re: perf events ring buffer memory barrier on powerpc

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Message-ID: <OF58D85F5A.03E37A80-ON42257C12.0070E552-42257C12.00734308@il.ibm.com>
Date:	Mon, 28 Oct 2013 22:58:58 +0200
From:	Victor Kaplansky <VICTORK@...ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Anton Blanchard <anton@...ba.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PPC dev <linuxppc-dev@...abs.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Michael Ellerman <michael@...erman.id.au>,
	Michael Neuling <mikey@...ling.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: perf events ring buffer memory barrier on powerpc

Oleg Nesterov <oleg@...hat.com> wrote on 10/28/2013 10:17:35 PM:

>       mb();   // XXXXXXXX: do we really need it? I think yes.

Oh, it is hard to argue with feelings. Also, it is easy to be on
conservative side and put the barrier here just in case.
But I still insist that the barrier is redundant in your example.

-- Victor

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