linux-kernel - Re: [gcv v3 27/35] arm: Replace __get_cpu

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Message-ID: <00000140ea29d3c8-5110dd9f-9dcf-470f-9b7e-4e7ff0874052-000000@email.amazonses.com>
Date:	Wed, 4 Sep 2013 18:09:04 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Will Deacon <will.deacon@....com>
cc:	Tejun Heo <tj@...nel.org>,
	"akpm@...uxfoundation.org" <akpm@...uxfoundation.org>,
	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	Steven Rostedt <srostedt@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [gcv v3 27/35] arm: Replace __get_cpu_var uses

On Wed, 4 Sep 2013, Will Deacon wrote:

> On ARM, yes. I'm worried that there may be an architecture where the change-
> or-fail operation would only fail if the access from the interrupt handler
> *also* used that change-or-fail instruction, which isn't the case with
> this_cpu_inc.
>
> I have no idea if such an architecture exists :)

Atomic operations use atomic_t. this_cpu operations can only use regular
scalars. So the set of variables that are updated by each should be
distinct.



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