linux-kernel - Re: [PATCH] avoid second smp_processor_id() call in __touch

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Message-ID: <1285173559.2275.1024.camel@laptop>
Date:	Wed, 22 Sep 2010 18:39:19 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Don Zickus <dzickus@...hat.com>,
	Cyrill Gorcunov <gorcunov@...il.com>
Subject: Re: [PATCH] avoid second smp_processor_id() call in
 __touch_watchdog

On Wed, 2010-09-22 at 18:27 +0200, Frederic Weisbecker wrote:
> 
> I'm not sure we want this. This is called by the watchdog internally,
> from the timer or the cpu bound thread, so we probably should better
> keep __get_cpu_var() because it checks that we are not in a preemptable
> section. 

The smp_processor_id() right at the start already does that.

That said, I doubt it really matter one way or the other, compilers have
been known to do CSE for quite a while.
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