linux-kernel - Re: [RFC][PATCH 2/5] mm: Switch mod_state() to __this_cpu

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Date:	Mon, 19 Sep 2011 17:02:13 -0500 (CDT)
From:	Christoph Lameter <cl@...two.org>
To:	Steven Rostedt <rostedt@...dmis.org>
cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Christoph Lameter <cl@...ux.com>
Subject: Re: [RFC][PATCH 2/5] mm: Switch mod_state() to __this_cpu_read()

On Mon, 19 Sep 2011, Steven Rostedt wrote:

> From: Steven Rostedt <srostedt@...hat.com>
>
> The code in mod_state() is already made to handle the raciness of
> this_cpu_read(). Have the code use __this_cpu_read() instead so
> the debug code does not trigger warnings about it.

Why would there be a warning triggered? this_cpu_read should take care of
disabling preemption for the read if needed. In fact the fallback case
does do exactly that.

I think it would make more sence if __this_cpu_read() could be made to
trigger a warning if used in context where preemption could be off.

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