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

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Date:	Tue, 20 Sep 2011 18:19:02 -0400
From:	Valdis.Kletnieks@...edu
To:	Christoph Lameter <cl@...two.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>,
	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 Tue, 20 Sep 2011 10:54:10 CDT, Christoph Lameter said:
> IT DOES!!!! The memcg bug is caused by someone using this_cpu_read and
> expecting the cpu not to change. this_cpu_xx ops stand on their own and do
> not guarantee access to the same per cpu area.

As most 6 year olds will tell you, "Well, DUH!".  Maybe if you had called it
"this_cpu_or_maybe_that_one_over_there_read()", people wouldn't use it wrong.

"If people place a nice chocky in their mouth, they don't want their cheeks
pierced. In any case this is an inadequate description of the sweetmeat. I
shall have to ask you to accompany me to the station." -- Monty Python.

"inadequate description" hardly begins to cover the design of this API, which
definitely needs to be taken to the station.

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