linux-kernel - Re: [guv v2 18/31] s390: Replace __get_cpu

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Message-ID: <20130828062737.GA10394@osiris>
Date:	Wed, 28 Aug 2013 08:27:37 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Tejun Heo <tj@...nel.org>, akpm@...uxfoundation.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	linux390@...ibm.com, linux-arch@...r.kernel.org,
	Steven Rostedt <srostedt@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [guv v2 18/31] s390: Replace __get_cpu_var uses

On Mon, Aug 26, 2013 at 08:44:40PM +0000, Christoph Lameter wrote:
> __get_cpu_var() is used for multiple purposes in the kernel source. One of them is
> address calculation via the form &__get_cpu_var(x). This calculates the address for
> the instance of the percpu variable of the current processor based on an offset.


> 4. Retrieve the content of a percpu struct
> 
> 	DEFINE_PER_CPU(struct mystruct, y);
> 	struct mystruct x = __get_cpu_var(y);
> 
>    Converts to
> 
> 	memcpy(this_cpu_ptr(&y), x, sizeof(x));

That's wrong (destination and source should be exchanged).
However your patch looks good.

Acked-by: Heiko Carstens <heiko.carstens@...ibm.com>

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