linux-kernel - Re: [PATCH] this_cpu: Use this_cpu_xx in trace_functions

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Message-ID: <alpine.DEB.1.10.0910131110110.8088@gentwo.org>
Date:	Tue, 13 Oct 2009 11:14:28 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Tejun Heo <tj@...nel.org>
cc:	Stephen Rothwell <sfr@...b.auug.org.au>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Ingo Molnar <mingo@...e.hu>, linux-next@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] this_cpu: Use this_cpu_xx in trace_functions_graph.c

On Tue, 13 Oct 2009, Tejun Heo wrote:

> > For this_cpu_ptr / __this_cpu_ptr it does not matter. this_cpu_ptr gives
> > you additional checks.
>
> Yes, you're right.  The naming scheme in percpu sucks really hard.
> The subtle differences among [__]get_cpu_var(), [__]this_cpu_ptr() and
> other this_cpu ops.  Arghhhhhh.......

Yeah. __this_cpu_ptr is safe to use in preempt / irq disable sections
though the same way as __this_cpu_add/dec etc.

(__)get_cpu_var can be mostly gotten rid off through __this_cpu
operations.

We could define __get_cpu_var and get_cpu_var using this_cpu

#define get_cpu_var(x) (get_cpu(); this_cpu_read(per_cpu_var(x))

#define __get_cpu_var __this_cpu_read(per_cpu_var(x))


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