linux-kernel - Re: [pchecks v1 2/4] Use raw cpu ops for calls that would trigger with checks

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Message-ID: <20130924073456.GE28538@gmail.com>
Date:	Tue, 24 Sep 2013 09:34:56 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Christoph Lameter <cl@...ux.com>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	Tejun Heo <tj@...nel.org>, akpm@...uxfoundation.org,
	Steven Rostedt <srostedt@...hat.com>,
	linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>
Subject: Re: [pchecks v1 2/4] Use raw cpu ops for calls that would trigger
 with checks


* Christoph Lameter <cl@...ux.com> wrote:

> Index: linux/kernel/hrtimer.c
> ===================================================================
> --- linux.orig/kernel/hrtimer.c	2013-09-12 13:26:29.216103951 -0500
> +++ linux/kernel/hrtimer.c	2013-09-12 13:26:29.212103994 -0500
> @@ -538,7 +538,7 @@ static inline int hrtimer_is_hres_enable
>   */
>  static inline int hrtimer_hres_active(void)
>  {
> -	return __this_cpu_read(hrtimer_bases.hres_active);
> +	return raw_cpu_read(hrtimer_bases.hres_active);
>  }

If cpu_read() is used, does this check trigger?

If yes, what makes ignoring the check safe? Per change explanation is 
necessary for such annotations.

Thanks,

	Ingo
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