linux-kernel - Re: [patch 3/3] sched: Use local_irq_save_nmi() in cpu

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Message-ID: <20100407112707.GA5143@nowhere>
Date:	Wed, 7 Apr 2010 13:27:12 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	mingo@...e.hu, David Miller <davem@...emloft.net>, acme@...hat.com,
	paulus@...ba.org, Mike Galbraith <efault@....de>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [patch 3/3] sched: Use local_irq_save_nmi() in cpu_clock()

On Tue, Apr 06, 2010 at 03:28:10PM +0200, Peter Zijlstra wrote:
> Since we can call cpu_clock() from NMI context fix up the IRQ
> disabling to conform to the new rules.
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
>  kernel/sched_clock.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6/kernel/sched_clock.c
> ===================================================================
> --- linux-2.6.orig/kernel/sched_clock.c
> +++ linux-2.6/kernel/sched_clock.c
> @@ -241,9 +241,9 @@ unsigned long long cpu_clock(int cpu)
>  	unsigned long long clock;
>  	unsigned long flags;
>  
> -	local_irq_save(flags);
> +	local_irq_save_nmi(flags);
>  	clock = sched_clock_cpu(cpu);
> -	local_irq_restore(flags);
> +	local_irq_restore_nmi(flags);
>  
>  	return clock;
>  }


That seem to add a small overhead in various places.
Do we want to make local_irq_save_nmi == local_irq_save
for archs that have native nmi?

Or cpu_clock_nmi()?

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