linux-kernel - Re: [thisops uV2 05/10] x86: Use this_cpu_inc

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Message-ID: <20101127150049.GF15365@Krystal>
Date:	Sat, 27 Nov 2010 10:00:49 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	akpm@...ux-foundation.org, Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Tejun Heo <tj@...nel.org>
Subject: Re: [thisops uV2 05/10] x86: Use this_cpu_inc_return for nmi
	counter

* Christoph Lameter (cl@...ux.com) wrote:
> this_cpu_inc_return() saves us a memory access there.
> 

Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

> Reviewed-by: Tejun Heo <tj@...nel.org>
> Signed-off-by: Christoph Lameter <cl@...ux.com>
> 
> ---
>  arch/x86/kernel/apic/nmi.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> Index: linux-2.6/arch/x86/kernel/apic/nmi.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/apic/nmi.c	2010-11-23 16:35:19.000000000 -0600
> +++ linux-2.6/arch/x86/kernel/apic/nmi.c	2010-11-23 16:38:29.000000000 -0600
> @@ -432,8 +432,7 @@ nmi_watchdog_tick(struct pt_regs *regs,
>  		 * Ayiee, looks like this CPU is stuck ...
>  		 * wait a few IRQs (5 seconds) before doing the oops ...
>  		 */
> -		__this_cpu_inc(alert_counter);
> -		if (__this_cpu_read(alert_counter) == 5 * nmi_hz)
> +		if (__this_cpu_inc_return(alert_counter) == 5 * nmi_hz)
>  			/*
>  			 * die_nmi will return ONLY if NOTIFY_STOP happens..
>  			 */
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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