linux-kernel - Re: [Use cpuops V1 09/11] Connector: Use this

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Message-ID: <4CFE4DDF.7010104@kernel.org>
Date:	Tue, 07 Dec 2010 16:08:15 +0100
From:	Tejun Heo <tj@...nel.org>
To:	Christoph Lameter <cl@...ux.com>
CC:	akpm@...ux-foundation.org, Scott James Remnant <scott@...ntu.com>,
	Mike Frysinger <vapier@...too.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [Use cpuops V1 09/11] Connector: Use this_cpu operations

On 12/06/2010 06:16 PM, Christoph Lameter wrote:
> get_seq can benefit from this_cpu_operations. Address calculation is avoided
> and the increment is done using an xadd.
> 
> Cc: Scott James Remnant <scott@...ntu.com>
> Cc: Mike Frysinger <vapier@...too.org>
> Signed-off-by: Christoph Lameter <cl@...ux.com>
> 
> ---
>  drivers/connector/cn_proc.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6/drivers/connector/cn_proc.c
> ===================================================================
> --- linux-2.6.orig/drivers/connector/cn_proc.c	2010-11-30 09:38:33.000000000 -0600
> +++ linux-2.6/drivers/connector/cn_proc.c	2010-11-30 09:39:38.000000000 -0600
> @@ -43,9 +43,10 @@ static DEFINE_PER_CPU(__u32, proc_event_
>  
>  static inline void get_seq(__u32 *ts, int *cpu)
>  {
> -	*ts = get_cpu_var(proc_event_counts)++;
> +	preempt_disable();
> +	*ts = __this_cpu_inc(proc_event_counts);

Eh?  __this_cpu_inc() evaluates to the incremented value?

-- 
tejun
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