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Date: Tue, 14 Jul 2009 16:15:47 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH -tip] ring_buffer: fix warning
Message-ID: <20090714141544.GA5728@nowhere>
References: <4A5C3549.7000905@cn.fujitsu.com>
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On Tue, Jul 14, 2009 at 03:35:37PM +0800, Lai Jiangshan wrote:
> 
> kernel/trace/ring_buffer.c: In function 'rb_tail_page_update':
> kernel/trace/ring_buffer.c:849: warning: value computed is not used
> kernel/trace/ring_buffer.c:850: warning: value computed is not used
> 
> Add a "(void)" to fix this warning.
> 
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index e648ba4..d371279 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -846,8 +846,8 @@ static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
>  		 * not come in and change it. In which case, we
>  		 * do not want to modify it.
>  		 */
> -		local_cmpxchg(&next_page->write, old_write, val);
> -		local_cmpxchg(&next_page->entries, old_entries, eval);
> +		(void)local_cmpxchg(&next_page->write, old_write, val);
> +		(void)local_cmpxchg(&next_page->entries, old_entries, eval);
>  
>  		/*
>  		 * No need to worry about races with clearing out the commit.


Looks good. Indeed the rest of the path remains the same, whether the
interrupts have already won the race or not.

Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>