linux-kernel - Re: [RFC][PATCH] irq_work: Don't ignore possible cmpxchg failure

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Message-ID: <1289925901.2109.629.camel@laptop>
Date:	Tue, 16 Nov 2010 17:45:01 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Sergio Aguirre <saaguirre@...com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Huang Ying <ying.huang@...el.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>, Kyle McMartin <kyle@...artin.ca>
Subject: Re: [RFC][PATCH] irq_work: Don't ignore possible cmpxchg failure

On Tue, 2010-11-16 at 10:32 -0600, Sergio Aguirre wrote:
> Although is very unlikely, it's better to make sure we're not
> letting this happen.
> 
> This solves this compilation warning:
> 
> kernel/irq_work.c: In function 'irq_work_run':
> kernel/irq_work.c:148: warning: value computed is not used
> 

> @@ -145,7 +145,10 @@ void irq_work_run(void)
>  		 * Clear the BUSY bit and return to the free state if
>  		 * no-one else claimed it meanwhile.
>  		 */
> -		cmpxchg(&entry->next, next_flags(NULL, IRQ_WORK_BUSY), NULL);
> +		xchgres = cmpxchg(&entry->next,
> +				  next_flags(NULL, IRQ_WORK_BUSY),
> +				  NULL);
> +		BUG_ON(unlikely(xchgres != next_flags(NULL, IRQ_WORK_BUSY)));

simply adding (void) in front would be much easier.
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