linux-kernel - Re: [RFC][PATCH] irq

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Message-ID: <1277495223.1875.990.camel@laptop>
Date:	Fri, 25 Jun 2010 21:47:03 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Huang Ying <ying.huang@...el.com>, Ingo Molnar <mingo@...e.hu>,
	"H.PeterA" <"nvin hpa"@zytor.com>, linux-kernel@...r.kernel.org,
	tglx <tglx@...utronix.de>, davem <davem@...emloft.net>,
	paulus <paulus@...ba.org>
Subject: Re: [RFC][PATCH] irq_work -v2

On Fri, 2010-06-25 at 21:30 +0200, Andi Kleen wrote:
> > +             entry->next = next_flags(NULL, IRQ_WORK_BUSY);
> > +             entry->func(entry);
> 
> Needs compiler memory barrier here I think.
> 
> > +             /*
> > +              * 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);
> > +     } 

Both the (indirect) function call and the cmpxchg imply a compiler
barrier.
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