RE: [RFC][PATCH] irq_work: Don't ignore possible cmpxchg failure

[Aguirre, Sergio]

> -----Original Message-----
> From: Peter Zijlstra [mailto:a.p.zijlstra@xxxxxxxxx]
> Sent: Tuesday, November 16, 2010 11:09 AM
> To: Aguirre, Sergio
> Cc: LKML; Huang Ying; Martin Schwidefsky; Ingo Molnar; Kyle McMartin
> Subject: RE: [RFC][PATCH] irq_work: Don't ignore possible cmpxchg failure
> 
> On Tue, 2010-11-16 at 10:57 -0600, Aguirre, Sergio wrote:
> 
> > > > @@ -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.
> >
> > But isn't that still leaving the remote possibility of a hidden cmpxchg
> > Failure open?
> 
> No, we don't care if it fails, read the comment. All we want to know is
> that if it still matched, we flipped the bit.

I understand. Will add just a (void) typecast, and resend then.

Regards,
Sergio
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