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Subject: Re: [PATCH V2 0/6][RFC] futex: FUTEX_LOCK with optional adaptive
 spinning
From: Peter Zijlstra <peterz@infradead.org>
To: Avi Kivity <avi@redhat.com>
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Date: Tue, 06 Apr 2010 16:09:08 +0200
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On Tue, 2010-04-06 at 16:41 +0300, Avi Kivity wrote:
> On 04/06/2010 04:35 PM, Peter Zijlstra wrote:
> > On Tue, 2010-04-06 at 16:28 +0300, Avi Kivity wrote:
> >    
> >> Yes, but that's the best case for spinning.  You could simply use a
> >> userspace spinlock in this case.
> >>      
> > Userspace spinlocks are evil.. they should _never_ be used.
> >    
> 
> But in this case they're fastest.  If we don't provide a non-evil 
> alternative, people will use them.
> 

That's what FUTEX_LOCK is about.