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Date: Thu, 29 Dec 2005 11:46:25 -0500 (EST)
From: Nicolas Pitre <nico@cam.org>
Subject: Re: [patch 1/3] mutex subsystem: trylock
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To: Ingo Molnar <mingo@elte.hu>
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On Thu, 29 Dec 2005, Ingo Molnar wrote:

> > I'd solve it like this instead (on top of your latest patches):
> 
> thanks, applied.
> 
> > +		"1: ldrex	%0, [%3]	\n"
> > +		"subs		%1, %0, #1	\n"
> > +		"strexeq	%2, %1, [%3]	\n"
> > +		"movlt		%0, #0		\n"
> > +		"cmpeq		%2, #0		\n"
> > +		"bgt		1b		\n"
> 
> so we are back to what is in essence a cmpxchg implementation?

A limited cmpxchg.  Using the generic cmpxchg for this would need either 
9 or 10 instructions instead of 6.


Nicolas