linux-kernel - Re: [PATCH v2 optional 3/3] mutex: back out architecture specific check for negative mutex count

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Date:	Tue, 16 Apr 2013 11:05:05 +0100
From:	Will Deacon <will.deacon@....com>
To:	Waiman Long <Waiman.Long@...com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	David Howells <dhowells@...hat.com>,
	Dave Jones <davej@...hat.com>,
	Clark Williams <williams@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	"Norton, Scott J" <scott.norton@...com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH v2 optional 3/3] mutex: back out architecture specific
 check for negative mutex count

On Mon, Apr 15, 2013 at 03:37:59PM +0100, Waiman Long wrote:
> If it is confirmed that all the supported architectures can allow a
> negative mutex count without incorrect behavior, we can then back
> out the architecture specific change and allow the mutex count to
> go to any negative number. That should further reduce contention for
> non-x86 architecture.
> 
> If this is not the case, this patch should be dropped.

A good starting point might be to look at the asm-generic mutex
implementations, which clears up the majority of architectures. A cursory
glance at mutex-dec.h suggests that it's OK to me...

Will
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