linux-kernel - Re: [PATCH v2] introduce atomic_pointer to fix a race condition in cancelable mcs spinlocks

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Message-ID: <538CB78A.8090500@hp.com>
Date:	Mon, 02 Jun 2014 13:42:34 -0400
From:	Waiman Long <waiman.long@...com>
To:	Davidlohr Bueso <davidlohr@...com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Mikulas Patocka <mpatocka@...hat.com>,
	"James E.J. Bottomley" <jejb@...isc-linux.org>,
	Helge Deller <deller@....de>,
	John David Anglin <dave.anglin@...l.net>,
	Parisc List <linux-parisc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	"Vinod, Chegu" <chegu_vinod@...com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Anvin <hpa@...or.com>, Andi Kleen <andi@...stfloor.org>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>,
	Jason Low <jason.low2@...com>
Subject: Re: [PATCH v2] introduce atomic_pointer to fix a race condition in
 cancelable mcs spinlocks

On 06/02/2014 01:12 PM, Davidlohr Bueso wrote:
> On Mon, 2014-06-02 at 10:09 -0700, Linus Torvalds wrote:
>> On Mon, Jun 2, 2014 at 9:25 AM, Peter Zijlstra<peterz@...radead.org>  wrote:
>>> And I can't say I'm a particular fan of these ops either, as alternative
>>> I'm almost inclined to just exclude parisc from using opt spinning.
>> Please do.
> I agree, this is the best way out of this mess. Furthermore, it would
> also be nice to consolidate opt spinning in a common CONFIG option --
> right now mutexes and rwsems create their own dependencies.
>

I would suggest adding a RWSEM_SPIN_ON_OWNER to control opt spinning in 
rwsem. Currently MUTEX_SPIN_ON_OWNER is doing that for mutex, and it is 
disabled when mutex debugging is turned on. So I think it is better to 
allow them to be disabled separately.

-Longman
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