linux-kernel - Re: [PATCH v2 1/2] spinlock: New spinlock_refcount.h for lockless update of refcount

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Date:	Thu, 27 Jun 2013 01:27:19 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andi Kleen <andi@...stfloor.org>
cc:	Waiman Long <waiman.long@...com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jeff Layton <jlayton@...hat.com>,
	Miklos Szeredi <mszeredi@...e.cz>,
	Ingo Molnar <mingo@...hat.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>
Subject: Re: [PATCH v2 1/2] spinlock: New spinlock_refcount.h for lockless
 update of refcount

On Wed, 26 Jun 2013, Andi Kleen wrote:
> On Wed, Jun 26, 2013 at 05:07:02PM -0400, Waiman Long wrote:
> > Looking from the other perspective, we may want the locking code to
> > have the same behavior whether spinlock debugging is enabled or not.
> > Disabling the optimization will cause the code path to differ which
> > may not be what we want. Of course, I can change it if other people
> > also think it is the right way to do it.
> 
> Lock debugging already has quite different timing/lock semantics.

Locks have no timing related sematics and lock debugging does not
change the semantics of locks. Lock debugging adds overhead to the
locking functions, but it does not affect the semantics of locks.

Thanks,

	tglx


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