linux-kernel - Re: [PATCH v4 1/3] qrwlock: A queue read/write lock implementation

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Message-ID: <alpine.DEB.2.02.1310241207500.4983@ionos.tec.linutronix.de>
Date:	Thu, 24 Oct 2013 12:14:58 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Waiman Long <waiman.long@...com>
cc:	walken@...gle.com, Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
	linux-arch@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Rik van Riel <riel@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	George Spelvin <linux@...izon.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>
Subject: Re: [PATCH v4 1/3] qrwlock: A queue read/write lock implementation

On Wed, 23 Oct 2013, Waiman Long wrote:
> On 10/23/2013 08:00 AM, walken@...gle.com wrote:
> > > +	/*
> > > +	 * Wait until the next one in queue set up the next field
> > > +	 */
> > > +	while (likely(!(next = ACCESS_ONCE(node->next))))
> > > +		cpu_relax();
> > > +	/*
> > > +	 * The next one in queue is now at the head
> > > +	 */
> > > +notify_next:
> > > +	barrier();
> > > +	ACCESS_ONCE(next->wait) = false;
> > > +	smp_wmb();
> > > +}
> > I believe this could be unified with mspin_lock() / mspin_unlock() in
> > kernel/mutex.c ? (there is already talk of extending these functions
> > to be used by rwsem for adaptive spinning as well...)
> 
> It probably can, but the unification can wait until the code are in.

The unification has to be done as a part of this series. Cleanups are
part of the development process of new code and not an optional
feature.

Thanks,

	tglx

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