linux-kernel - Re: [PATCH 2/4] locking/rtmutex: Use cmp-cmpxchg

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Message-ID: <CAGQ1y=5GqtK_yvK_uwn2exOQxD20DhLUNtrQ0BokPZaRvCJxKw@mail.gmail.com>
Date:	Mon, 15 Jun 2015 18:00:23 -0700
From:	Jason Low <jason.low2@...com>
To:	Davidlohr Bueso <dave@...olabs.net>
Cc:	Jason Low <jason.low2@...com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] locking/rtmutex: Use cmp-cmpxchg

On Mon, Jun 15, 2015 at 12:37 PM, Davidlohr Bueso <dave@...olabs.net> wrote:
> On Mon, 2015-06-15 at 11:34 -0700, Jason Low wrote:
>> The CCAS technique was typically used in the slow paths for those
>> other locks, where the chance of the operation returning false is
>> higher.
>
> That is true. Although I really want to use it in patch 4, I guess I
> could move the check in there, and thus avoid having it in the fastpath.

I agree, that way, we only have the extra check in cases where it is
beneficial, like in the optimistic spin loop.

Jason
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