linux-kernel - Re: [PATCH v4 3/3] locking/mutex: Ensure forward progress of waiter-spinner

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Date:	Wed, 10 Aug 2016 13:51:14 -0400
From:	Waiman Long <waiman.long@....com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Ingo Molnar <mingo@...hat.com>, <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ding Tianhong <dingtianhong@...wei.com>,
	Jason Low <jason.low2@....com>,
	Davidlohr Bueso <dave@...olabs.net>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Will Deacon <Will.Deacon@....com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Imre Deak <imre.deak@...el.com>
Subject: Re: [PATCH v4 3/3] locking/mutex: Ensure forward progress of waiter-spinner

On 08/10/2016 05:29 AM, Peter Zijlstra wrote:
> On Tue, Aug 09, 2016 at 02:00:00PM -0400, Waiman Long wrote:
>>> Alternative might be to use the LSB of mutex::owner, but that's going to
>>> be somewhat icky too.
>> I was thinking about doing that. However, the owner field is used in quite a
>> number of places. It may be a bit risky to change all of them.
> Agreed.
>

It will be easier to do that for rwsem as the owner field isn't used for 
the debug code, unlike the mutex.

Cheers,
Longman