linux-kernel - Re: [PATCH] locking/mutex: Avoid spinner vs waiter starvation

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Message-ID: <20160203192458.GA26475@linux-uzut.site>
Date:	Wed, 3 Feb 2016 11:24:58 -0800
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Ding Tianhong <dingtianhong@...wei.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Waiman Long <waiman.long@....com>,
	Jason Low <jason.low2@...com>, Ingo Molnar <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Will Deacon <Will.Deacon@....com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Waiman Long <Waiman.Long@...com>
Subject: Re: [PATCH] locking/mutex: Avoid spinner vs waiter starvation

On Wed, 03 Feb 2016, Ding Tianhong wrote:

>Agree, but this patch is going to help the waiter in the wait list to get the lock, your scene probability looks more
>too low and I don't think it is a problem.

Sure, I was in fact implying its not the end of the world,
although it will be interesting to see the impact on different
(non pathological) workloads, even if it only affects a single
waiter. Also, technically this issue can also affect rwsems if
only using writers, but that's obviously pretty idiotic, so I
wouldn't worry about it.

Thanks,
Davidlohr