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

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Message-ID: <56B2A749.8080400@huawei.com>
Date:	Thu, 4 Feb 2016 09:20:09 +0800
From:	Ding Tianhong <dingtianhong@...wei.com>
To:	Davidlohr Bueso <dave@...olabs.net>
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 2016/2/4 3:24, Davidlohr Bueso wrote:
> 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
> 

Hi Davidlohr, Peter:

According Davidlohr's suggestion, I use several VM to test Peter's patch, and sadly I found one VM
still happen Hung Task for this problem, so I think we still need to think more about this solution.

Thanks.
Ding

> .
>