From: Waiman Long <waiman.long@hpe.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ding Tianhong <dingtianhong@huawei.com>,
Ingo Molnar <mingo@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
"Paul E. McKenney" <paulmck@us.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <Will.Deacon@arm.com>, Jason Low <jason.low2@hp.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Waiman Long <Waiman.Long@hp.com>
Subject: Re: [PATCH RFC] locking/mutexes: don't spin on owner when wait list is not NULL.
Date: Fri, 22 Jan 2016 08:41:41 -0500 [thread overview]
Message-ID: <56A23195.4000802@hpe.com> (raw)
In-Reply-To: <20160122085422.GO6357@twins.programming.kicks-ass.net>
On 01/22/2016 03:54 AM, Peter Zijlstra wrote:
> On Thu, Jan 21, 2016 at 06:02:34PM -0500, Waiman Long wrote:
>> This patch attempts to fix this live-lock condition by enabling the
>> a woken task in the wait list to enter optimistic spinning loop itself
>> with precedence over the ones in the OSQ. This should prevent the
>> live-lock
>> condition from happening.
>
> So I think having the top waiter going back in to contend on the OSQ is
> an excellent idea, but I'm not sure the wlh_spinning thing is important.
Yes, that is optional. I put it there just to make it is more likely for
the waiter spinner to get the lock. Without that, the chance will be
50/50 on average. I can certainly take that out.
> The OSQ itself is FIFO fair, and the waiters retain the wait_list
> position. So having the top wait_list entry contending on the OSQ
> ensures we cannot starve (I think).
>
> Also, as Davidlohr said, we cannot copy/paste this much code.
As I said in the previous mail, I do intend to refactor it before
sending out the official patch.
Cheers,
Longman
next prev parent reply other threads:[~2016-01-22 13:41 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-21 9:29 [PATCH RFC] locking/mutexes: don't spin on owner when wait list is not NULL Ding Tianhong
2016-01-21 21:23 ` Tim Chen
2016-01-22 2:41 ` Paul E. McKenney
2016-01-22 2:48 ` Davidlohr Bueso
2016-01-22 3:13 ` Paul E. McKenney
2016-01-21 23:02 ` Waiman Long
2016-01-22 6:09 ` Davidlohr Bueso
2016-01-22 13:38 ` Waiman Long
2016-01-22 16:46 ` Davidlohr Bueso
2016-01-25 2:23 ` [PATCH] locking/mutex: Allow next waiter lockless wakeup Davidlohr Bueso
2016-01-25 23:02 ` Waiman Long
2016-02-29 11:21 ` [tip:locking/core] " tip-bot for Davidlohr Bueso
2016-01-22 8:54 ` [PATCH RFC] locking/mutexes: don't spin on owner when wait list is not NULL Peter Zijlstra
2016-01-22 10:20 ` Jason Low
2016-01-22 10:53 ` Peter Zijlstra
2016-01-22 10:56 ` Peter Zijlstra
2016-01-22 11:06 ` Peter Zijlstra
2016-01-22 13:59 ` Waiman Long
2016-01-24 8:03 ` Ding Tianhong
2016-01-29 9:53 ` Peter Zijlstra
2016-01-30 1:18 ` Ding Tianhong
2016-02-01 3:29 ` huang ying
2016-02-01 3:35 ` Huang, Ying
2016-02-01 10:08 ` [PATCH] locking/mutex: Avoid spinner vs waiter starvation Peter Zijlstra
2016-02-02 21:19 ` Davidlohr Bueso
2016-02-03 7:10 ` Ding Tianhong
2016-02-03 19:24 ` Davidlohr Bueso
2016-02-04 1:20 ` Ding Tianhong
2016-02-12 18:33 ` Waiman Long
2016-02-03 22:07 ` Waiman Long
2016-02-04 1:35 ` Jason Low
2016-02-04 8:55 ` huang ying
2016-02-04 22:49 ` Jason Low
2016-01-22 13:41 ` Waiman Long [this message]
-- strict thread matches above, loose matches on Subject: below --
2016-01-21 6:53 [PATCH RFC ] locking/mutexes: don't spin on owner when wait list is not NULL Ding Tianhong
2016-01-21 7:29 ` Ingo Molnar
2016-01-21 9:04 ` Ding Tianhong
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