From: Waiman Long <waiman.long@hp.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Scott J Norton <scott.norton@hp.com>,
Douglas Hatch <doug.hatch@hp.com>,
Davidlohr Bueso <dave@stgolabs.net>
Subject: Re: [PATCH v3 1/7] locking/pvqspinlock: Unconditional PV kick with _Q_SLOW_VAL
Date: Fri, 31 Jul 2015 13:01:13 -0400 [thread overview]
Message-ID: <55BBA9D9.9030302@hp.com> (raw)
In-Reply-To: <20150731083920.GD19282@twins.programming.kicks-ass.net>
On 07/31/2015 04:39 AM, Peter Zijlstra wrote:
> On Wed, Jul 22, 2015 at 04:12:36PM -0400, Waiman Long wrote:
>> The smp_store_release() is not a full barrier. In order to avoid missed
>> wakeup, we may need to add memory barrier around locked and cpu state
>> variables adding to complexity. As the chance of spurious wakeup is very
>> low, it is easier and safer to just do an unconditional kick at unlock
>> time.
> This needs to better spell out the race; my still sleeping brain doesn't
> want to co-operate and its generally better to spell out these things
> anyway.
Sure, I will add a comment to talk about the possible race.
Cheers,
Longman
next prev parent reply other threads:[~2015-07-31 17:01 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-22 20:12 [PATCH v3 0/7] locking/qspinlock: Enhance pvqspinlock performance Waiman Long
2015-07-22 20:12 ` [PATCH v3 1/7] locking/pvqspinlock: Unconditional PV kick with _Q_SLOW_VAL Waiman Long
2015-07-25 22:31 ` Davidlohr Bueso
2015-07-27 1:46 ` Davidlohr Bueso
2015-07-27 17:50 ` Waiman Long
2015-07-27 18:41 ` Davidlohr Bueso
2015-07-31 8:39 ` Peter Zijlstra
2015-07-31 17:01 ` Waiman Long [this message]
2015-07-22 20:12 ` [PATCH v3 2/7] locking/pvqspinlock: Add pending bit support Waiman Long
2015-07-26 23:09 ` Davidlohr Bueso
2015-07-27 17:11 ` Waiman Long
2015-07-26 23:48 ` Davidlohr Bueso
2015-07-27 0:56 ` Davidlohr Bueso
2015-07-27 17:30 ` Waiman Long
2015-07-27 19:39 ` Davidlohr Bueso
2015-07-29 20:49 ` Waiman Long
2015-07-27 20:08 ` Davidlohr Bueso
2015-07-22 20:12 ` [PATCH v3 3/7] locking/pvqspinlock: Collect slowpath lock statistics Waiman Long
2015-07-27 1:14 ` Davidlohr Bueso
2015-07-27 17:33 ` Waiman Long
2015-07-22 20:12 ` [PATCH v3 4/7] locking/pvqspinlock: Enable deferment of vCPU kicking to unlock call Waiman Long
2015-07-22 20:12 ` [PATCH v3 5/7] locking/pvqspinlock: Allow vCPUs kick-ahead Waiman Long
2015-07-22 20:12 ` [PATCH v3 6/7] locking/pvqspinlock: Queue node adaptive spinning Waiman Long
2015-07-22 20:12 ` [PATCH v3 7/7] locking/pvqspinlock, x86: Optimize PV unlock code path Waiman Long
2015-07-27 1:18 ` [PATCH v3 0/7] locking/qspinlock: Enhance pvqspinlock performance Davidlohr Bueso
2015-07-27 17:36 ` Waiman Long
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