linux-kernel - RE: [PATCH v4 1/7] locking/pvqspinlock: Unconditional PV kick with _Q_SLOW

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Message-ID: <401F72D6D1DFE3499766D25AA4EED18A440D6B10@G2W2529.americas.hpqcorp.net>
Date:	Sat, 1 Aug 2015 20:12:34 +0000
From:	"Long, Wai Man" <waiman.long@...com>
To:	Davidlohr Bueso <dave@...olabs.net>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Norton, Scott J" <scott.norton@...com>,
	"Hatch, Douglas B (HPS Linux PM)" <doug.hatch@...com>
Subject: RE: [PATCH v4 1/7] locking/pvqspinlock: Unconditional PV kick with
 _Q_SLOW_VAL

Davidlohr,

I am sorry that I forgot to put in your tag.

Cheers,
Longman

-----Original Message-----
From: linux-kernel-owner@...r.kernel.org [mailto:linux-kernel-owner@...r.kernel.org] On Behalf Of Davidlohr Bueso
Sent: Saturday, August 01, 2015 2:01 PM
To: Long, Wai Man
Cc: Peter Zijlstra; Ingo Molnar; Thomas Gleixner; H. Peter Anvin; x86@...nel.org; linux-kernel@...r.kernel.org; Norton, Scott J; Hatch, Douglas B (HPS Linux PM)
Subject: Re: [PATCH v4 1/7] locking/pvqspinlock: Unconditional PV kick with _Q_SLOW_VAL

On Fri, 2015-07-31 at 22:21 -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.
> 
> Signed-off-by: Waiman Long <Waiman.Long@...com>

Please keep tags from previous versions ;)

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