linux-kernel - Re: [PATCH 1/4, v2] x86: enlightenment for ticket spin locks

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Date:	Wed, 30 Jun 2010 12:54:57 +0100
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	"Peter Zijlstra" <peterz@...radead.org>
Cc:	"mingo@...e.hu" <mingo@...e.hu>,
	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"Ky Srinivasan" <KSrinivasan@...ell.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"hpa@...or.com" <hpa@...or.com>
Subject: Re: [PATCH 1/4, v2] x86: enlightenment for ticket spin locks -
	 base implementation

>>> On 30.06.10 at 13:48, Peter Zijlstra <peterz@...radead.org> wrote:
> On Wed, 2010-06-30 at 12:43 +0100, Jan Beulich wrote:
> 
>> It does tickle just the new owner - that's what the list is for.
> 
> But if you have a FIFO list you don't need the ticket stuff and can
> implement a FIFO lock instead.

The list is LIFO (not FIFO, as only the most recently added entry is
a candidate for needing wakeup as long as there's no interrupt
re-enabling in irqsave lock paths), and is only used for tickling (not
for deciding who's going to be the next owner).

Jan

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