linux-kernel - Re: [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes

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Message-ID: <4910EDCF.2050206@zytor.com>
Date:	Tue, 04 Nov 2008 16:50:23 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	Alexander van Heukelum <heukelum@...tmail.fm>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Alexander van Heukelum <heukelum@...lshack.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>, lguest@...abs.org,
	jeremy@...source.com, Steven Rostedt <srostedt@...hat.com>,
	Mike Travis <travis@....com>
Subject: Re: [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes

Jeremy Fitzhardinge wrote:
> Andi Kleen wrote:
>> ???  LOCK slowness is not because of the bus. And I know you know that
>> Ingo, so I don't know why you wrote that bogosity above.
>>   
> 
> Why are the accesses locked?  Is it because it does an update of the
> accessed bit in the descriptor?  (We should be pre-setting them all
> anyway.)
> 

It is, but the locked access is unconditional.  Similar to any other
read/modify/write transaction -- the write is required to release the lock.

	-hpa
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