linux-kernel - Re: [RFC][PATCH 0/5] preempt

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Date:	Wed, 14 Aug 2013 09:58:07 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Mike Galbraith <bitbucket@...ine.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [RFC][PATCH 0/5] preempt_count rework

On 08/14/2013 09:52 AM, Peter Zijlstra wrote:
> 
> Oh curses, this is because lea can't do segment offsets? So there's no
> sane way to get addresses of per-cpu variables.
> 
> Because ideally we'd have something like:
> 
>   lea %gs:__percpu_runqueues,%rax
> 
> So in this case it makes sense to also store the actual pointer; how
> unfortunate.
> 

Correct; the segment offset is not part of the effective address, even
in 64-bit mode.

	-hpa

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