linux-kernel - Re: [PATCH RFC 6/6] Implement "current" with the PDA.

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Message-Id: <200608271801.16406.ak@suse.de>
Date:	Sun, 27 Aug 2006 18:01:16 +0200
From:	Andi Kleen <ak@...e.de>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	linux-kernel@...r.kernel.org,
	Chuck Ebbert <76306.1226@...puserve.com>,
	Zachary Amsden <zach@...are.com>,
	Jan Beulich <jbeulich@...ell.com>,
	Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH RFC 6/6] Implement "current" with the PDA.

On Sunday 27 August 2006 10:44, Jeremy Fitzhardinge wrote:
> Use the pcurrent field in the PDA to implement the "current" macro.
> This ends up compiling down to a single instruction to get the current
> task.
> 
> The slightly tricky part about this patch is that cpu_init() uses
> current very early, before the PDA has been set up.  In this instance,
> it uses current_thread_info()->task to get the current task.
> 
> Also, the very early PDA set up for the boot cpu contains the initial
> task pointer so current works from a very early stage.

With that you could remove the code in do_IRQ now that setups up a fake thread_info
for interrupt stacks.

-Andi
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