linux-kernel - Re: [PATCH 0/3] percpu: Optimize percpu accesses

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Message-ID: <479F85F9.3040104@sgi.com>
Date:	Tue, 29 Jan 2008 12:00:57 -0800
From:	Mike Travis <travis@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Andrew Morton <akpm@...ux-foundation.org>, Andi Kleen <ak@...e.de>,
	Christoph Lameter <clameter@....com>, jeremy@...p.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] percpu: Optimize percpu accesses

Ingo Molnar wrote:
...
> 
> tried it on x86.git and 1/3 did not build and 2/3 causes a boot hang 
> with the attached .config.
> 
> 	Ingo
> 

I've tracked down the failure to an early printk that when CONFIG_PRINTK_TIME
is enabled, any early printks cause cpu_clock to be called, which accesses
cpu_rq which is defined as:

 595 #define cpu_rq(cpu)             (&per_cpu(runqueues, (cpu)))

Since the zero-based patch is changing the offset from one based on
__per_cpu_start to zero, it's causing the function to access a
different area.

I'm working on a fix now.

Thanks,
Mike
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