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From: Mike Travis <travis@sgi.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Andi Kleen <ak@suse.de>, Christoph Lameter <clameter@sgi.com>,
	jeremy@goop.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/3] percpu: Optimize percpu accesses
Date: Tue, 29 Jan 2008 12:00:57 -0800	[thread overview]
Message-ID: <479F85F9.3040104@sgi.com> (raw)
In-Reply-To: <20080124224613.GA24855@elte.hu>

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

WARNING: multiple messages have this Message-ID (diff)
From: Mike Travis <travis@sgi.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Andi Kleen <ak@suse.de>, Christoph Lameter <clameter@sgi.com>,
	jeremy@goop.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/3] percpu: Optimize percpu accesses
Date: Tue, 29 Jan 2008 12:00:57 -0800	[thread overview]
Message-ID: <479F85F9.3040104@sgi.com> (raw)
In-Reply-To: <20080124224613.GA24855@elte.hu>

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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  parent reply	other threads:[~2008-01-29 20:01 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-23  4:49 [PATCH 0/3] percpu: Optimize percpu accesses travis
2008-01-23  4:49 ` travis
2008-01-23  4:49 ` [PATCH 1/3] generic: Percpu infrastructure to rebase the per cpu area to zero travis
2008-01-23  4:49   ` travis
2008-01-23  4:49 ` [PATCH 2/3] x86_64: Fold pda into per cpu area travis
2008-01-23  4:49   ` travis
2008-01-23  4:49 ` [PATCH 3/3] x86_64: Rebase per cpu variables to zero travis
2008-01-23  4:49   ` travis
2008-01-24 22:46 ` [PATCH 0/3] percpu: Optimize percpu accesses Ingo Molnar
2008-01-25  0:17   ` Mike Travis
2008-01-25  0:25     ` Ingo Molnar
2008-01-25  0:25       ` Ingo Molnar
2008-01-25  0:58       ` Mike Travis
2008-01-25  0:58         ` Mike Travis
2008-01-25  1:18         ` Jeremy Fitzhardinge
2008-01-25  1:18           ` Jeremy Fitzhardinge
2008-01-25  1:46         ` Jeremy Fitzhardinge
2008-01-25  1:46           ` Jeremy Fitzhardinge
2008-01-29 20:00   ` Mike Travis [this message]
2008-01-29 20:00     ` Mike Travis
2008-01-29 20:13     ` Christoph Lameter
2008-01-29 20:13       ` Christoph Lameter

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