linux-kernel - Re: [2.6.28-rc6] oprofile: "opcontrol --start" output two warnings

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Date:	Tue, 25 Nov 2008 12:09:35 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Robert Richter <robert.richter@....com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [2.6.28-rc6] oprofile: "opcontrol --start" output two warnings

> if so, I think get_stagger() is a bit strange.
> it depend on caller cpu. then if PREEMPT=Y, it return radom result.

Even without PREEMPT it is random because there is no guarantee the
init code is executing on CPU 0

> 
> I'm not sure about oprofile design.
> but if you are right, I think p4_fill_in_addresses shoudn't use smp_processor_id().

Correct.

> 
> Am I missing any point?

No you're right. Always returning 0 in get_stagger() should be ok
I think, at least it wouldn't make anything worse.

Or perhaps figure out if the per cpu addresses are really needed,
if yes then this would need much more changes. But I hope 
that would not be needed.

But someone should better test it, the P4 perfmon handling is certainly
hairy and I don't claim to understand all its intricate details.

-Andi

-- 
ak@...ux.intel.com
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