linux-kernel - Re: [tip:timers/urgent] hrtimer: Fix /proc/timer

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Message-ID: <alpine.LFD.2.00.0911191053390.24119@localhost.localdomain>
Date:	Thu, 19 Nov 2009 11:05:17 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Ingo Molnar <mingo@...e.hu>
cc:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, heiko.carstens@...ibm.com,
	feng.tang@...el.com, Fr??d??ric Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:timers/urgent] hrtimer: Fix /proc/timer_list regression

On Thu, 19 Nov 2009, Ingo Molnar wrote:
> i've bisected back to it:
> 
> | 887a29f59b93cf54e21814869a4ab6e80b6fa623 is the first bad commit
> | commit 887a29f59b93cf54e21814869a4ab6e80b6fa623
> | Author: Feng Tang <feng.tang@...el.com>
> | Date:   Thu Sep 3 16:32:53 2009 +0800
> |
> |    hrtimer: Fix /proc/timer_list regression
> 
> Config attached.
> 
> I've removed it from timers/urgent for now.

Come on, this is a patently wrong conclusion.

We call timer_stats_update_stats() which returns on top of the
function due to:

	if (likely(!timer_stats_active))
		return;

timer_stats_active is 0 during boot and you can only activate it by
writing to /proc/timer_stats which you certainly did not at this
point.

Can you please explain how a call to a function which returns right
away can cause that problem ? 

That patch unearthed some other bug and your revert is just papering
over that fact.

Thanks,

	tglx
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