linux-kernel - Re: [patch] hrtimers debug patch

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Message-ID: <20070406163927.GA27031@elte.hu>
Date:	Fri, 6 Apr 2007 18:39:27 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Michal Piotrowski <michal.k.k.piotrowski@...il.com>
Cc:	Nick Piggin <npiggin@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Mingming Cao <cmm@...ibm.com>, Adrian Bunk <bunk@...sta.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Mariusz Kozlowski <m.kozlowski@...land.pl>,
	Oliver Pinter <oliver.pntr@...il.com>,
	Sid Boyce <g3vbv@...eyonder.co.uk>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [patch] hrtimers debug patch


* Michal Piotrowski <michal.k.k.piotrowski@...il.com> wrote:

> > thanks! I have stared at hrtimer.c a few more hours and the good 
> > news is that i found a narrow SMP race. The bad news is that i dont 
> > think it could explain your bug symptoms: the worst-case effect of 
> > the race should be an incorrect timeout on the current CPU - not a 
> > KTIME_MAX thing like your logs show.
> >
> > But maybe i didnt think through the effects of the bug well enough, 
> > and your box has a HT CPU, with HT CPUs being pretty good at 
> > triggering narrow SMP races - so maybe we are lucky? Fix attached 
> > below. Patch is build and boot-tested.
> 
> I didn't see this weird hang for 12 days. I think that this patch 
> solves this issue.

cool :)

> Huge thans!

huge thanks to you for testing it!

	Ingo
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