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Subject: Re: 2.6.17-rc6-rt3
From: =?ISO-8859-1?Q?S=E9bastien_Dugu=E9?= <sebastien.dugue@bull.net>
To: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>
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Date: Mon, 12 Jun 2006 11:35:08 +0200
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On Mon, 2006-06-12 at 11:20 +0200, Ingo Molnar wrote:
> * Sébastien Dugué <sebastien.dugue@bull.net> wrote:
> 
> > > I think all of the regressions reported against rt1 are fixed, please 
> > > re-report if any of them is still unfixed.
> > 
> >   Great, boots fine on my dual Xeon and solves the ping problem I was 
> > having.
> > 
> >   Thomas, any hint at what was going on?
> 
> the problem was caused by a mismerge of the __raise_softirq_irqoff() 
> changes of preempt-softirqs. In PREEMPT_SOFTIRQS, softirq activation 
> means a wakeup of the softirq thread - hence __raise_softirq_irqoff() 
> must wake up the softirq thead too. This didnt happen in -rt1 so the 
> network softirq (which processes things like ping reply packets) got 
> delayed to the natural softirq event - the next timer interrupt in the 
> usual case. Hence depending on HZ you got a delay of 1-4-10 msecs 
> (divided into two parts).
> 

  Thanks.

  Sébastien.