Re: 2.6.17-rc6-rt3

[Ingo Molnar <mingo@elte.hu>]

* 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).

	Ingo