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SubjectRe: 2.6.17-rc6-rt3

* 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
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