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SubjectRe: 2.4.4 sluggish under fork load
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> OK I found the explanation now. The reason ksoftirqd was deadlocking on
> me without the explicit clear of SCHED_YIELD in p->policy is because a
> softirq event was pending at the time of the first kernel_thread() and
> then while returning from the syscall it was so taking the ret_from_irq

Oh boy.

> > + current->policy |= SCHED_YIELD;
> > + current->need_resched = 1;
> > + }
>
> Alan, the patch you merged in 2.4.4ac2 can fail like mine, but it may fail in
> a much more subtle way, while I notice if ksoftirqd never get scheduled
> because I synchronize on it and I deadlock, your kupdate/bdflush/kswapd
> may be forked off correctly but they can all have SCHED_YIELD set and
> they will *never* get scheduled. You know what can happen if kupdate
> never gets scheduled... I recommend to be careful with 2.4.4ac2.

Change merged for -ac3. Nice debugging

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