Re: 2.4.4 sluggish under fork load

["J . A . Magallon" <jamagallon@able.es>]

On 05.01 Andrea Arcangeli wrote:
> 
> And if you fork off a child with its p->policy SCHED_YIELD set it will
> never get scheduled in.
> 
> Only "just" running tasks can have SCHED_YIELD set.
> 
> So the below lines are the *right* and most robust approch as far I can
> tell. (plus counter needs to be volatile, as every variable that can
> change under the C code, even while it's probably not required by the
> code involved with current->counter)
> 
> > +	{
> > +		int counter = current->counter >> 1;
> > +		current->counter = p->counter = counter;
> > +		p->policy &= ~SCHED_YIELD;
> > +		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.
> 

It looks like this is related to my problem (see thread [Re: Linux-2.4.4-ac2]).
Funtions __start_kernel called kernel_thread(init,...), and seems to hang
on cpu_idle().

-- 
J.A. Magallon                                          #  Let the source
mailto:jamagallon@able.es                              #  be with you, Luke... 

Linux werewolf 2.4.4-ac1 #1 SMP Tue May 1 11:35:17 CEST 2001 i686