Re: [PATCH 2.6.12-rc5-mm2] [sched] add allowed CPUs check into find_idlest_group()

[M.Baris Demiray]

Nick Piggin wrote:
> M.Baris Demiray wrote:
> [...]
> > But, isn't it required for us to be allowed to run on _every_
> > CPU in that group. If we take intersection and continue if
> > that's not empty, then there could be CPUs in group that are
> > not allowed. Since any CPU then can be the idlest in that
> > group we can be assigned to a CPU that is not allowed.
> > Missing something?
>
> That should be OK. We basically aren't too interested in
> exactly which CPU it should go to, but just that it should
> go to that group.
>
> If the group is determined to be the idlest, and there is
> a CPU that can run the task, then that's all we need.

OK. And also I missed the point that you requested a second check
in find_idlest_cpu() which'll prevent an assignment to an unallowed
CPU. That will solve the problem.

> [...]
> > Meanwhile, what is the problem with that patch? Not traversing
> > the CPUs correctly or continue;ing is wrong?
> >
> >     for_each_cpu_mask(i, group->cpumask) {
> >         if (!cpu_isset(i, p->cpus_allowed))
> >             continue;
> >     }
>
> In Linux, the for_* macros actually *are* for loops. So that is
> that loop that your continue continues, and seeing as it is at
> the end of that for loop, it does nothing.

Argh. I'll look at these.

Thanks Nick.

> Thanks,
> Nick

--
"You have to understand, most of these people are not ready to be
unplugged. And many of them are no inert, so hopelessly dependent
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