About EDF SMP Behaviour

[Richi Dubey]

I understand. Thanks for the quick response!

On Mon, May 17, 2021 at 11:58 AM Sebastian Huber <
sebastian.huber at embedded-brains.de> wrote:

>
>
> On 17/05/2021 08:17, Richi Dubey wrote:
> >
> > Can someone please explain this behavior of EDF SMP Scheduler on a 4 CPU
> > system, with INIT task pinned to cpu 0:
> >
> >
> > Before Task 3 (Priority 6, Affined to CPU 3) arrival:
> >
> > CPU 1 is executing: Task 1 (Priority 5, Affined to CPU 1)
> > CPU 2 is executing: Task 2 (Priority 7, Affined to CPU 2)
> > CPU 3 is executing: Task 0 (Priority 3, Affined to ALL)
> >
> > After Task 3 arrival:
> > CPU 1 is executing: Task 1 (Priority 5, Affined to CPU 1)
> > CPU 2 is executing: Task 0 (Priority 3, Affined to ALL)
> > CPU 3 is executing: Task 3 (Priority 6, Affined to CPU 3)
> >
> > How did Task 3 force Task 0 out of its CPU when Task 0 has a higher
> > priority?
>
> Task 0 still has a processor, it just moved from CPU 3 to 2. Task 3 can
> only use CPU 3.
>
> > Is thread helping involved?
>
> No, thread helping is only involved if you use mutexes.
>
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