Re: [PATCH] sched: __set_cpus_allowed_ptr(): Check cpus_mask, not cpus_ptr

Sebastian Andrzej Siewior
2020-06-18T08:10:26Z

On 2020-06-17 17:49:48 [-0500], Scott Wood wrote:
> > Makes sense, but what about the rest of the checks? Further down there is
> >
> > /* Can the task run on the task's current CPU? If so, we're done
> > */
> > if (cpumask_test_cpu(task_cpu(p), new_mask))
> > goto out;
> >
> > If the task is currently migrate disabled and for some stupid reason it
> > gets affined elsewhere, we could try to move it out - which AFAICT we
> > don't
> > want to do because migrate disabled. So I suppose you'd want an extra
> > bailout condition here when the task is migrate disabled.
> >
> > ISTR in RT you do re-check the affinity and potentially move the task away
> > when re-enabling migration, so that should work out all fine.
>
> On RT the above test is:
>
> /* Can the task run on the task's current CPU? If so, we're done */
> if (cpumask_test_cpu(task_cpu(p), new_mask) ||
> p->cpus_ptr != &p->cpus_mask)
> goto out;
>
> ...so we do bail out if we're migrate disabled.

correct. There is a complete migrate_disable() patch in the RT queue
which has to wait. This patch however looked to be independent of that
and could "fix" the pointer part which is already here so I sent it.

> -Scott

Sebastian