lkml.org 
[lkml]   [2017]   [Feb]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: tip: demise of tsk_cpus_allowed() and tsk_nr_cpus_allowed()
On Mon, Feb 06, 2017 at 01:29:28PM +0100, Ingo Molnar wrote:
> > +/* Future-safe accessor for struct task_struct's cpus_allowed. */
> > +static inline const struct cpumask *tsk_cpus_allowed(struct task_struct *p)
> > +{
> > + if (__migrate_disabled(p))
> > + return cpumask_of(task_cpu(p));
> > +
> > + return &p->cpus_allowed;
> > +}
> > +
> > +static inline int tsk_nr_cpus_allowed(struct task_struct *p)
> > +{
> > + if (__migrate_disabled(p))
> > + return 1;
> > + return p->nr_cpus_allowed;
> > +}
>
> So ... I think the cleaner approach in -rt would be to introduce
> ->cpus_allowed_saved, and when disabling/enabling migration then saving the
> current mask there and changing ->cpus_allowed - and then restoring it when
> re-enabling migration.
>
> This means ->cpus_allowed could be used by the scheduler directly, no wrappery
> would be required, AFAICS.
>
> ( Some extra care would be required in places that change ->cpus_allowed because
> they'd now have to be aware of ->cpus_allowed_saved. )
>
> Am I missing something?

cpumasks are a pain, the above avoids allocating more of them.

\
 
 \ /
  Last update: 2017-02-06 14:33    [W:0.080 / U:0.264 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site