Messages in this thread | | | Date | Mon, 6 Feb 2017 14:32:42 +0100 | From | Peter Zijlstra <> | Subject | Re: 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.
| |