On Wed, Aug 18, 2021 at 11:42:28AM +0100, Will Deacon wrote:
> As for your other suggestion:
>
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -2733,6 +2733,7 @@ static int __set_cpus_allowed_ptr_locked
> > const struct cpumask *cpu_allowed_mask = task_cpu_possible_mask(p);
> > const struct cpumask *cpu_valid_mask = cpu_active_mask;
> > bool kthread = p->flags & PF_KTHREAD;
> > + struct cpumask *user_mask = NULL;
> > unsigned int dest_cpu;
> > int ret = 0;
> >
> > @@ -2792,9 +2793,13 @@ static int __set_cpus_allowed_ptr_locked
> > __do_set_cpus_allowed(p, new_mask, flags);
> >
> > if (flags & SCA_USER)
> > - release_user_cpus_ptr(p);
> > + swap(user_mask, p->user_cpus_ptr);
> > +
> > + ret = affine_move_task(rq, p, rf, dest_cpu, flags);
> > +
> > + kfree(user_mask);
> >
> > - return affine_move_task(rq, p, rf, dest_cpu, flags);
> > + return ret;
> >
> > out:
> > task_rq_unlock(rq, p, rf);
> > @@ -2954,8 +2959,10 @@ void relax_compatible_cpus_allowed_ptr(s
> > return;
> >
> > raw_spin_lock_irqsave(&p->pi_lock, flags);
> > - release_user_cpus_ptr(p);
> > + p->user_cpus_ptr = NULL;
> > raw_spin_unlock_irqrestore(&p->pi_lock, flags);
> > +
> > + kfree(mask);
>
> I think the idea looks good, but perhaps we could wrap things up a bit:
>
> /* Comment about why this is useful with RT */
> static cpumask_t *clear_user_cpus_ptr(struct task_struct *p)
> {
> struct cpumask *user_mask = NULL;
>
> swap(user_mask, p->user_cpus_ptr);
> return user_mask;
> }
>
> void release_user_cpus_ptr(struct task_struct *p)
> {
> kfree(clear_user_cpus_ptr(p));
> }
>
> Then just use clear_user_cpus_ptr() in sched/core.c where we know what
> we're doing (well, at least one of us does!).
OK, I'll go make it like that.
