On Fri, Apr 13, 2018 at 10:26:48AM +0200, Peter Zijlstra wrote:
> On Mon, Apr 09, 2018 at 05:56:09PM +0100, Patrick Bellasi wrote:
> > +static inline void uclamp_cpu_get(struct task_struct *p, int cpu, int 
> > clamp_id)
> > +{
> > +   struct uclamp_cpu *uc_cpu = &cpu_rq(cpu)->uclamp[clamp_id];
> 
> > +static inline void uclamp_cpu_put(struct task_struct *p, int cpu, int 
> > clamp_id)
> > +{
> > +   struct uclamp_cpu *uc_cpu = &cpu_rq(cpu)->uclamp[clamp_id];
> 
> That all seems daft, since you already have rq at the call site.
> 
> > +static inline void uclamp_task_update(struct rq *rq, struct task_struct *p)
> > +{
> > +   int cpu = cpu_of(rq);
> > +   int clamp_id;
> > +
> > +   /* The idle task does not affect CPU's clamps */
> > +   if (unlikely(p->sched_class == &idle_sched_class))
> > +           return;
> > +   /* DEADLINE tasks do not affect CPU's clamps */
> > +   if (unlikely(p->sched_class == &dl_sched_class))
> > +           return;
> 
> This is wrong; it misses the stop_sched_class.
> 
> And since you're looking at sched_class anyway, maybe put a marker in
> there:
> 
>       if (!p->sched_class->has_clamping)
>               return;

Alternatively, we could simply add uclamp_task_{en,de}queue() into
{en,de}queue_task_{fair,rt}().

> > +   for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) {
> > +           if (uclamp_task_affects(p, clamp_id))
> > +                   uclamp_cpu_put(p, cpu, clamp_id);
> > +           else
> > +                   uclamp_cpu_get(p, cpu, clamp_id);
> > +   }
> > +}

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