On Mon, Nov 14, 2016 at 03:57:21PM +0100, Peter Zijlstra wrote:
> On Wed, Nov 09, 2016 at 11:05:10AM -0800, Jacob Pan wrote:
> > static inline bool is_idle_task(const struct task_struct *p)
> > {
> > - return p->pid == 0;
> > + return !!(p->flags & PF_IDLE);
> > }
>
> > +void play_idle()
> > +{
> > + /*
> > + * Only FIFO tasks can disable the tick since they don't need the forced
> > + * preemption.
> > + */
> > + WARN_ON_ONCE(current->policy != SCHED_FIFO);
> > + WARN_ON_ONCE(current->nr_cpus_allowed != 1);
> > + WARN_ON_ONCE(!(current->flags & PF_KTHREAD));
> > + WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY));
> > + rcu_sleep_check();
> > +
> > + preempt_disable();
> > + current->flags |= PF_IDLE;
> > + do_idle();
> > + current->flags &= ~PF_IDLE;
>
> Whoops, that will clear PF_IDLE from the idle thread. Maybe do something
> like:
>
> unsigned int idle_flag = (~current->flags & PF_IDLE)
>
> current->flags |= PF_IDLE;
>
> current->flags ^= idle_flag;
>
> > +
> > + preempt_fold_need_resched();
> > + preempt_enable();
> > +}
> > +EXPORT_SYMBOL_GPL(play_idle);
n/m I cannot read, the actual idle loop below uses do_idle(), not
play_idle.
> > @@ -299,5 +313,7 @@ void cpu_startup_entry(enum cpuhp_state state)
> > #endif
> > arch_cpu_idle_prepare();
> > cpuhp_online_idle(state);
> > - cpu_idle_loop();
> > + while (1)
> > + do_idle();
> > +
> > }
