On Wed, 5 Jul 2017, Peter Zijlstra wrote:
> On Tue, Jul 04, 2017 at 10:20:23PM +0200, Thomas Gleixner wrote:
> > @@ -775,23 +787,13 @@ void notify_cpu_starting(unsigned int cp
>
> The comment right above this function now seems stale..
Will fix.
> > void cpuhp_online_idle(enum cpuhp_state state)
> > {
> > struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
> > - unsigned int cpu = smp_processor_id();
> >
> > /* Happens for the boot cpu */
> > if (state != CPUHP_AP_ONLINE_IDLE)
> > return;
> >
> > st->state = CPUHP_AP_ONLINE_IDLE;
> > -
> > - /* Unpark the stopper thread and the hotplug thread of this cpu */
> > - stop_machine_unpark(cpu);
> > - kthread_unpark(st->thread);
> > -
> > - /* Should we go further up ? */
> > - if (st->target > CPUHP_AP_ONLINE_IDLE)
> > - __cpuhp_kick_ap_work(st);
> > - else
> > - complete(&st->done);
> > + complete(&st->done);
> > }
>
>
> OK, so if I get this right we do something like:
>
>
> BP AP
>
> bringup_cpu();
> __cpu_up() ------------> /* stuff */
> bringup_wait_for_ap()
> wait_for_completion();
> cpuhp_online_idle();
> <------------ complete(&st->done);
> unpark()
> while(1)
> do_idle();
actually I added after unpark():
kick_ap()
wait_for_completion()
So the AP will execute the online callbacks in its own hotplug thread.
> Where you moved the unpark() from the AP's idle thread to the BP's
> context and thus allow scheduling etc..
>
> Yes that should work fine I think.
Thanks,
tglx
