Re: Does smp_reschedule_interrupt really reschedule?

[Ingo Molnar <mingo@elte.hu>]

* Steven Rostedt <rostedt@goodmis.org> wrote:

> In finish_task_switch, we have:
> 
> #if defined(CONFIG_PREEMPT_RT) && defined(CONFIG_SMP)
> 	/*
> 	 * If we pushed an RT task off the runqueue,
> 	 * then kick other CPUs, they might run it:
> 	 */
> 	if (unlikely(rt_task(current) && prev->array && rt_task(prev))) {
> 		rt_overload_schedule++;
> 		smp_send_reschedule_allbutself();
> 	}
> #endif
> 
> 
> Here's my question, where does CPU1 get need_resched set?  As 
> discussed earlier, smp_send_reschedule_allbutself doesn't do it.

hm, you are right - the 'kick other CPUs' portion of RT-overload 
handling (which is a new scheduler feature currently being tested in the 
-RT kernel) is missing this step. So we might as well force a reschedule 
from the IPI handler - the way you suggested it. We might overdo 
scheduling a bit, but it cannot hurt - and it will definitely make a 
difference for the case where an RT task is waiting to be run.

the vanilla kernel is not affected.

	Ingo