Re: [RFC] Repeated rto_push_irq_work_func() invocation.

[Sebastian Andrzej Siewior]

On 2024-10-02 10:37:49 [-0400], Steven Rostedt wrote:
> On Wed, 2 Oct 2024 13:21:05 +0200
> Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote:
> 
> > Would it make sense to avoid scheduling rto_push_work if rq->curr has
> > NEED_RESCHED set and make the scheduler do push_rt_task()?
> 
> Can we safely check rq->curr without taking any locks on that CPU?
> 
> I guess tasks do not get freed while a CPU has preemption disabled, so it
> may be safe to do:
> 
> 	task = READ_ONCE(rq->curr);
> 	if (test_task_need_resched(task))
> 		/* skip */
> 
> ??

+rcu_read_lock() but yes. This would be one part. You need to check if
the task on pull-list has lower priority than the current task on rq.
This would be need to be moved to somewhere in schedule() probably after
pick_next_task().

> -- Steve

Sebastian