Hi Kirill, I'll try to read this series later, just one silly question for now.
On 07/26, Kirill Tkhai wrote: > > Patch [2/5] is main in the series. It introduces new state: ONRQ_MIGRATING > and teaches scheduler to understand it (we need a little changes predominantly > in try_to_wake_up()). This will be used in the following way: > > (we are changing task's rq) > > raw_spin_lock(&src_rq->lock); > dequeue_task(src_rq, p, 0); > p->on_rq = ONRQ_MIGRATING; > set_task_cpu(p, dst_cpu); > raw_spin_unlock(&src_rq->lock); > > raw_spin_lock(&dst_rq->lock); > p->on_rq = ONRQ_QUEUED; > enqueue_task(dst_rq, p, 0); > raw_spin_unlock(&dst_rq->lock); Hmm. And what if the code above doesn't hold p->pi_lock (4/5) and, say, __sched_setscheduler() does fair_sched_class->rt_sched_class transition in between? ONRQ_MIGRATING helps to avoid the wrong dequeue + enqueue, but I am not sure about check_class_changed(). Say, switched_from_fair() will use dst_rq even if p was never queued on this rq... This only affects the .decay_count logic, perhaps this is fine, I simply do not know what this code does. What about switched_to_rt() ? we lose the push_rt_task() logic... Hmm, which I can't understand too ;) And we also lose ENQUEUE_HEAD in this case, but this looks fine. In short: could you confirm there are no problems here? Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
