On 7/22/19 2:28 PM, Juri Lelli wrote: > On 22/07/19 13:07, Dietmar Eggemann wrote: >> On 7/19/19 3:59 PM, Juri Lelli wrote: >> >> [...] >> >>> @@ -557,6 +558,38 @@ static struct rq *dl_task_offline_migration(struct rq *rq, struct task_struct *p >>> double_lock_balance(rq, later_rq); >>> } >>> >>> + if (p->dl.dl_non_contending || p->dl.dl_throttled) { >>> + /* >>> + * Inactive timer is armed (or callback is running, but >>> + * waiting for us to release rq locks). In any case, when it >>> + * will file (or continue), it will see running_bw of this >> >> s/file/fire ? > > Yep. > >>> + * task migrated to later_rq (and correctly handle it). >> >> Is this because of dl_task_timer()->enqueue_task_dl()->task_contending() >> setting dl_se->dl_non_contending = 0 ? > > No, this is related to inactive_task_timer() callback. Since the task is > migrated (by this function calling set_task_cpu()) because a CPU hotplug > operation happened, we need to reflect this w.r.t. running_bw, or > inactive_task_timer() might sub from the new CPU and cause running_bw to > underflow. I was more referring to the '... it will see running_bw of thus task migrated to later_rq ...) and specifically to the HOW the timer callback can detect this. I should have made this clearer. inactive_task_timer() checks if (dl_se->dl_non_contending == 0) so I thought I have to find the place where dl_se->dl_non_contending is set 0?