Hi, On 05/11/14 08:51, Wanpeng Li wrote: > I observe that dl task can't be migrated to other cpus during cpu hotplug, in > addition, task may/may not be running again if cpu is added back. The root > cause > which I found is that dl task will be throtted and removed from dl rq after > comsuming all budget, which leads to stop task can't pick it up from dl rq and > migrate to other cpus during hotplug. > > The method to reproduce: > schedtool -E -t 50000:100000 -e ./test > Actually test is just a simple for loop. Then observe which cpu the test > task is on. > echo 0 > /sys/devices/system/cpu/cpuN/online > > This patch fix it by push the task to another cpu in dl_task_timer() if > rq is offline. > > Note: dl task can be migrated successfully if rq is offline currently, > however, > I'm still not sure why task_rq(task)->rd->span just include the cpu which the > dl > task previous running on, so cpu_active_mask is used in the patch. > > Peterz, Juri? > > Signed-off-by: Wanpeng Li <wanpeng...@linux.intel.com> > --- > v1 -> v2: > * push the task to another cpu in dl_task_timer() if rq is offline. > > kernel/sched/deadline.c | 39 ++++++++++++++++++++++++++++++++++++--- > 1 file changed, 36 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index 04c2cbb..233e482 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -487,6 +487,7 @@ static int start_dl_timer(struct sched_dl_entity *dl_se, > bool boosted) > return hrtimer_active(&dl_se->dl_timer); > } > > +static struct rq *find_lock_later_rq(struct task_struct *task, struct rq > *rq); > /* > * This is the bandwidth enforcement timer callback. If here, we know > * a task is not on its dl_rq, since the fact that the timer was running > @@ -538,6 +539,39 @@ again: > update_rq_clock(rq); > dl_se->dl_throttled = 0; > dl_se->dl_yielded = 0; > + > + /* > + * So if we find that the rq the task was on is no longer > + * available, we need to select a new rq. > + */ > + if (!rq->online) { > + struct rq *later_rq = NULL; > + > + /* We will release rq lock */ > + get_task_struct(p); > + > + raw_spin_unlock(&rq->lock); > + > + later_rq = find_lock_later_rq(p, rq); > + > + if (!later_rq) { > + put_task_struct(p); > + goto out; > + } > + > + deactivate_task(rq, p, 0); > + set_task_cpu(p, later_rq->cpu); > + activate_task(later_rq, p, 0); > + > + resched_curr(later_rq); > + > + double_unlock_balance(rq, later_rq); > + > + put_task_struct(p); > + > + goto out; > + } > + > if (task_on_rq_queued(p)) { > enqueue_task_dl(rq, p, ENQUEUE_REPLENISH); > if (dl_task(rq->curr)) > @@ -555,7 +589,7 @@ again: > } > unlock: > raw_spin_unlock(&rq->lock); > - > +out: > return HRTIMER_NORESTART; > } > > @@ -1182,8 +1216,7 @@ static int find_later_rq(struct task_struct *task) > * We have to consider system topology and task affinity > * first, then we can look for a suitable cpu. > */ > - cpumask_copy(later_mask, task_rq(task)->rd->span); > - cpumask_and(later_mask, later_mask, cpu_active_mask); > + cpumask_copy(later_mask, cpu_active_mask);
I fear this breaks what I lately fixed in commit 91ec6778ec4f ("sched/deadline: Fix inter- exclusive cpusets migrations"), as we first have to consider exclusive cpusets topology in looking for a cpu. But, I'd have to test this to see if I'm right, and I'll try to do it soon. Thanks, - Juri > cpumask_and(later_mask, later_mask, &task->cpus_allowed); > best_cpu = cpudl_find(&task_rq(task)->rd->cpudl, > task, later_mask); > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/