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authorVincent Guittot <vincent.guittot@linaro.org>2020-03-06 09:42:08 +0100
committerIngo Molnar <mingo@kernel.org>2020-03-06 12:57:25 +0100
commit5ab297bab984310267734dfbcc8104566658ebef (patch)
tree51fbe5f5090fb7681cfb4d12612344afd944d30b /kernel/sched/fair.c
parent6212437f0f6043e825e021e4afc5cd63e248a2b4 (diff)
downloadlinux-5ab297bab984310267734dfbcc8104566658ebef.tar.gz
sched/fair: Fix reordering of enqueue/dequeue_task_fair()
Even when a cgroup is throttled, the group se of a child cgroup can still be enqueued and its gse->on_rq stays true. When a task is enqueued on such child, we still have to update the load_avg and increase h_nr_running of the throttled cfs. Nevertheless, the 1st for_each_sched_entity() loop is skipped because of gse->on_rq == true and the 2nd loop because the cfs is throttled whereas we have to update both load_avg with the old h_nr_running and increase h_nr_running in such case. The same sequence can happen during dequeue when se moves to parent before breaking in the 1st loop. Note that the update of load_avg will effectively happen only once in order to sync up to the throttled time. Next call for updating load_avg will stop early because the clock stays unchanged. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Fixes: 6d4d22468dae ("sched/fair: Reorder enqueue/dequeue_task_fair path") Link: https://lkml.kernel.org/r/20200306084208.12583-1-vincent.guittot@linaro.org
Diffstat (limited to 'kernel/sched/fair.c')
-rw-r--r--kernel/sched/fair.c17
1 files changed, 9 insertions, 8 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 54bd6280676e..1dea8554ead0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5460,16 +5460,16 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
- /* end evaluation on encountering a throttled cfs_rq */
- if (cfs_rq_throttled(cfs_rq))
- goto enqueue_throttle;
-
update_load_avg(cfs_rq, se, UPDATE_TG);
se_update_runnable(se);
update_cfs_group(se);
cfs_rq->h_nr_running++;
cfs_rq->idle_h_nr_running += idle_h_nr_running;
+
+ /* end evaluation on encountering a throttled cfs_rq */
+ if (cfs_rq_throttled(cfs_rq))
+ goto enqueue_throttle;
}
enqueue_throttle:
@@ -5558,16 +5558,17 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
- /* end evaluation on encountering a throttled cfs_rq */
- if (cfs_rq_throttled(cfs_rq))
- goto dequeue_throttle;
-
update_load_avg(cfs_rq, se, UPDATE_TG);
se_update_runnable(se);
update_cfs_group(se);
cfs_rq->h_nr_running--;
cfs_rq->idle_h_nr_running -= idle_h_nr_running;
+
+ /* end evaluation on encountering a throttled cfs_rq */
+ if (cfs_rq_throttled(cfs_rq))
+ goto dequeue_throttle;
+
}
dequeue_throttle: