| From e7c7ffd0bc47695341c3aa84b2ae0ecb1381131c Mon Sep 17 00:00:00 2001 |
| From: Vincent Guittot <vincent.guittot@linaro.org> |
| Date: Fri, 6 Mar 2020 14:52:57 +0100 |
| Subject: [PATCH] sched/fair: Fix enqueue_task_fair warning |
| |
| commit fe61468b2cbc2b7ce5f8d3bf32ae5001d4c434e9 upstream. |
| |
| When a cfs rq is throttled, the latter and its child are removed from the |
| leaf list but their nr_running is not changed which includes staying higher |
| than 1. When a task is enqueued in this throttled branch, the cfs rqs must |
| be added back in order to ensure correct ordering in the list but this can |
| only happens if nr_running == 1. |
| When cfs bandwidth is used, we call unconditionnaly list_add_leaf_cfs_rq() |
| when enqueuing an entity to make sure that the complete branch will be |
| added. |
| |
| Similarly unthrottle_cfs_rq() can stop adding cfs in the list when a parent |
| is throttled. Iterate the remaining entity to ensure that the complete |
| branch will be added in the list. |
| |
| Reported-by: Christian Borntraeger <borntraeger@de.ibm.com> |
| Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> |
| Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> |
| Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> |
| Tested-by: Christian Borntraeger <borntraeger@de.ibm.com> |
| Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> |
| Cc: stable@vger.kernel.org |
| Cc: stable@vger.kernel.org #v5.1+ |
| Link: https://lkml.kernel.org/r/20200306135257.25044-1-vincent.guittot@linaro.org |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c |
| index 46198a9adf55..db8d7b097c79 100644 |
| --- a/kernel/sched/fair.c |
| +++ b/kernel/sched/fair.c |
| @@ -3909,6 +3909,7 @@ static inline void check_schedstat_required(void) |
| #endif |
| } |
| |
| +static inline bool cfs_bandwidth_used(void); |
| |
| /* |
| * MIGRATION |
| @@ -3987,10 +3988,16 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) |
| __enqueue_entity(cfs_rq, se); |
| se->on_rq = 1; |
| |
| - if (cfs_rq->nr_running == 1) { |
| + /* |
| + * When bandwidth control is enabled, cfs might have been removed |
| + * because of a parent been throttled but cfs->nr_running > 1. Try to |
| + * add it unconditionnally. |
| + */ |
| + if (cfs_rq->nr_running == 1 || cfs_bandwidth_used()) |
| list_add_leaf_cfs_rq(cfs_rq); |
| + |
| + if (cfs_rq->nr_running == 1) |
| check_enqueue_throttle(cfs_rq); |
| - } |
| } |
| |
| static void __clear_buddies_last(struct sched_entity *se) |
| @@ -4576,11 +4583,22 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) |
| break; |
| } |
| |
| - assert_list_leaf_cfs_rq(rq); |
| - |
| if (!se) |
| add_nr_running(rq, task_delta); |
| |
| + /* |
| + * The cfs_rq_throttled() breaks in the above iteration can result in |
| + * incomplete leaf list maintenance, resulting in triggering the |
| + * assertion below. |
| + */ |
| + for_each_sched_entity(se) { |
| + cfs_rq = cfs_rq_of(se); |
| + |
| + list_add_leaf_cfs_rq(cfs_rq); |
| + } |
| + |
| + assert_list_leaf_cfs_rq(rq); |
| + |
| /* Determine whether we need to wake up potentially idle CPU: */ |
| if (rq->curr == rq->idle && rq->cfs.nr_running) |
| resched_curr(rq); |
| -- |
| 2.7.4 |
| |