diff options
author | Vincent Guittot <vincent.guittot@linaro.org> | 2020-03-06 14:52:57 +0100 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-04-17 10:50:11 +0200 |
commit | 524089fa70ef10ba972c77818a7d145610598162 (patch) | |
tree | 83387286d510df1533487a46045271c542d03d31 /kernel/sched | |
parent | 8b6f8619fc96df797644c6dfe2fb8654e4c472f5 (diff) |
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r-- | kernel/sched/fair.c | 26 |
1 files changed, 22 insertions, 4 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index f32ce3a359fa..eeaf34d65742 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3927,6 +3927,7 @@ static inline void check_schedstat_required(void) #endif } +static inline bool cfs_bandwidth_used(void); /* * MIGRATION @@ -4005,10 +4006,16 @@ 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) @@ -4589,11 +4596,22 @@ 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); |