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| author | kuyo chang <kuyo.chang@mediatek.com> | 2022-04-14 12:02:20 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-04-27 15:38:58 +0300 |
| commit | b1b929468229d286b6cd7b09673ef2556d5332bb (patch) | |
| tree | 6608474b0a6812b0042b5512b3224bf50d7d6f5c /kernel | |
| parent | 914473a0708874c69895f5f809b686f1797169a9 (diff) | |
| download | linux-b1b929468229d286b6cd7b09673ef2556d5332bb.tar.xz | |
sched/pelt: Fix attach_entity_load_avg() corner case
[ Upstream commit 40f5aa4c5eaebfeaca4566217cb9c468e28ed682 ]
The warning in cfs_rq_is_decayed() triggered:
SCHED_WARN_ON(cfs_rq->avg.load_avg ||
cfs_rq->avg.util_avg ||
cfs_rq->avg.runnable_avg)
There exists a corner case in attach_entity_load_avg() which will
cause load_sum to be zero while load_avg will not be.
Consider se_weight is 88761 as per the sched_prio_to_weight[] table.
Further assume the get_pelt_divider() is 47742, this gives:
se->avg.load_avg is 1.
However, calculating load_sum:
se->avg.load_sum = div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
se->avg.load_sum = 1*47742/88761 = 0.
Then enqueue_load_avg() adds this to the cfs_rq totals:
cfs_rq->avg.load_avg += se->avg.load_avg;
cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
Resulting in load_avg being 1 with load_sum is 0, which will trigger
the WARN.
Fixes: f207934fb79d ("sched/fair: Align PELT windows between cfs_rq and its se")
Signed-off-by: kuyo chang <kuyo.chang@mediatek.com>
[peterz: massage changelog]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20220414090229.342-1-kuyo.chang@mediatek.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/fair.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 02766f3fe206..9a4fa22a69ed 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3794,11 +3794,11 @@ static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s se->avg.runnable_sum = se->avg.runnable_avg * divider; - se->avg.load_sum = divider; - if (se_weight(se)) { - se->avg.load_sum = - div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se)); - } + se->avg.load_sum = se->avg.load_avg * divider; + if (se_weight(se) < se->avg.load_sum) + se->avg.load_sum = div_u64(se->avg.load_sum, se_weight(se)); + else + se->avg.load_sum = 1; enqueue_load_avg(cfs_rq, se); cfs_rq->avg.util_avg += se->avg.util_avg; |