In __synchronize_entity_decay(), if "decays" happens to be zero,
se->avg.decay_count will not be zeroed, holding the positive value
assigned when dequeued last time.
This is problematic in the following case:
If this runnable task is CFS-balanced to other CPUs soon afterwards,
migrate_task_rq_fair() will treat it as a blocked task due to its
non-zero decay_count, thereby adding its load to cfs_rq->removed_load
wrongly.
Thus, we must zero se->avg.decay_count in this case as well.
Signed-off-by: Xunlei Pang <pang.xun...@linaro.org>
---
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index df2cdf7..ea517cd 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2574,11 +2574,11 @@ static inline u64 __synchronize_entity_decay(struct
sched_entity *se)
u64 decays = atomic64_read(&cfs_rq->decay_counter);
decays -= se->avg.decay_count;
+ se->avg.decay_count = 0;
if (!decays)
return 0;
se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
- se->avg.decay_count = 0;
return decays;
}
--
1.9.1
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