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Subject[PATCH 1/1] sched/fair: Fix the wrong sched_stat_wait time
Date
From: jun qian <qianjun.kernel@gmail.com>

When the sched_schedstat changes from 0 to 1, some sched se maybe
already in the runqueue, the se->statistics.wait_start will be 0.
So it will let the (rq_of(cfs_rq)) - se->statistics.wait_start)
wrong. We need to avoid this scenario.

Signed-off-by: jun qian <qianjun.kernel@gmail.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
kernel/sched/fair.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 658aa7a..dd7c3bb 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -908,6 +908,14 @@ static void update_curr_fair(struct rq *rq)
if (!schedstat_enabled())
return;

+ /*
+ * When the sched_schedstat changes from 0 to 1, some sched se maybe
+ * already in the runqueue, the se->statistics.wait_start will be 0.
+ * So it will let the delta wrong. We need to avoid this scenario.
+ */
+ if (unlikely(!schedstat_val(se->statistics.wait_start)))
+ return;
+
delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);

if (entity_is_task(se)) {
--
1.8.3.1
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