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-rw-r--r--kernel/sched/fair.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 525d69e5fb78..2d1ac6e2386d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5338,6 +5338,19 @@ static void task_move_group_fair(struct task_struct *p, int on_rq)
* to another cgroup's rq. This does somewhat interfere with the
* fair sleeper stuff for the first placement, but who cares.
*/
+ /*
+ * When !on_rq, vruntime of the task has usually NOT been normalized.
+ * But there are some cases where it has already been normalized:
+ *
+ * - Moving a forked child which is waiting for being woken up by
+ * wake_up_new_task().
+ *
+ * To prevent boost or penalty in the new cfs_rq caused by delta
+ * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
+ */
+ if (!on_rq && !p->se.sum_exec_runtime)
+ on_rq = 1;
+
if (!on_rq)
p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
set_task_rq(p, task_cpu(p));