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    Subject[PATCH v2] sched: fix first task of a task group is attached twice
    Date
    The cfs_rq->avg.last_update_time is initialize to 0 with the main effect
    that the 1st sched_entity that will be attached, will keep its
    last_update_time set to 0 and will attached once again during the
    enqueue.
    Initialize cfs_rq->avg.last_update_time to 1 instead.

    Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
    ---

    v2:
    - rq_clock_task(rq_of(cfs_rq)) can't be used because lock is not held

    kernel/sched/fair.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
    index 218f8e8..3724656 100644
    --- a/kernel/sched/fair.c
    +++ b/kernel/sched/fair.c
    @@ -8586,6 +8586,14 @@ void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
    se->depth = parent->depth + 1;
    }

    + /*
    + * Set last_update_time to something different from 0 to make
    + * sure the 1st sched_entity will not be attached twice: once
    + * when attaching the task to the group and one more time when
    + * enqueueing the task.
    + */
    + tg->cfs_rq[cpu]->avg.last_update_time = 1;
    +
    se->my_q = cfs_rq;
    /* guarantee group entities always have weight */
    update_load_set(&se->load, NICE_0_LOAD);
    --
    1.9.1
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