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    Subject[PATCH v2 4/7] sched/deadline: reschedule if stop task slip in after pull operations
    Date
    pull_dl_task can drop (and re-acquire) rq->lock, this means a stop task
    can slip in, in which case we need to reschedule. This patch add the
    reschedule when the scenario occurs.

    Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
    ---
    kernel/sched/deadline.c | 16 +++++++++++++++-
    1 file changed, 15 insertions(+), 1 deletion(-)

    diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
    index e49b1e6..7d4c4fc 100644
    --- a/kernel/sched/deadline.c
    +++ b/kernel/sched/deadline.c
    @@ -1750,7 +1750,13 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
    if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
    return;

    - if (pull_dl_task(rq))
    + /*
    + * pull_dl_task() can drop (and re-acquire) rq->lock; this
    + * means a stop task can slip in, in which case we need to
    + * reschedule.
    + */
    + if (pull_dl_task(rq) ||
    + (rq->stop && task_on_rq_queued(rq->stop)))
    resched_curr(rq);
    }

    @@ -1797,6 +1803,14 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
    pull_dl_task(rq);

    /*
    + * pull_dl_task() can drop (and re-acquire) rq->lock; this
    + * means a stop task can slip in, in which case we need to
    + * reschedule.
    + */
    + if (rq->stop && task_on_rq_queued(rq->stop))
    + resched_curr(rq);
    +
    + /*
    * If we now have a earlier deadline task than p,
    * then reschedule, provided p is still on this
    * runqueue.
    --
    1.9.1


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