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    Subject[PATCH -v3 3/8] sched/deadline/rtmutex: Dont miss the dl_runtime/dl_period update
    From: Xunlei Pang <xlpang@redhat.com>

    Currently dl tasks will actually return at the very beginning
    of rt_mutex_adjust_prio_chain() in !detect_deadlock cases:

    if (waiter->prio == task->prio) {
    if (!detect_deadlock)
    goto out_unlock_pi; // out here
    else
    requeue = false;
    }

    As the deadline value of blocked deadline tasks(waiters) without
    changing their sched_class(thus prio doesn't change) never changes,
    this seems reasonable, but it actually misses the chance of updating
    rt_mutex_waiter's "dl_runtime(period)_copy" if a waiter updates its
    deadline parameters(dl_runtime, dl_period) or boosted waiter changes
    to !deadline class.

    Thus, force deadline task not out by adding the !dl_prio() condition.

    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Juri Lelli <juri.lelli@arm.com>
    Acked-by: Steven Rostedt <rostedt@goodmis.org>
    Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Xunlei Pang <xlpang@redhat.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Link: http://lkml.kernel.org/r/1460633827-345-7-git-send-email-xlpang@redhat.com
    ---
    kernel/locking/rtmutex.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/kernel/locking/rtmutex.c
    +++ b/kernel/locking/rtmutex.c
    @@ -488,7 +488,7 @@ static int rt_mutex_adjust_prio_chain(st
    * enabled we continue, but stop the requeueing in the chain
    * walk.
    */
    - if (waiter->prio == task->prio) {
    + if (waiter->prio == task->prio && !dl_task(task)) {
    if (!detect_deadlock)
    goto out_unlock_pi;
    else

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