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    Subject[tip:sched/core] sched: Don't update shares twice on on_rq parent
    Commit-ID:  9598c82dcacadc3b9daa8170613fd054c6124d30
    Gitweb: http://git.kernel.org/tip/9598c82dcacadc3b9daa8170613fd054c6124d30
    Author: Paul Turner <pjt@google.com>
    AuthorDate: Wed, 6 Jul 2011 22:30:37 -0700
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Thu, 21 Jul 2011 18:01:44 +0200

    sched: Don't update shares twice on on_rq parent

    In dequeue_task_fair() we bail on dequeue when we encounter a parenting entity
    with additional weight. However, we perform a double shares update on this
    entity as we continue the shares update traversal from this point, despite
    dequeue_entity() having already updated its queuing cfs_rq.
    Avoid this by starting from the parent when we resume.

    Signed-off-by: Paul Turner <pjt@google.com>
    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Link: http://lkml.kernel.org/r/20110707053059.797714697@google.com
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    kernel/sched_fair.c | 3 +++
    1 files changed, 3 insertions(+), 0 deletions(-)

    diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
    index f88720b..6cdff84 100644
    --- a/kernel/sched_fair.c
    +++ b/kernel/sched_fair.c
    @@ -1370,6 +1370,9 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
    */
    if (task_sleep && parent_entity(se))
    set_next_buddy(parent_entity(se));
    +
    + /* avoid re-evaluating load for this entity */
    + se = parent_entity(se);
    break;
    }
    flags |= DEQUEUE_SLEEP;

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