sched: Don't update shares twice on on_rq parent
Paul Turner [Thu, 7 Jul 2011 05:30:37 +0000 (22:30 -0700)]
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

index f88720b..6cdff84 100644 (file)
@@ -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;