sched/deadline: Fix rq->dl.pushable_tasks bug in push_dl_task()

Do not call dequeue_pushable_dl_task() when failing to push an eligible
task, as it remains pushable, merely not at this particular moment.

Actually the patch is the same behavior as commit 311e800e16f6 ("sched,
rt: Fix rq->rt.pushable_tasks bug in push_rt_task()" in -rt side.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Kirill Tkhai <ktkhai@parallels.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1415258564-8573-1-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index bb1464baee84..9594c128ff17 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1328,6 +1328,7 @@ static int push_dl_task(struct rq *rq)
 {
         struct task_struct *next_task;
         struct rq *later_rq;
+        int ret = 0;
 
         if (!rq->dl.overloaded)
                 return 0;
@@ -1373,7 +1374,6 @@ retry:
                          * The task is still there. We don't try
                          * again, some other cpu will pull it when ready.
                          */
-                        dequeue_pushable_dl_task(rq, next_task);
                         goto out;
                 }
 
@@ -1389,6 +1389,7 @@ retry:
         deactivate_task(rq, next_task, 0);
         set_task_cpu(next_task, later_rq->cpu);
         activate_task(later_rq, next_task, 0);
+        ret = 1;
 
         resched_curr(later_rq);
 
@@ -1397,7 +1398,7 @@ retry:
 out:
         put_task_struct(next_task);
 
-        return 1;
+        return ret;
 }
 
 static void push_dl_tasks(struct rq *rq)