sched: fix new task startup crash

Child task may be added on a different cpu that the one on which parent
is running. In which case, task_new_fair() should check whether the new
born task's parent entity should be added as well on the cfs_rq.

Patch below fixes the problem in task_new_fair.

This could fix the put_prev_task_fair() crashes reported.

Reported-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Reported-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 2 insertions, 6 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 975436435b42..0ec9521a8e70 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1712,7 +1712,7 @@ void fastcall wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
 
         p->prio = effective_prio(p);
 
-        if (!p->sched_class->task_new || !current->se.on_rq || !rq->cfs.curr) {
+        if (!p->sched_class->task_new || !current->se.on_rq) {
                 activate_task(rq, p, 0);
         } else {
                 /*
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index a17b785d7000..166ed6db600b 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1031,12 +1031,8 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
                 swap(curr->vruntime, se->vruntime);
         }
 
-        update_stats_enqueue(cfs_rq, se);
-        check_spread(cfs_rq, se);
-        check_spread(cfs_rq, curr);
-        __enqueue_entity(cfs_rq, se);
-        account_entity_enqueue(cfs_rq, se);
         se->peer_preempt = 0;
+        enqueue_task_fair(rq, p, 0);
         resched_task(rq->curr);
 }