1 files changed, 49 insertions, 24 deletions

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 72c1f72463c7..615411a0a881 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2551,6 +2551,25 @@ static int find_later_rq(struct task_struct *task)
 	return -1;
 }
 
+static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
+{
+	struct task_struct *p;
+
+	if (!has_pushable_dl_tasks(rq))
+		return NULL;
+
+	p = __node_2_pdl(rb_first_cached(&rq->dl.pushable_dl_tasks_root));
+
+	WARN_ON_ONCE(rq->cpu != task_cpu(p));
+	WARN_ON_ONCE(task_current(rq, p));
+	WARN_ON_ONCE(p->nr_cpus_allowed <= 1);
+
+	WARN_ON_ONCE(!task_on_rq_queued(p));
+	WARN_ON_ONCE(!dl_task(p));
+
+	return p;
+}
+
 /* Locks the rq it finds */
 static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
 {
@@ -2578,12 +2597,37 @@ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
 
 		/* Retry if something changed. */
 		if (double_lock_balance(rq, later_rq)) {
-			if (unlikely(task_rq(task) != rq ||
+			/*
+			 * double_lock_balance had to release rq->lock, in the
+			 * meantime, task may no longer be fit to be migrated.
+			 * Check the following to ensure that the task is
+			 * still suitable for migration:
+			 * 1. It is possible the task was scheduled,
+			 *    migrate_disabled was set and then got preempted,
+			 *    so we must check the task migration disable
+			 *    flag.
+			 * 2. The CPU picked is in the task's affinity.
+			 * 3. For throttled task (dl_task_offline_migration),
+			 *    check the following:
+			 *    - the task is not on the rq anymore (it was
+			 *      migrated)
+			 *    - the task is not on CPU anymore
+			 *    - the task is still a dl task
+			 *    - the task is not queued on the rq anymore
+			 * 4. For the non-throttled task (push_dl_task), the
+			 *    check to ensure that this task is still at the
+			 *    head of the pushable tasks list is enough.
+			 */
+			if (unlikely(is_migration_disabled(task) ||
 				     !cpumask_test_cpu(later_rq->cpu, &task->cpus_mask) ||
-				     task_on_cpu(rq, task) ||
-				     !dl_task(task) ||
-				     is_migration_disabled(task) ||
-				     !task_on_rq_queued(task))) {
+				     (task->dl.dl_throttled &&
+				      (task_rq(task) != rq ||
+				       task_on_cpu(rq, task) ||
+				       !dl_task(task) ||
+				       !task_on_rq_queued(task))) ||
+				     (!task->dl.dl_throttled &&
+				      task != pick_next_pushable_dl_task(rq)))) {
+
 				double_unlock_balance(rq, later_rq);
 				later_rq = NULL;
 				break;
@@ -2606,25 +2650,6 @@ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
 	return later_rq;
 }
 
-static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
-{
-	struct task_struct *p;
-
-	if (!has_pushable_dl_tasks(rq))
-		return NULL;
-
-	p = __node_2_pdl(rb_first_cached(&rq->dl.pushable_dl_tasks_root));
-
-	WARN_ON_ONCE(rq->cpu != task_cpu(p));
-	WARN_ON_ONCE(task_current(rq, p));
-	WARN_ON_ONCE(p->nr_cpus_allowed <= 1);
-
-	WARN_ON_ONCE(!task_on_rq_queued(p));
-	WARN_ON_ONCE(!dl_task(p));
-
-	return p;
-}
-
 /*
  * See if the non running -deadline tasks on this rq
  * can be sent to some other CPU where they can preempt