Fix prefetched state of restarted tasks

src/core/task.c

@@ -740,6 +740,7 @@ static int _starpu_task_submit_head(struct starpu_task *task)
 		task->status = STARPU_TASK_INVALID;
 	else
 		STARPU_ASSERT(task->status == STARPU_TASK_INVALID);
+	task->prefetched = 0;
 
 	if (j->internal)
 	{