Revert "sched/deadline: Remove cpu_active_mask from cpudl_find()"

This reverts commit 9659e1ee. The change leaves a possibility of
scheduling dl task on offline cpu. The original commit text suggests
that it should not be a problem since migrate_tasks() will take care of
it, but there can be delay between marking cpu as offline and
migrate_tasks() call since they are called on different hotplug
notifications-offline happens on CPUHP_TEARDOWN_CPU while
migrate_tasks() gets called on CPUHP_AP_SCHED_STARTING. And in
between this duration there is a chance the dl task can get scheduled on
this offline cpu and lead to BUG_ON. Hence revert the change.

Change-Id: I6f4ea10d2ce4e83e12d36b9b90b1b630ffe4fc74
[pujag@codeaurora.org: fix minor conflicts due to reorg of the code]
Signed-off-by: Puja Gupta <pujag@codeaurora.org>

kernel/sched/cpudeadline.c

@@ -124,7 +124,8 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
 	const struct sched_dl_entity *dl_se = &p->dl;
 
 	if (later_mask &&
-	    cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
+	    cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed) &&
+	    cpumask_and(later_mask, later_mask, cpu_active_mask)) {
 		return 1;
 	} else {
 		int best_cpu = cpudl_maximum(cp);
@@ -132,6 +133,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
 		WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
 
 		if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
+		    cpumask_test_cpu(best_cpu, cpu_active_mask) &&
 		    dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
 			if (later_mask)
 				cpumask_set_cpu(best_cpu, later_mask);