Commit 3cb2d840 authored Mar 13, 2019 by Puja Gupta

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>

parent 47907c90

kernel/sched/cpudeadline.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -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);