1 files changed, 23 insertions, 19 deletions

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index cc25a3cff41f..1652f2bb54b7 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -148,6 +148,7 @@
 static int psi_bug __read_mostly;
 
 DEFINE_STATIC_KEY_FALSE(psi_disabled);
+DEFINE_STATIC_KEY_TRUE(psi_cgroups_enabled);
 
 #ifdef CONFIG_PSI_DEFAULT_DISABLED
 static bool psi_enable;
@@ -182,6 +183,8 @@ struct psi_group psi_system = {
 
 static void psi_avgs_work(struct work_struct *work);
 
+static void poll_timer_fn(struct timer_list *t);
+
 static void group_init(struct psi_group *group)
 {
 	int cpu;
@@ -201,6 +204,8 @@ static void group_init(struct psi_group *group)
 	memset(group->polling_total, 0, sizeof(group->polling_total));
 	group->polling_next_update = ULLONG_MAX;
 	group->polling_until = 0;
+	init_waitqueue_head(&group->poll_wait);
+	timer_setup(&group->poll_timer, poll_timer_fn, 0);
 	rcu_assign_pointer(group->poll_task, NULL);
 }
 
@@ -211,6 +216,9 @@ void __init psi_init(void)
 		return;
 	}
 
+	if (!cgroup_psi_enabled())
+		static_branch_disable(&psi_cgroups_enabled);
+
 	psi_period = jiffies_to_nsecs(PSI_FREQ);
 	group_init(&psi_system);
 }
@@ -744,23 +752,23 @@ static void psi_group_change(struct psi_group *group, int cpu,
 
 static struct psi_group *iterate_groups(struct task_struct *task, void **iter)
 {
+	if (*iter == &psi_system)
+		return NULL;
+
 #ifdef CONFIG_CGROUPS
-	struct cgroup *cgroup = NULL;
+	if (static_branch_likely(&psi_cgroups_enabled)) {
+		struct cgroup *cgroup = NULL;
 
-	if (!*iter)
-		cgroup = task->cgroups->dfl_cgrp;
-	else if (*iter == &psi_system)
-		return NULL;
-	else
-		cgroup = cgroup_parent(*iter);
+		if (!*iter)
+			cgroup = task->cgroups->dfl_cgrp;
+		else
+			cgroup = cgroup_parent(*iter);
 
-	if (cgroup && cgroup_parent(cgroup)) {
-		*iter = cgroup;
-		return cgroup_psi(cgroup);
+		if (cgroup && cgroup_parent(cgroup)) {
+			*iter = cgroup;
+			return cgroup_psi(cgroup);
+		}
 	}
-#else
-	if (*iter)
-		return NULL;
 #endif
 	*iter = &psi_system;
 	return &psi_system;
@@ -1157,9 +1165,7 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group,
 			return ERR_CAST(task);
 		}
 		atomic_set(&group->poll_wakeup, 0);
-		init_waitqueue_head(&group->poll_wait);
 		wake_up_process(task);
-		timer_setup(&group->poll_timer, poll_timer_fn, 0);
 		rcu_assign_pointer(group->poll_task, task);
 	}
 
@@ -1211,6 +1217,7 @@ static void psi_trigger_destroy(struct kref *ref)
 					group->poll_task,
 					lockdep_is_held(&group->trigger_lock));
 			rcu_assign_pointer(group->poll_task, NULL);
+			del_timer(&group->poll_timer);
 		}
 	}
 
@@ -1223,17 +1230,14 @@ static void psi_trigger_destroy(struct kref *ref)
 	 */
 	synchronize_rcu();
 	/*
-	 * Destroy the kworker after releasing trigger_lock to prevent a
+	 * Stop kthread 'psimon' after releasing trigger_lock to prevent a
 	 * deadlock while waiting for psi_poll_work to acquire trigger_lock
 	 */
 	if (task_to_destroy) {
 		/*
 		 * After the RCU grace period has expired, the worker
 		 * can no longer be found through group->poll_task.
-		 * But it might have been already scheduled before
-		 * that - deschedule it cleanly before destroying it.
 		 */
-		del_timer_sync(&group->poll_timer);
 		kthread_stop(task_to_destroy);
 	}
 	kfree(t);