4 files changed, 37 insertions, 24 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 091e089063be..6fedf3a98581 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5738,15 +5738,10 @@ int sched_cpu_activate(unsigned int cpu)
 
 #ifdef CONFIG_SCHED_SMT
 	/*
-	 * The sched_smt_present static key needs to be evaluated on every
-	 * hotplug event because at boot time SMT might be disabled when
-	 * the number of booted CPUs is limited.
-	 *
-	 * If then later a sibling gets hotplugged, then the key would stay
-	 * off and SMT scheduling would never be functional.
+	 * When going up, increment the number of cores with SMT present.
 	 */
-	if (cpumask_weight(cpu_smt_mask(cpu)) > 1)
-		static_branch_enable_cpuslocked(&sched_smt_present);
+	if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
+		static_branch_inc_cpuslocked(&sched_smt_present);
 #endif
 	set_cpu_active(cpu, true);
 
@@ -5790,6 +5785,14 @@ int sched_cpu_deactivate(unsigned int cpu)
 	 */
 	synchronize_rcu_mult(call_rcu, call_rcu_sched);
 
+#ifdef CONFIG_SCHED_SMT
+	/*
+	 * When going down, decrement the number of cores with SMT present.
+	 */
+	if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
+		static_branch_dec_cpuslocked(&sched_smt_present);
+#endif
+
 	if (!sched_smp_initialized)
 		return 0;
 
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 3d7355d7c3e3..fe24de3fbc93 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -136,8 +136,18 @@
 
 static int psi_bug __read_mostly;
 
-bool psi_disabled __read_mostly;
-core_param(psi_disabled, psi_disabled, bool, 0644);
+DEFINE_STATIC_KEY_FALSE(psi_disabled);
+
+#ifdef CONFIG_PSI_DEFAULT_DISABLED
+bool psi_enable;
+#else
+bool psi_enable = true;
+#endif
+static int __init setup_psi(char *str)
+{
+	return kstrtobool(str, &psi_enable) == 0;
+}
+__setup("psi=", setup_psi);
 
 /* Running averages - we need to be higher-res than loadavg */
 #define PSI_FREQ	(2*HZ+1)	/* 2 sec intervals */
@@ -169,8 +179,10 @@ static void group_init(struct psi_group *group)
 
 void __init psi_init(void)
 {
-	if (psi_disabled)
+	if (!psi_enable) {
+		static_branch_enable(&psi_disabled);
 		return;
+	}
 
 	psi_period = jiffies_to_nsecs(PSI_FREQ);
 	group_init(&psi_system);
@@ -549,7 +561,7 @@ void psi_memstall_enter(unsigned long *flags)
 	struct rq_flags rf;
 	struct rq *rq;
 
-	if (psi_disabled)
+	if (static_branch_likely(&psi_disabled))
 		return;
 
 	*flags = current->flags & PF_MEMSTALL;
@@ -579,7 +591,7 @@ void psi_memstall_leave(unsigned long *flags)
 	struct rq_flags rf;
 	struct rq *rq;
 
-	if (psi_disabled)
+	if (static_branch_likely(&psi_disabled))
 		return;
 
 	if (*flags)
@@ -600,7 +612,7 @@ void psi_memstall_leave(unsigned long *flags)
 #ifdef CONFIG_CGROUPS
 int psi_cgroup_alloc(struct cgroup *cgroup)
 {
-	if (psi_disabled)
+	if (static_branch_likely(&psi_disabled))
 		return 0;
 
 	cgroup->psi.pcpu = alloc_percpu(struct psi_group_cpu);
@@ -612,7 +624,7 @@ int psi_cgroup_alloc(struct cgroup *cgroup)
 
 void psi_cgroup_free(struct cgroup *cgroup)
 {
-	if (psi_disabled)
+	if (static_branch_likely(&psi_disabled))
 		return;
 
 	cancel_delayed_work_sync(&cgroup->psi.clock_work);
@@ -637,7 +649,7 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to)
 	struct rq_flags rf;
 	struct rq *rq;
 
-	if (psi_disabled) {
+	if (static_branch_likely(&psi_disabled)) {
 		/*
 		 * Lame to do this here, but the scheduler cannot be locked
 		 * from the outside, so we move cgroups from inside sched/.
@@ -673,7 +685,7 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res)
 {
 	int full;
 
-	if (psi_disabled)
+	if (static_branch_likely(&psi_disabled))
 		return -EOPNOTSUPP;
 
 	update_stats(group);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 618577fc9aa8..4e524ab589c9 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -23,6 +23,7 @@
 #include <linux/sched/prio.h>
 #include <linux/sched/rt.h>
 #include <linux/sched/signal.h>
+#include <linux/sched/smt.h>
 #include <linux/sched/stat.h>
 #include <linux/sched/sysctl.h>
 #include <linux/sched/task.h>
@@ -936,9 +937,6 @@ static inline int cpu_of(struct rq *rq)
 
 
 #ifdef CONFIG_SCHED_SMT
-
-extern struct static_key_false sched_smt_present;
-
 extern void __update_idle_core(struct rq *rq);
 
 static inline void update_idle_core(struct rq *rq)
diff --git a/kernel/sched/stats.h b/kernel/sched/stats.h
index 4904c4677000..aa0de240fb41 100644
--- a/kernel/sched/stats.h
+++ b/kernel/sched/stats.h
@@ -66,7 +66,7 @@ static inline void psi_enqueue(struct task_struct *p, bool wakeup)
 {
 	int clear = 0, set = TSK_RUNNING;
 
-	if (psi_disabled)
+	if (static_branch_likely(&psi_disabled))
 		return;
 
 	if (!wakeup || p->sched_psi_wake_requeue) {
@@ -86,7 +86,7 @@ static inline void psi_dequeue(struct task_struct *p, bool sleep)
 {
 	int clear = TSK_RUNNING, set = 0;
 
-	if (psi_disabled)
+	if (static_branch_likely(&psi_disabled))
 		return;
 
 	if (!sleep) {
@@ -102,7 +102,7 @@ static inline void psi_dequeue(struct task_struct *p, bool sleep)
 
 static inline void psi_ttwu_dequeue(struct task_struct *p)
 {
-	if (psi_disabled)
+	if (static_branch_likely(&psi_disabled))
 		return;
 	/*
 	 * Is the task being migrated during a wakeup? Make sure to
@@ -128,7 +128,7 @@ static inline void psi_ttwu_dequeue(struct task_struct *p)
 
 static inline void psi_task_tick(struct rq *rq)
 {
-	if (psi_disabled)
+	if (static_branch_likely(&psi_disabled))
 		return;
 
 	if (unlikely(rq->curr->flags & PF_MEMSTALL))