4 files changed, 32 insertions, 46 deletions

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index d769ec941fd3..067082e3fd41 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -4,6 +4,7 @@
 enum cpuhp_state {
         CPUHP_OFFLINE,
         CPUHP_CREATE_THREADS,
+        CPUHP_PERF_PREPARE,
         CPUHP_NOTIFY_PREPARE,
         CPUHP_BRINGUP_CPU,
         CPUHP_AP_IDLE_DEAD,
@@ -22,6 +23,7 @@ enum cpuhp_state {
         CPUHP_AP_ONLINE_IDLE,
         CPUHP_AP_SMPBOOT_THREADS,
         CPUHP_AP_X86_VDSO_VMA_ONLINE,
+        CPUHP_AP_PERF_ONLINE,
         CPUHP_AP_NOTIFY_ONLINE,
         CPUHP_AP_ONLINE_DYN,
         CPUHP_AP_ONLINE_DYN_END         = CPUHP_AP_ONLINE_DYN + 30,
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 1a827cecd62f..9abeb6948e70 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1354,4 +1354,13 @@ _name##_show(struct device *dev,					\
                                                                         \
 static struct device_attribute format_attr_##_name = __ATTR_RO(_name)
 
+/* Performance counter hotplug functions */
+#ifdef CONFIG_PERF_EVENTS
+int perf_event_init_cpu(unsigned int cpu);
+int perf_event_exit_cpu(unsigned int cpu);
+#else
+#define perf_event_init_cpu     NULL
+#define perf_event_exit_cpu     NULL
+#endif
+
 #endif /* _LINUX_PERF_EVENT_H */
diff --git a/kernel/cpu.c b/kernel/cpu.c
index fe71ce4e60f1..3705d9043c08 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1180,6 +1180,11 @@ static struct cpuhp_step cpuhp_bp_states[] = {
                 .teardown               = NULL,
                 .cant_stop              = true,
         },
+        [CPUHP_PERF_PREPARE] = {
+                .name = "perf prepare",
+                .startup = perf_event_init_cpu,
+                .teardown = perf_event_exit_cpu,
+        },
         /*
          * Preparatory and dead notifiers. Will be replaced once the notifiers
          * are converted to states.
@@ -1257,6 +1262,12 @@ static struct cpuhp_step cpuhp_ap_states[] = {
                 .startup                = smpboot_unpark_threads,
                 .teardown               = NULL,
         },
+        [CPUHP_AP_PERF_ONLINE] = {
+                .name = "perf online",
+                .startup = perf_event_init_cpu,
+                .teardown = perf_event_exit_cpu,
+        },
+
         /*
          * Online/down_prepare notifiers. Will be removed once the notifiers
          * are converted to states.
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 43d43a2d5811..f3ef1c29a7c9 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10255,7 +10255,7 @@ static void __init perf_event_init_all_cpus(void)
         }
 }
 
-static void perf_event_init_cpu(int cpu)
+int perf_event_init_cpu(unsigned int cpu)
 {
         struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);
 
@@ -10268,6 +10268,7 @@ static void perf_event_init_cpu(int cpu)
                 rcu_assign_pointer(swhash->swevent_hlist, hlist);
         }
         mutex_unlock(&swhash->hlist_mutex);
+        return 0;
 }
 
 #if defined CONFIG_HOTPLUG_CPU || defined CONFIG_KEXEC_CORE
@@ -10299,14 +10300,17 @@ static void perf_event_exit_cpu_context(int cpu)
         }
         srcu_read_unlock(&pmus_srcu, idx);
 }
+#else
+
+static void perf_event_exit_cpu_context(int cpu) { }
+
+#endif
 
-static void perf_event_exit_cpu(int cpu)
+int perf_event_exit_cpu(unsigned int cpu)
 {
         perf_event_exit_cpu_context(cpu);
+        return 0;
 }
-#else
-static inline void perf_event_exit_cpu(int cpu) { }
-#endif
 
 static int
 perf_reboot(struct notifier_block *notifier, unsigned long val, void *v)
@@ -10328,46 +10332,6 @@ static struct notifier_block perf_reboot_notifier = {
         .priority = INT_MIN,
 };
 
-static int
-perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
-{
-        unsigned int cpu = (long)hcpu;
-
-        switch (action & ~CPU_TASKS_FROZEN) {
-
-        case CPU_UP_PREPARE:
-                /*
-                 * This must be done before the CPU comes alive, because the
-                 * moment we can run tasks we can encounter (software) events.
-                 *
-                 * Specifically, someone can have inherited events on kthreadd
-                 * or a pre-existing worker thread that gets re-bound.
-                 */
-                perf_event_init_cpu(cpu);
-                break;
-
-        case CPU_DOWN_PREPARE:
-                /*
-                 * This must be done before the CPU dies because after that an
-                 * active event might want to IPI the CPU and that'll not work
-                 * so great for dead CPUs.
-                 *
-                 * XXX smp_call_function_single() return -ENXIO without a warn
-                 * so we could possibly deal with this.
-                 *
-                 * This is safe against new events arriving because
-                 * sys_perf_event_open() serializes against hotplug using
-                 * get_online_cpus().
-                 */
-                perf_event_exit_cpu(cpu);
-                break;
-        default:
-                break;
-        }
-
-        return NOTIFY_OK;
-}
-
 void __init perf_event_init(void)
 {
         int ret;
@@ -10380,7 +10344,7 @@ void __init perf_event_init(void)
         perf_pmu_register(&perf_cpu_clock, NULL, -1);
         perf_pmu_register(&perf_task_clock, NULL, -1);
         perf_tp_register();
-        perf_cpu_notifier(perf_cpu_notify);
+        perf_event_init_cpu(smp_processor_id());
         register_reboot_notifier(&perf_reboot_notifier);
 
         ret = init_hw_breakpoint();