perf/x86/intel/cstate: Convert Intel CSTATE to hotplug state machine

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: kbuild test robot <fengguang.wu@intel.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153334.184061086@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/events/intel/cstate.c

@@ -365,7 +365,7 @@ static int cstate_pmu_event_add(struct perf_event *event, int mode)
  * Check if exiting cpu is the designated reader. If so migrate the
  * events when there is a valid target available
  */
-static void cstate_cpu_exit(int cpu)
+static int cstate_cpu_exit(unsigned int cpu)
 {
 	unsigned int target;
 
@@ -390,9 +390,10 @@ static void cstate_cpu_exit(int cpu)
 			perf_pmu_migrate_context(&cstate_pkg_pmu, cpu, target);
 		}
 	}
+	return 0;
 }
 
-static void cstate_cpu_init(int cpu)
+static int cstate_cpu_init(unsigned int cpu)
 {
 	unsigned int target;
 
@@ -414,31 +415,10 @@ static void cstate_cpu_init(int cpu)
 				 topology_core_cpumask(cpu));
 	if (has_cstate_pkg && target >= nr_cpu_ids)
 		cpumask_set_cpu(cpu, &cstate_pkg_cpu_mask);
+
+	return 0;
 }
 
-static int cstate_cpu_notifier(struct notifier_block *self,
-			       unsigned long action, void *hcpu)
-{
-	unsigned int cpu = (long)hcpu;
-
-	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_STARTING:
-		cstate_cpu_init(cpu);
-		break;
-	case CPU_DOWN_PREPARE:
-		cstate_cpu_exit(cpu);
-		break;
-	default:
-		break;
-	}
-	return NOTIFY_OK;
-}
-
-static struct notifier_block cstate_cpu_nb = {
-	.notifier_call	= cstate_cpu_notifier,
-	.priority       = CPU_PRI_PERF + 1,
-};
-
 static struct pmu cstate_core_pmu = {
 	.attr_groups	= core_attr_groups,
 	.name		= "cstate_core",
@@ -599,18 +579,20 @@ static inline void cstate_cleanup(void)
 
 static int __init cstate_init(void)
 {
-	int cpu, err;
+	int err;
 
-	cpu_notifier_register_begin();
-	for_each_online_cpu(cpu)
-		cstate_cpu_init(cpu);
+	cpuhp_setup_state(CPUHP_AP_PERF_X86_CSTATE_STARTING,
+			  "AP_PERF_X86_CSTATE_STARTING", cstate_cpu_init,
+			  NULL);
+	cpuhp_setup_state(CPUHP_AP_PERF_X86_CSTATE_ONLINE,
+			  "AP_PERF_X86_CSTATE_ONLINE", NULL, cstate_cpu_exit);
 
 	if (has_cstate_core) {
 		err = perf_pmu_register(&cstate_core_pmu, cstate_core_pmu.name, -1);
 		if (err) {
 			has_cstate_core = false;
 			pr_info("Failed to register cstate core pmu\n");
-			goto out;
+			return err;
 		}
 	}
 
@@ -620,12 +602,10 @@ static int __init cstate_init(void)
 			has_cstate_pkg = false;
 			pr_info("Failed to register cstate pkg pmu\n");
 			cstate_cleanup();
-			goto out;
+			return err;
 		}
 	}
-	__register_cpu_notifier(&cstate_cpu_nb);
-out:
-	cpu_notifier_register_done();
+
 	return err;
 }
 
@@ -651,9 +631,8 @@ module_init(cstate_pmu_init);
 
 static void __exit cstate_pmu_exit(void)
 {
-	cpu_notifier_register_begin();
-	__unregister_cpu_notifier(&cstate_cpu_nb);
+	cpuhp_remove_state_nocalls(CPUHP_AP_PERF_X86_CSTATE_ONLINE);
+	cpuhp_remove_state_nocalls(CPUHP_AP_PERF_X86_CSTATE_STARTING);
 	cstate_cleanup();
-	cpu_notifier_register_done();
 }
 module_exit(cstate_pmu_exit);

include/linux/cpuhotplug.h

@@ -26,6 +26,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_X86_STARTING,
 	CPUHP_AP_PERF_X86_AMD_IBS_STARTING,
 	CPUHP_AP_PERF_X86_CQM_STARTING,
+	CPUHP_AP_PERF_X86_CSTATE_STARTING,
 	CPUHP_AP_NOTIFY_STARTING,
 	CPUHP_AP_ONLINE,
 	CPUHP_TEARDOWN_CPU,
@@ -38,6 +39,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_X86_AMD_UNCORE_ONLINE,
 	CPUHP_AP_PERF_X86_RAPL_ONLINE,
 	CPUHP_AP_PERF_X86_CQM_ONLINE,
+	CPUHP_AP_PERF_X86_CSTATE_ONLINE,
 	CPUHP_AP_NOTIFY_ONLINE,
 	CPUHP_AP_ONLINE_DYN,
 	CPUHP_AP_ONLINE_DYN_END		= CPUHP_AP_ONLINE_DYN + 30,