metag/perf: Convert 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: Richard Cochran <rcochran@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-metag@vger.kernel.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153336.717395164@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/metag/kernel/perf/perf_event.c

@@ -806,25 +806,16 @@ static struct metag_pmu _metag_pmu = {
 };
 
 /* PMU CPU hotplug notifier */
-static int metag_pmu_cpu_notify(struct notifier_block *b, unsigned long action,
-				void *hcpu)
+static int metag_pmu_starting_cpu(unsigned int cpu)
 {
-	unsigned int cpu = (unsigned int)hcpu;
 	struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
 
-	if ((action & ~CPU_TASKS_FROZEN) != CPU_STARTING)
-		return NOTIFY_DONE;
-
 	memset(cpuc, 0, sizeof(struct cpu_hw_events));
 	raw_spin_lock_init(&cpuc->pmu_lock);
 
-	return NOTIFY_OK;
+	return 0;
 }
 
-static struct notifier_block metag_pmu_notifier = {
-	.notifier_call = metag_pmu_cpu_notify,
-};
-
 /* PMU Initialisation */
 static int __init init_hw_perf_events(void)
 {
@@ -876,16 +867,13 @@ static int __init init_hw_perf_events(void)
 	metag_out32(0, PERF_COUNT(0));
 	metag_out32(0, PERF_COUNT(1));
 
-	for_each_possible_cpu(cpu) {
-		struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
+	cpuhp_setup_state(CPUHP_AP_PERF_METAG_STARTING,
+			  "AP_PERF_METAG_STARTING", metag_pmu_starting_cpu,
+			  NULL);
 
-		memset(cpuc, 0, sizeof(struct cpu_hw_events));
-		raw_spin_lock_init(&cpuc->pmu_lock);
-	}
-
-	register_cpu_notifier(&metag_pmu_notifier);
 	ret = perf_pmu_register(&pmu, metag_pmu->name, PERF_TYPE_RAW);
-out:
+	if (ret)
+		cpuhp_remove_state_nocalls(CPUHP_AP_PERF_METAG_STARTING);
 	return ret;
 }
 early_initcall(init_hw_perf_events);

include/linux/cpuhotplug.h

@@ -34,6 +34,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_X86_CQM_STARTING,
 	CPUHP_AP_PERF_X86_CSTATE_STARTING,
 	CPUHP_AP_PERF_XTENSA_STARTING,
+	CPUHP_AP_PERF_METAG_STARTING,
 	CPUHP_AP_ARM_VFP_STARTING,
 	CPUHP_AP_PERF_ARM_STARTING,
 	CPUHP_AP_ARM_ARCH_TIMER_STARTING,