xtensa/perf: Convert the hotplug notifier to state machine callbacks

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@kernel.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-xtensa@linux-xtensa.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153334.852575891@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/xtensa/kernel/perf_event.c

@@ -404,7 +404,7 @@ static struct pmu xtensa_pmu = {
 	.read = xtensa_pmu_read,
 };
 
-static void xtensa_pmu_setup(void)
+static int xtensa_pmu_setup(int cpu)
 {
 	unsigned i;
 
@@ -413,29 +413,21 @@ static void xtensa_pmu_setup(void)
 		set_er(0, XTENSA_PMU_PMCTRL(i));
 		set_er(get_er(XTENSA_PMU_PMSTAT(i)), XTENSA_PMU_PMSTAT(i));
 	}
-}
-
-static int xtensa_pmu_notifier(struct notifier_block *self,
-			       unsigned long action, void *data)
-{
-	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_STARTING:
-		xtensa_pmu_setup();
-		break;
-
-	default:
-		break;
-	}
-
-	return NOTIFY_OK;
+	return 0;
 }
 
 static int __init xtensa_pmu_init(void)
 {
 	int ret;
 	int irq = irq_create_mapping(NULL, XCHAL_PROFILING_INTERRUPT);
 
-	perf_cpu_notifier(xtensa_pmu_notifier);
+	ret = cpuhp_setup_state(CPUHP_AP_PERF_XTENSA_STARTING,
+				"AP_PERF_XTENSA_STARTING", xtensa_pmu_setup,
+				NULL);
+	if (ret) {
+		pr_err("xtensa_pmu: failed to register CPU-hotplug.\n");
+		return ret;
+	}
 #if XTENSA_FAKE_NMI
 	enable_irq(irq);
 #else

include/linux/cpuhotplug.h

@@ -30,6 +30,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_X86_AMD_IBS_STARTING,
 	CPUHP_AP_PERF_X86_CQM_STARTING,
 	CPUHP_AP_PERF_X86_CSTATE_STARTING,
+	CPUHP_AP_PERF_XTENSA_STARTING,
 	CPUHP_AP_NOTIFY_STARTING,
 	CPUHP_AP_ONLINE,
 	CPUHP_TEARDOWN_CPU,