x86/mce/therm_throt: 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: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: rt@linuxtronix.de
Cc: Borislav Petkov <bp@alien8.de>
Cc: linux-edac@vger.kernel.org
Link: http://lkml.kernel.org/r/20161117183541.8588-2-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/cpu/mcheck/therm_throt.c

@@ -271,58 +271,29 @@ static void thermal_throttle_remove_dev(struct device *dev)
 }
 
 /* Get notified when a cpu comes on/off. Be hotplug friendly. */
-static int
-thermal_throttle_cpu_callback(struct notifier_block *nfb,
-			      unsigned long action,
-			      void *hcpu)
+static int thermal_throttle_prepare(unsigned int cpu)
 {
-	unsigned int cpu = (unsigned long)hcpu;
-	struct device *dev;
-	int err = 0;
-
-	dev = get_cpu_device(cpu);
-
-	switch (action) {
-	case CPU_UP_PREPARE:
-	case CPU_UP_PREPARE_FROZEN:
-		err = thermal_throttle_add_dev(dev, cpu);
-		WARN_ON(err);
-		break;
-	case CPU_UP_CANCELED:
-	case CPU_UP_CANCELED_FROZEN:
-	case CPU_DEAD:
-	case CPU_DEAD_FROZEN:
-		thermal_throttle_remove_dev(dev);
-		break;
-	}
-	return notifier_from_errno(err);
+	struct device *dev = get_cpu_device(cpu);
+
+	return thermal_throttle_add_dev(dev, cpu);
 }
 
-static struct notifier_block thermal_throttle_cpu_notifier =
+static int thermal_throttle_dead(unsigned int cpu)
 {
-	.notifier_call = thermal_throttle_cpu_callback,
-};
+	struct device *dev = get_cpu_device(cpu);
+
+	thermal_throttle_remove_dev(dev);
+	return 0;
+}
 
 static __init int thermal_throttle_init_device(void)
 {
-	unsigned int cpu = 0;
-	int err;
-
 	if (!atomic_read(&therm_throt_en))
 		return 0;
 
-	cpu_notifier_register_begin();
-
-	/* connect live CPUs to sysfs */
-	for_each_online_cpu(cpu) {
-		err = thermal_throttle_add_dev(get_cpu_device(cpu), cpu);
-		WARN_ON(err);
-	}
-
-	__register_hotcpu_notifier(&thermal_throttle_cpu_notifier);
-	cpu_notifier_register_done();
-
-	return 0;
+	return cpuhp_setup_state(CPUHP_X86_THERM_PREPARE, "x86/therm:prepare",
+				 thermal_throttle_prepare,
+				 thermal_throttle_dead);
 }
 device_initcall(thermal_throttle_init_device);
 

include/linux/cpuhotplug.h

@@ -59,6 +59,7 @@ enum cpuhp_state {
 	CPUHP_BLK_MQ_PREPARE,
 	CPUHP_NET_FLOW_PREPARE,
 	CPUHP_TOPOLOGY_PREPARE,
+	CPUHP_X86_THERM_PREPARE,
 	CPUHP_TIMERS_DEAD,
 	CPUHP_NOTF_ERR_INJ_PREPARE,
 	CPUHP_MIPS_SOC_PREPARE,