s390/mm/pfault: Convert to hotplug state machine

Install the callbacks via the state machine.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-s390@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: rt@linutronix.de
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Link: http://lkml.kernel.org/r/20160906170457.32393-18-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/s390/mm/fault.c

@@ -740,28 +740,21 @@ static void pfault_interrupt(struct ext_code ext_code,
 	put_task_struct(tsk);
 }
 
-static int pfault_cpu_notify(struct notifier_block *self, unsigned long action,
-			     void *hcpu)
+static int pfault_cpu_dead(unsigned int cpu)
 {
 	struct thread_struct *thread, *next;
 	struct task_struct *tsk;
 
-	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_DEAD:
-		spin_lock_irq(&pfault_lock);
-		list_for_each_entry_safe(thread, next, &pfault_list, list) {
-			thread->pfault_wait = 0;
-			list_del(&thread->list);
-			tsk = container_of(thread, struct task_struct, thread);
-			wake_up_process(tsk);
-			put_task_struct(tsk);
-		}
-		spin_unlock_irq(&pfault_lock);
-		break;
-	default:
-		break;
+	spin_lock_irq(&pfault_lock);
+	list_for_each_entry_safe(thread, next, &pfault_list, list) {
+		thread->pfault_wait = 0;
+		list_del(&thread->list);
+		tsk = container_of(thread, struct task_struct, thread);
+		wake_up_process(tsk);
+		put_task_struct(tsk);
 	}
-	return NOTIFY_OK;
+	spin_unlock_irq(&pfault_lock);
+	return 0;
 }
 
 static int __init pfault_irq_init(void)
@@ -775,7 +768,8 @@ static int __init pfault_irq_init(void)
 	if (rc)
 		goto out_pfault;
 	irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL);
-	hotcpu_notifier(pfault_cpu_notify, 0);
+	cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead",
+				  NULL, pfault_cpu_dead);
 	return 0;
 
 out_pfault:

include/linux/cpuhotplug.h

@@ -26,6 +26,7 @@ enum cpuhp_state {
 	CPUHP_BLOCK_SOFTIRQ_DEAD,
 	CPUHP_VIRT_SCSI_DEAD,
 	CPUHP_ACPI_CPUDRV_DEAD,
+	CPUHP_S390_PFAULT_DEAD,
 	CPUHP_WORKQUEUE_PREP,
 	CPUHP_POWER_NUMA_PREPARE,
 	CPUHP_HRTIMERS_PREPARE,