powerpc/mmu nohash: Convert to hotplug state machine

Install the callbacks via the state machine.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: rt@linutronix.de
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/20160818125731.27256-17-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/powerpc/mm/mmu_context_nohash.c

@@ -369,44 +369,34 @@ void destroy_context(struct mm_struct *mm)
 }
 
 #ifdef CONFIG_SMP
-
-static int mmu_context_cpu_notify(struct notifier_block *self,
-				  unsigned long action, void *hcpu)
+static int mmu_ctx_cpu_prepare(unsigned int cpu)
 {
-	unsigned int cpu = (unsigned int)(long)hcpu;
-
 	/* We don't touch CPU 0 map, it's allocated at aboot and kept
 	 * around forever
 	 */
 	if (cpu == boot_cpuid)
-		return NOTIFY_OK;
-
-	switch (action) {
-	case CPU_UP_PREPARE:
-	case CPU_UP_PREPARE_FROZEN:
-		pr_devel("MMU: Allocating stale context map for CPU %d\n", cpu);
-		stale_map[cpu] = kzalloc(CTX_MAP_SIZE, GFP_KERNEL);
-		break;
-#ifdef CONFIG_HOTPLUG_CPU
-	case CPU_UP_CANCELED:
-	case CPU_UP_CANCELED_FROZEN:
-	case CPU_DEAD:
-	case CPU_DEAD_FROZEN:
-		pr_devel("MMU: Freeing stale context map for CPU %d\n", cpu);
-		kfree(stale_map[cpu]);
-		stale_map[cpu] = NULL;
-
-		/* We also clear the cpu_vm_mask bits of CPUs going away */
-		clear_tasks_mm_cpumask(cpu);
-	break;
-#endif /* CONFIG_HOTPLUG_CPU */
-	}
-	return NOTIFY_OK;
+		return 0;
+
+	pr_devel("MMU: Allocating stale context map for CPU %d\n", cpu);
+	stale_map[cpu] = kzalloc(CTX_MAP_SIZE, GFP_KERNEL);
+	return 0;
 }
 
-static struct notifier_block mmu_context_cpu_nb = {
-	.notifier_call	= mmu_context_cpu_notify,
-};
+static int mmu_ctx_cpu_dead(unsigned int cpu)
+{
+#ifdef CONFIG_HOTPLUG_CPU
+	if (cpu == boot_cpuid)
+		return 0;
+
+	pr_devel("MMU: Freeing stale context map for CPU %d\n", cpu);
+	kfree(stale_map[cpu]);
+	stale_map[cpu] = NULL;
+
+	/* We also clear the cpu_vm_mask bits of CPUs going away */
+	clear_tasks_mm_cpumask(cpu);
+#endif
+	return 0;
+}
 
 #endif /* CONFIG_SMP */
 
@@ -469,7 +459,9 @@ void __init mmu_context_init(void)
 #else
 	stale_map[boot_cpuid] = memblock_virt_alloc(CTX_MAP_SIZE, 0);
 
-	register_cpu_notifier(&mmu_context_cpu_nb);
+	cpuhp_setup_state_nocalls(CPUHP_POWERPC_MMU_CTX_PREPARE,
+				  "powerpc/mmu/ctx:prepare",
+				  mmu_ctx_cpu_prepare, mmu_ctx_cpu_dead);
 #endif
 
 	printk(KERN_INFO

include/linux/cpuhotplug.h

@@ -32,6 +32,7 @@ enum cpuhp_state {
 	CPUHP_RCUTREE_PREP,
 	CPUHP_CPUIDLE_COUPLED_PREPARE,
 	CPUHP_POWERPC_PMAC_PREPARE,
+	CPUHP_POWERPC_MMU_CTX_PREPARE,
 	CPUHP_NOTIFY_PREPARE,
 	CPUHP_TIMERS_DEAD,
 	CPUHP_BRINGUP_CPU,