x86/vdso: 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>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153332.987560239@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/entry/vdso/vma.c

@@ -294,15 +294,9 @@ static void vgetcpu_cpu_init(void *arg)
 	write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
 }
 
-static int
-vgetcpu_cpu_notifier(struct notifier_block *n, unsigned long action, void *arg)
+static int vgetcpu_online(unsigned int cpu)
 {
-	long cpu = (long)arg;
-
-	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN)
-		smp_call_function_single(cpu, vgetcpu_cpu_init, NULL, 1);
-
-	return NOTIFY_DONE;
+	return smp_call_function_single(cpu, vgetcpu_cpu_init, NULL, 1);
 }
 
 static int __init init_vdso(void)
@@ -313,15 +307,9 @@ static int __init init_vdso(void)
 	init_vdso_image(&vdso_image_x32);
 #endif
 
-	cpu_notifier_register_begin();
-
-	on_each_cpu(vgetcpu_cpu_init, NULL, 1);
 	/* notifier priority > KVM */
-	__hotcpu_notifier(vgetcpu_cpu_notifier, 30);
-
-	cpu_notifier_register_done();
-
-	return 0;
+	return cpuhp_setup_state(CPUHP_AP_X86_VDSO_VMA_ONLINE,
+				 "AP_X86_VDSO_VMA_ONLINE", vgetcpu_online, NULL);
 }
 subsys_initcall(init_vdso);
 #endif /* CONFIG_X86_64 */

include/linux/cpuhotplug.h

@@ -14,6 +14,7 @@ enum cpuhp_state {
 	CPUHP_TEARDOWN_CPU,
 	CPUHP_AP_ONLINE_IDLE,
 	CPUHP_AP_SMPBOOT_THREADS,
+	CPUHP_AP_X86_VDSO_VMA_ONLINE,
 	CPUHP_AP_NOTIFY_ONLINE,
 	CPUHP_AP_ONLINE_DYN,
 	CPUHP_AP_ONLINE_DYN_END		= CPUHP_AP_ONLINE_DYN + 30,