CPU HOTPLUG: avoid hotadd when proper possible_map isn't specified

cpu-hot-add should be fail if cpu is not set in cpu_possible_map.  If go
ahead, the system will panic soon.

Especially, arch which requires additional_cpus= parameter should handle
this.  Tested on ia64.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/cpu.c

@@ -265,6 +265,15 @@ out_notify:
 int __cpuinit cpu_up(unsigned int cpu)
 {
 	int err = 0;
+	if (!cpu_isset(cpu, cpu_possible_map)) {
+		printk(KERN_ERR "can't online cpu %d because it is not "
+			"configured as may-hotadd at boot time\n", cpu);
+#if defined(CONFIG_IA64) || defined(CONFIG_X86_64) || defined(CONFIG_S390)
+		printk(KERN_ERR "please check additional_cpus= boot "
+				"parameter\n");
+#endif
+		return -EINVAL;
+	}
 
 	mutex_lock(&cpu_add_remove_lock);
 	if (cpu_hotplug_disabled)