driver core / cpu: Check if NUMA node is valid before bringing CPU up

There is a potential race condition between cpu_subsys_online()
and either acpi_processor_remove() or remove_memory() that execute
try_offline_node().  Namely, it is possible that cpu_subsys_online()
will run right after the CPUs NUMA node has been put offline and
cpu_to_node() executed by it will return NUMA_NO_NODE (-1).  In
that case the CPU is gone and it doesn't make sense to call cpu_up()
for it, so make cpu_subsys_online() return -ENODEV then.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: NToshi Kani <toshi.kani@hp.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/cpu.c

@@ -43,11 +43,14 @@ static int __ref cpu_subsys_online(struct device *dev)
 	struct cpu *cpu = container_of(dev, struct cpu, dev);
 	int cpuid = dev->id;
 	int from_nid, to_nid;
-	int ret;
+	int ret = -ENODEV;
 
 	cpu_hotplug_driver_lock();
 
 	from_nid = cpu_to_node(cpuid);
+	if (from_nid == NUMA_NO_NODE)
+		goto out;
+
 	ret = cpu_up(cpuid);
 	/*
 	 * When hot adding memory to memoryless node and enabling a cpu
@@ -57,6 +60,7 @@ static int __ref cpu_subsys_online(struct device *dev)
 	if (from_nid != to_nid)
 		change_cpu_under_node(cpu, from_nid, to_nid);
 
+ out:
 	cpu_hotplug_driver_unlock();
 	return ret;
 }