hotplug / x86: Add hotplug lock to missing places

lock_device_hotplug[_sysfs]() serializes CPU & Memory online/offline
and hotplug operations.  However, this lock is not held in the debug
interfaces below that initiate CPU online/offline operations.

 - _debug_hotplug_cpu(), cpu0 hotplug test interface enabled by
   CONFIG_DEBUG_HOTPLUG_CPU0.
 - cpu_probe_store() and cpu_release_store(), cpu hotplug test interface
   enabled by CONFIG_ARCH_CPU_PROBE_RELEASE.

This patch changes the above interfaces to hold lock_device_hotplug().

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

arch/x86/kernel/topology.c

@@ -65,6 +65,7 @@ int __ref _debug_hotplug_cpu(int cpu, int action)
 	if (!cpu_is_hotpluggable(cpu))
 		return -EINVAL;
 
+	lock_device_hotplug();
 	cpu_hotplug_driver_lock();
 
 	switch (action) {
@@ -91,6 +92,7 @@ int __ref _debug_hotplug_cpu(int cpu, int action)
 	}
 
 	cpu_hotplug_driver_unlock();
+	unlock_device_hotplug();
 
 	return ret;
 }

drivers/base/cpu.c

@@ -93,7 +93,17 @@ static ssize_t cpu_probe_store(struct device *dev,
 			       const char *buf,
 			       size_t count)
 {
-	return arch_cpu_probe(buf, count);
+	ssize_t cnt;
+	int ret;
+
+	ret = lock_device_hotplug_sysfs();
+	if (ret)
+		return ret;
+
+	cnt = arch_cpu_probe(buf, count);
+
+	unlock_device_hotplug();
+	return cnt;
 }
 
 static ssize_t cpu_release_store(struct device *dev,
@@ -101,7 +111,17 @@ static ssize_t cpu_release_store(struct device *dev,
 				 const char *buf,
 				 size_t count)
 {
-	return arch_cpu_release(buf, count);
+	ssize_t cnt;
+	int ret;
+
+	ret = lock_device_hotplug_sysfs();
+	if (ret)
+		return ret;
+
+	cnt = arch_cpu_release(buf, count);
+
+	unlock_device_hotplug();
+	return cnt;
 }
 
 static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);