x86, therm_throt.c: Remove unused therm_cpu_lock

After fixing the CPU hotplug callback registration code, the callbacks
invoked for each online CPU, during the initialization phase in
thermal_throttle_init_device(), can no longer race with the actual CPU
hotplug notifier callbacks (in thermal_throttle_cpu_callback). Hence the
therm_cpu_lock is unnecessary now. Remove it.

Cc: Tony Luck <tony.luck@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

arch/x86/kernel/cpu/mcheck/therm_throt.c

@@ -271,9 +271,6 @@ static void thermal_throttle_remove_dev(struct device *dev)
 	sysfs_remove_group(&dev->kobj, &thermal_attr_group);
 }
 
-/* Mutex protecting device creation against CPU hotplug: */
-static DEFINE_MUTEX(therm_cpu_lock);
-
 /* Get notified when a cpu comes on/off. Be hotplug friendly. */
 static int
 thermal_throttle_cpu_callback(struct notifier_block *nfb,
@@ -289,18 +286,14 @@ thermal_throttle_cpu_callback(struct notifier_block *nfb,
 	switch (action) {
 	case CPU_UP_PREPARE:
 	case CPU_UP_PREPARE_FROZEN:
-		mutex_lock(&therm_cpu_lock);
 		err = thermal_throttle_add_dev(dev, cpu);
-		mutex_unlock(&therm_cpu_lock);
 		WARN_ON(err);
 		break;
 	case CPU_UP_CANCELED:
 	case CPU_UP_CANCELED_FROZEN:
 	case CPU_DEAD:
 	case CPU_DEAD_FROZEN:
-		mutex_lock(&therm_cpu_lock);
 		thermal_throttle_remove_dev(dev);
-		mutex_unlock(&therm_cpu_lock);
 		break;
 	}
 	return notifier_from_errno(err);
@@ -321,17 +314,11 @@ static __init int thermal_throttle_init_device(void)
 
 	cpu_notifier_register_begin();
 
-#ifdef CONFIG_HOTPLUG_CPU
-	mutex_lock(&therm_cpu_lock);
-#endif
 	/* connect live CPUs to sysfs */
 	for_each_online_cpu(cpu) {
 		err = thermal_throttle_add_dev(get_cpu_device(cpu), cpu);
 		WARN_ON(err);
 	}
-#ifdef CONFIG_HOTPLUG_CPU
-	mutex_unlock(&therm_cpu_lock);
-#endif
 
 	__register_hotcpu_notifier(&thermal_throttle_cpu_notifier);
 	cpu_notifier_register_done();