1 files changed, 36 insertions, 2 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index deff2e693766..a9e710eef0e2 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -19,6 +19,7 @@
 #include <linux/mutex.h>
 #include <linux/gfp.h>
 #include <linux/suspend.h>
+#include <linux/lockdep.h>
 
 #include "smpboot.h"
 
@@ -27,18 +28,23 @@
 static DEFINE_MUTEX(cpu_add_remove_lock);
 
 /*
- * The following two API's must be used when attempting
- * to serialize the updates to cpu_online_mask, cpu_present_mask.
+ * The following two APIs (cpu_maps_update_begin/done) must be used when
+ * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
+ * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
+ * hotplug callback (un)registration performed using __register_cpu_notifier()
+ * or __unregister_cpu_notifier().
  */
 void cpu_maps_update_begin(void)
 {
         mutex_lock(&cpu_add_remove_lock);
 }
+EXPORT_SYMBOL(cpu_notifier_register_begin);
 
 void cpu_maps_update_done(void)
 {
         mutex_unlock(&cpu_add_remove_lock);
 }
+EXPORT_SYMBOL(cpu_notifier_register_done);
 
 static RAW_NOTIFIER_HEAD(cpu_chain);
 
@@ -57,17 +63,30 @@ static struct {
          * an ongoing cpu hotplug operation.
          */
         int refcount;
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+        struct lockdep_map dep_map;
+#endif
 } cpu_hotplug = {
         .active_writer = NULL,
         .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
         .refcount = 0,
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+        .dep_map = {.name = "cpu_hotplug.lock" },
+#endif
 };
 
+/* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
+#define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
+#define cpuhp_lock_acquire()      lock_map_acquire(&cpu_hotplug.dep_map)
+#define cpuhp_lock_release()      lock_map_release(&cpu_hotplug.dep_map)
+
 void get_online_cpus(void)
 {
         might_sleep();
         if (cpu_hotplug.active_writer == current)
                 return;
+        cpuhp_lock_acquire_read();
         mutex_lock(&cpu_hotplug.lock);
         cpu_hotplug.refcount++;
         mutex_unlock(&cpu_hotplug.lock);
@@ -87,6 +106,7 @@ void put_online_cpus(void)
         if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
                 wake_up_process(cpu_hotplug.active_writer);
         mutex_unlock(&cpu_hotplug.lock);
+        cpuhp_lock_release();
 
 }
 EXPORT_SYMBOL_GPL(put_online_cpus);
@@ -117,6 +137,7 @@ void cpu_hotplug_begin(void)
 {
         cpu_hotplug.active_writer = current;
 
+        cpuhp_lock_acquire();
         for (;;) {
                 mutex_lock(&cpu_hotplug.lock);
                 if (likely(!cpu_hotplug.refcount))
@@ -131,6 +152,7 @@ void cpu_hotplug_done(void)
 {
         cpu_hotplug.active_writer = NULL;
         mutex_unlock(&cpu_hotplug.lock);
+        cpuhp_lock_release();
 }
 
 /*
@@ -166,6 +188,11 @@ int __ref register_cpu_notifier(struct notifier_block *nb)
         return ret;
 }
 
+int __ref __register_cpu_notifier(struct notifier_block *nb)
+{
+        return raw_notifier_chain_register(&cpu_chain, nb);
+}
+
 static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
                         int *nr_calls)
 {
@@ -189,6 +216,7 @@ static void cpu_notify_nofail(unsigned long val, void *v)
         BUG_ON(cpu_notify(val, v));
 }
 EXPORT_SYMBOL(register_cpu_notifier);
+EXPORT_SYMBOL(__register_cpu_notifier);
 
 void __ref unregister_cpu_notifier(struct notifier_block *nb)
 {
@@ -198,6 +226,12 @@ void __ref unregister_cpu_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL(unregister_cpu_notifier);
 
+void __ref __unregister_cpu_notifier(struct notifier_block *nb)
+{
+        raw_notifier_chain_unregister(&cpu_chain, nb);
+}
+EXPORT_SYMBOL(__unregister_cpu_notifier);
+
 /**
  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
  * @cpu: a CPU id