3 files changed, 62 insertions, 15 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
diff --git a/kernel/profile.c b/kernel/profile.c
index 1b266dbe755a..cb980f0c731b 100644
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -591,18 +591,28 @@ out_cleanup:
 int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
 {
         struct proc_dir_entry *entry;
+        int err = 0;
 
         if (!prof_on)
                 return 0;
-        if (create_hash_tables())
-                return -ENOMEM;
+
+        cpu_notifier_register_begin();
+
+        if (create_hash_tables()) {
+                err = -ENOMEM;
+                goto out;
+        }
+
         entry = proc_create("profile", S_IWUSR | S_IRUGO,
                             NULL, &proc_profile_operations);
         if (!entry)
-                return 0;
+                goto out;
         proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
-        hotcpu_notifier(profile_cpu_callback, 0);
-        return 0;
+        __hotcpu_notifier(profile_cpu_callback, 0);
+
+out:
+        cpu_notifier_register_done();
+        return err;
 }
 subsys_initcall(create_proc_profile);
 #endif /* CONFIG_PROC_FS */
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index fc4da2d97f9b..c634868c2921 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1301,7 +1301,7 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
          * In that off case, we need to allocate for all possible cpus.
          */
 #ifdef CONFIG_HOTPLUG_CPU
-        get_online_cpus();
+        cpu_notifier_register_begin();
         cpumask_copy(buffer->cpumask, cpu_online_mask);
 #else
         cpumask_copy(buffer->cpumask, cpu_possible_mask);
@@ -1324,10 +1324,10 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
 #ifdef CONFIG_HOTPLUG_CPU
         buffer->cpu_notify.notifier_call = rb_cpu_notify;
         buffer->cpu_notify.priority = 0;
-        register_cpu_notifier(&buffer->cpu_notify);
+        __register_cpu_notifier(&buffer->cpu_notify);
+        cpu_notifier_register_done();
 #endif
 
-        put_online_cpus();
         mutex_init(&buffer->mutex);
 
         return buffer;
@@ -1341,7 +1341,9 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
 
  fail_free_cpumask:
         free_cpumask_var(buffer->cpumask);
-        put_online_cpus();
+#ifdef CONFIG_HOTPLUG_CPU
+        cpu_notifier_register_done();
+#endif
 
  fail_free_buffer:
         kfree(buffer);
@@ -1358,16 +1360,17 @@ ring_buffer_free(struct ring_buffer *buffer)
 {
         int cpu;
 
-        get_online_cpus();
-
 #ifdef CONFIG_HOTPLUG_CPU
-        unregister_cpu_notifier(&buffer->cpu_notify);
+        cpu_notifier_register_begin();
+        __unregister_cpu_notifier(&buffer->cpu_notify);
 #endif
 
         for_each_buffer_cpu(buffer, cpu)
                 rb_free_cpu_buffer(buffer->buffers[cpu]);
 
-        put_online_cpus();
+#ifdef CONFIG_HOTPLUG_CPU
+        cpu_notifier_register_done();
+#endif
 
         kfree(buffer->buffers);
         free_cpumask_var(buffer->cpumask);