Linux Kernel Markers: fix marker mutex not taken upon module load

Upon module load, we must take the markers mutex. It implies that the marker
mutex must be nested inside the module mutex.

It implies changing the nesting order : now the marker mutex nests inside the
module mutex. Make the necessary changes to reverse the order in which the
mutexes are taken.

Includes some cleanup from Dave Hansen <[e-mail]>.

Signed-off-by: Mathieu Desnoyers <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

kernel/marker.c

···
 extern struct marker __stop___markers[];
 
 /*
- * module_mutex nests inside markers_mutex. Markers mutex protects the builtin
+ * markers_mutex nests inside module_mutex. Markers mutex protects the builtin
  * and module markers, the hash table and deferred_sync.
  */
 static DEFINE_MUTEX(markers_mutex);
···
  * @refcount: number of references left to the given probe_module (out)
  *
  * Updates the probe callback corresponding to a range of markers.
- * Must be called with markers_mutex held.
  */
 void marker_update_probe_range(struct marker *begin,
 	struct marker *end, struct module *probe_module,
···
 	struct marker *iter;
 	struct marker_entry *mark_entry;
 
+	mutex_lock(&markers_mutex);
 	for (iter = begin; iter < end; iter++) {
 		mark_entry = get_marker(iter->name);
 		if (mark_entry && mark_entry->refcount) {
···
 			disable_marker(iter);
 		}
 	}
+	mutex_unlock(&markers_mutex);
 }
 
 /*
···
 {
 	int refcount = 0;
 
-	mutex_lock(&markers_mutex);
 	/* Core kernel markers */
 	marker_update_probe_range(__start___markers,
 			__stop___markers, probe_module, &refcount);
···
 		synchronize_sched();
 		deferred_sync = 0;
 	}
-	mutex_unlock(&markers_mutex);
 }
 
 /**
···
 			marker_probe_func *probe, void *private)
 {
 	struct marker_entry *entry;
-	int ret = 0, need_update = 0;
+	int ret = 0;
 
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
···
 	ret = add_marker(name, format, probe, private);
 	if (ret)
 		goto end;
-	need_update = 1;
+	mutex_unlock(&markers_mutex);
+	marker_update_probes(NULL);
+	return ret;
 end:
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(NULL);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(marker_probe_register);
···
 	struct module *probe_module;
 	struct marker_entry *entry;
 	void *private;
-	int need_update = 0;
 
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
···
 	probe_module = __module_text_address((unsigned long)entry->probe);
 	private = remove_marker(name);
 	deferred_sync = 1;
-	need_update = 1;
+	mutex_unlock(&markers_mutex);
+	marker_update_probes(probe_module);
+	return private;
 end:
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(probe_module);
 	return private;
 }
 EXPORT_SYMBOL_GPL(marker_probe_unregister);
···
 	struct marker_entry *entry;
 	int found = 0;
 	unsigned int i;
-	int need_update = 0;
 
 	mutex_lock(&markers_mutex);
 	for (i = 0; i < MARKER_TABLE_SIZE; i++) {
···
 	probe_module = __module_text_address((unsigned long)entry->probe);
 	private = remove_marker(entry->name);
 	deferred_sync = 1;
-	need_update = 1;
+	mutex_unlock(&markers_mutex);
+	marker_update_probes(probe_module);
+	return private;
 end:
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(probe_module);
 	return private;
 }
 EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
···
 int marker_arm(const char *name)
 {
 	struct marker_entry *entry;
-	int ret = 0, need_update = 0;
+	int ret = 0;
 
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
···
 	 */
 	if (entry->refcount++)
 		goto end;
-	need_update = 1;
 end:
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(NULL);
+	marker_update_probes(NULL);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(marker_arm);
···
 int marker_disarm(const char *name)
 {
 	struct marker_entry *entry;
-	int ret = 0, need_update = 0;
+	int ret = 0;
 
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
···
 		ret = -EPERM;
 		goto end;
 	}
-	need_update = 1;
 end:
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(NULL);
+	marker_update_probes(NULL);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(marker_disarm);