8252794: Creation of JNIMethodBlock should be done with a leaf lock

Reviewed-by: coleenp, dholmes

Author: robehn

src/hotspot/share/oops/method.cpp

@@ -2185,9 +2185,9 @@ void Method::ensure_jmethod_ids(ClassLoaderData* loader_data, int capacity) {
   ClassLoaderData* cld = loader_data;
   if (!SafepointSynchronize::is_at_safepoint()) {
     // Have to add jmethod_ids() to class loader data thread-safely.
-    // Also have to add the method to the list safely, which the cld lock
+    // Also have to add the method to the list safely, which the lock
     // protects as well.
-    MutexLocker ml(cld->metaspace_lock(),  Mutex::_no_safepoint_check_flag);
+    MutexLocker ml(JmethodIdCreation_lock,  Mutex::_no_safepoint_check_flag);
     if (cld->jmethod_ids() == NULL) {
       cld->set_jmethod_ids(new JNIMethodBlock(capacity));
     } else {
@@ -2209,9 +2209,9 @@ jmethodID Method::make_jmethod_id(ClassLoaderData* loader_data, Method* m) {
 
   if (!SafepointSynchronize::is_at_safepoint()) {
     // Have to add jmethod_ids() to class loader data thread-safely.
-    // Also have to add the method to the list safely, which the cld lock
+    // Also have to add the method to the list safely, which the lock
     // protects as well.
-    MutexLocker ml(cld->metaspace_lock(),  Mutex::_no_safepoint_check_flag);
+    MutexLocker ml(JmethodIdCreation_lock,  Mutex::_no_safepoint_check_flag);
     if (cld->jmethod_ids() == NULL) {
       cld->set_jmethod_ids(new JNIMethodBlock());
     }

src/hotspot/share/runtime/mutexLocker.cpp

@@ -253,7 +253,7 @@ void mutex_init() {
     Notification_lock = Service_lock;
   }
 
-  def(JmethodIdCreation_lock       , PaddedMutex  , leaf,        true,  _safepoint_check_never); // used for creating jmethodIDs.
+  def(JmethodIdCreation_lock       , PaddedMutex  , special-2,   true,  _safepoint_check_never); // used for creating jmethodIDs.
 
   def(SystemDictionary_lock        , PaddedMonitor, leaf,        true,  _safepoint_check_always);
   def(ProtectionDomainSet_lock     , PaddedMutex  , leaf-1,      true,  _safepoint_check_never);