src/hotspot/share/classfile/systemDictionary.cpp

@@ -1853,47 +1853,53 @@
 // Note: anonymous classes are not in the SD.
 bool SystemDictionary::do_unloading(GCTimer* gc_timer,
                                     bool do_cleaning) {
 
   bool unloading_occurred;
+  bool is_concurrent = SafepointSynchronize::is_at_safepoint();
   {
     GCTraceTime(Debug, gc, phases) t("ClassLoaderData", gc_timer);
-
+    assert_locked_or_safepoint(ClassLoaderDataGraph_lock);  // caller locks.
     // First, mark for unload all ClassLoaderData referencing a dead class loader.
     unloading_occurred = ClassLoaderDataGraph::do_unloading(do_cleaning);
+
     if (unloading_occurred) {
+      MutexLockerEx ml2(is_concurrent ? Module_lock : NULL);
       JFR_ONLY(Jfr::on_unloading_classes();)
+      MutexLockerEx ml1(is_concurrent ? SystemDictionary_lock : NULL);
       ClassLoaderDataGraph::clean_module_and_package_info();
     }
   }
 
-  // TODO: just return if !unloading_occurred.
+  if (do_cleaning) {
+    GCTraceTime(Debug, gc, phases) t("ResolvedMethodTable", gc_timer);
+    ResolvedMethodTable::trigger_cleanup();
+  }
+
   if (unloading_occurred) {
     {
       GCTraceTime(Debug, gc, phases) t("SymbolTable", gc_timer);
       // Check if there's work to do in the SymbolTable
       SymbolTable::do_check_concurrent_work();
     }
 
     {
+      MutexLockerEx ml(is_concurrent ? SystemDictionary_lock : NULL);
       GCTraceTime(Debug, gc, phases) t("Dictionary", gc_timer);
       constraints()->purge_loader_constraints();
       resolution_errors()->purge_resolution_errors();
     }
-  }
 
   {
     GCTraceTime(Debug, gc, phases) t("ProtectionDomainCacheTable", gc_timer);
     // Oops referenced by the protection domain cache table may get unreachable independently
     // of the class loader (eg. cached protection domain oops). So we need to
     // explicitly unlink them here.
+      // All protection domain oops are linked to the caller class, so if nothing
+      // unloads, this is not needed.
     _pd_cache_table->trigger_cleanup();
   }
-
-  if (do_cleaning) {
-    GCTraceTime(Debug, gc, phases) t("ResolvedMethodTable", gc_timer);
-    ResolvedMethodTable::trigger_cleanup();
   }
 
   return unloading_occurred;
 }