8292202: modules_do is called without Module_lock

Reviewed-by: iklam, coleenp

Author: calvinccheung

src/hotspot/share/classfile/classLoaderExt.cpp

@@ -82,20 +82,34 @@ void ClassLoaderExt::setup_app_search_path(JavaThread* current) {
 
 void ClassLoaderExt::process_module_table(JavaThread* current, ModuleEntryTable* met) {
   ResourceMark rm(current);
-  class Process : public ModuleClosure {
+  GrowableArray<char*>* module_paths = new GrowableArray<char*>(5);
+
+  class ModulePathsGatherer : public ModuleClosure {
     JavaThread* _current;
+    GrowableArray<char*>* _module_paths;
    public:
-    Process(JavaThread* current) : _current(current) {}
+    ModulePathsGatherer(JavaThread* current, GrowableArray<char*>* module_paths) :
+      _current(current), _module_paths(module_paths) {}
     void do_module(ModuleEntry* m) {
       char* path = m->location()->as_C_string();
       if (strncmp(path, "file:", 5) == 0) {
         path = ClassLoader::skip_uri_protocol(path);
-        ClassLoader::setup_module_search_path(_current, path);
+        char* path_copy = NEW_RESOURCE_ARRAY(char, strlen(path) + 1);
+        strcpy(path_copy, path);
+        _module_paths->append(path_copy);
       }
     }
   };
-  Process process(current);
-  met->modules_do(&process);
+
+  ModulePathsGatherer gatherer(current, module_paths);
+  {
+    MutexLocker ml(Module_lock);
+    met->modules_do(&gatherer);
+  }
+
+  for (int i = 0; i < module_paths->length(); i++) {
+    ClassLoader::setup_module_search_path(current, module_paths->at(i));
+  }
 }
 
 void ClassLoaderExt::setup_module_paths(JavaThread* current) {

src/hotspot/share/classfile/moduleEntry.cpp

@@ -694,13 +694,15 @@ void ModuleEntryTable::modules_do(void f(ModuleEntry*)) {
   auto do_f = [&] (const SymbolHandle& key, ModuleEntry*& entry) {
     f(entry);
   };
+  assert_lock_strong(Module_lock);
   _table.iterate_all(do_f);
 }
 
 void ModuleEntryTable::modules_do(ModuleClosure* closure) {
   auto do_f = [&] (const SymbolHandle& key, ModuleEntry*& entry) {
     closure->do_module(entry);
   };
+  assert_lock_strong(Module_lock);
   _table.iterate_all(do_f);
 }