8007725: NPG: Klass::restore_unshareable_info() triggers assert(k->java_mirror() == NULL)

Check for exception during SystemDictionary::resolve_instance_class_or_null() and clean up.

Reviewed-by: coleenp, acorn, hseigel, minqi

hotspot/src/share/vm/classfile/classLoaderData.cpp

@@ -105,6 +105,7 @@ void ClassLoaderData::oops_do(OopClosure* f, KlassClosure* klass_closure, bool m
 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
     klass_closure->do_klass(k);
+    assert(k != k->next_link(), "no loops!");
   }
 }
 
@@ -113,6 +114,7 @@ void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
     if (k->oop_is_instance()) {
       f(InstanceKlass::cast(k));
     }
+    assert(k != k->next_link(), "no loops!");
   }
 }
 
@@ -258,6 +260,7 @@ void ClassLoaderData::remove_class(Klass* scratch_class) {
       return;
     }
     prev = k;
+    assert(k != k->next_link(), "no loops!");
   }
   ShouldNotReachHere();   // should have found this class!!
 }
@@ -439,6 +442,7 @@ void ClassLoaderData::dump(outputStream * const out) {
     while (k != NULL) {
       out->print_cr("klass "PTR_FORMAT", %s, CT: %d, MUT: %d", k, k->name()->as_C_string(),
           k->has_modified_oops(), k->has_accumulated_modified_oops());
+      assert(k != k->next_link(), "no loops!");
       k = k->next_link();
     }
   }
@@ -465,6 +469,7 @@ void ClassLoaderData::verify() {
   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
     guarantee(k->class_loader_data() == this, "Must be the same");
     k->verify();
+    assert(k != k->next_link(), "no loops!");
   }
 }
 

hotspot/src/share/vm/classfile/systemDictionary.cpp

@@ -804,6 +804,32 @@ Klass* SystemDictionary::resolve_instance_class_or_null(Symbol* name, Handle cla
       }
     } // load_instance_class loop
 
+    if (HAS_PENDING_EXCEPTION) {
+      // An exception, such as OOM could have happened at various places inside
+      // load_instance_class. We might have partially initialized a shared class
+      // and need to clean it up.
+      if (class_loader.is_null()) {
+        // In some cases k may be null. Let's find the shared class again.
+        instanceKlassHandle ik(THREAD, find_shared_class(name));
+        if (ik.not_null()) {
+          if (ik->class_loader_data() == NULL) {
+            // We didn't go as far as Klass::restore_unshareable_info(),
+            // so nothing to clean up.
+          } else {
+            MutexLocker mu(SystemDictionary_lock, THREAD);
+            Klass* kk = find_class(name, ik->class_loader_data());
+            if (kk != NULL) {
+              // No clean up is needed if the shared class has been entered
+              // into system dictionary, as load_shared_class() won't be called
+              // again.
+            } else {
+              clean_up_shared_class(ik, class_loader, THREAD);
+            }
+          }
+        }
+      }
+    }
+
     if (load_instance_added == true) {
       // clean up placeholder entries for LOAD_INSTANCE success or error
       // This brackets the SystemDictionary updates for both defining
@@ -1140,11 +1166,6 @@ instanceKlassHandle SystemDictionary::load_shared_class(
   return load_shared_class(ik, class_loader, THREAD);
 }
 
-// Note well!  Changes to this method may affect oop access order
-// in the shared archive.  Please take care to not make changes that
-// adversely affect cold start time by changing the oop access order
-// that is specified in dump.cpp MarkAndMoveOrderedReadOnly and
-// MarkAndMoveOrderedReadWrite closures.
 instanceKlassHandle SystemDictionary::load_shared_class(
                  instanceKlassHandle ik, Handle class_loader, TRAPS) {
   assert(class_loader.is_null(), "non-null classloader for shared class?");
@@ -1205,6 +1226,19 @@ instanceKlassHandle SystemDictionary::load_shared_class(
   return ik;
 }
 
+void SystemDictionary::clean_up_shared_class(instanceKlassHandle ik, Handle class_loader, TRAPS) {
+  // Updating methods must be done under a lock so multiple
+  // threads don't update these in parallel
+  // Shared classes are all currently loaded by the bootstrap
+  // classloader, so this will never cause a deadlock on
+  // a custom class loader lock.
+  {
+    Handle lockObject = compute_loader_lock_object(class_loader, THREAD);
+    check_loader_lock_contention(lockObject, THREAD);
+    ObjectLocker ol(lockObject, THREAD, true);
+    ik->remove_unshareable_info();
+  }
+}
 
 instanceKlassHandle SystemDictionary::load_instance_class(Symbol* class_name, Handle class_loader, TRAPS) {
   instanceKlassHandle nh = instanceKlassHandle(); // null Handle

hotspot/src/share/vm/classfile/systemDictionary.hpp

@@ -621,6 +621,7 @@ private:
                                                Handle class_loader, TRAPS);
   static instanceKlassHandle load_shared_class(instanceKlassHandle ik,
                                                Handle class_loader, TRAPS);
+  static void clean_up_shared_class(instanceKlassHandle ik, Handle class_loader, TRAPS);
   static instanceKlassHandle load_instance_class(Symbol* class_name, Handle class_loader, TRAPS);
   static Handle compute_loader_lock_object(Handle class_loader, TRAPS);
   static void check_loader_lock_contention(Handle loader_lock, TRAPS);

hotspot/src/share/vm/oops/klass.cpp

@@ -486,6 +486,12 @@ void Klass::oops_do(OopClosure* cl) {
 }
 
 void Klass::remove_unshareable_info() {
+  if (!DumpSharedSpaces) {
+    // Clean up after OOM during class loading
+    if (class_loader_data() != NULL) {
+      class_loader_data()->remove_class(this);
+    }
+  }
   set_subklass(NULL);
   set_next_sibling(NULL);
   // Clear the java mirror

hotspot/src/share/vm/oops/method.cpp

@@ -798,7 +798,15 @@ void Method::unlink_method() {
   backedge_counter()->reset();
   _adapter = NULL;
   _from_compiled_entry = NULL;
-  assert(_method_data == NULL, "unexpected method data?");
+
+  // In case of DumpSharedSpaces, _method_data should always be NULL.
+  //
+  // During runtime (!DumpSharedSpaces), when we are cleaning a
+  // shared class that failed to load, this->link_method() may
+  // have already been called (before an exception happened), so
+  // this->_method_data may not be NULL.
+  assert(!DumpSharedSpaces || _method_data == NULL, "unexpected method data?");
+
   set_method_data(NULL);
   set_interpreter_throwout_count(0);
   set_interpreter_invocation_count(0);