--- a/hotspot/src/share/vm/ci/ciEnv.cpp	Thu Jan 27 16:11:27 2011 -0800
+++ b/hotspot/src/share/vm/ci/ciEnv.cpp	Mon Jan 31 17:48:21 2011 -0800
@@ -412,13 +412,16 @@
     fail_type = _unloaded_ciinstance_klass;
   }
   KlassHandle found_klass;
-  if (!require_local) {
-    klassOop kls = SystemDictionary::find_constrained_instance_or_array_klass(
-        sym, loader, KILL_COMPILE_ON_FATAL_(fail_type));
-    found_klass = KlassHandle(THREAD, kls);
-  } else {
-    klassOop kls = SystemDictionary::find_instance_or_array_klass(
-        sym, loader, domain, KILL_COMPILE_ON_FATAL_(fail_type));
+  {
+    MutexLocker ml(Compile_lock);
+    klassOop kls;
+    if (!require_local) {
+      kls = SystemDictionary::find_constrained_instance_or_array_klass(sym, loader,
+                                                                       KILL_COMPILE_ON_FATAL_(fail_type));
+    } else {
+      kls = SystemDictionary::find_instance_or_array_klass(sym, loader, domain,
+                                                           KILL_COMPILE_ON_FATAL_(fail_type));
+    }
     found_klass = KlassHandle(THREAD, kls);
   }
 

--- a/hotspot/src/share/vm/ci/ciInstanceKlass.cpp	Thu Jan 27 16:11:27 2011 -0800
+++ b/hotspot/src/share/vm/ci/ciInstanceKlass.cpp	Mon Jan 31 17:48:21 2011 -0800
@@ -46,6 +46,7 @@
   ciKlass(h_k), _non_static_fields(NULL)
 {
   assert(get_Klass()->oop_is_instance(), "wrong type");
+  assert(get_instanceKlass()->is_loaded(), "must be at least loaded");
   instanceKlass* ik = get_instanceKlass();
 
   AccessFlags access_flags = ik->access_flags();

--- a/hotspot/src/share/vm/classfile/loaderConstraints.cpp	Thu Jan 27 16:11:27 2011 -0800
+++ b/hotspot/src/share/vm/classfile/loaderConstraints.cpp	Mon Jan 31 17:48:21 2011 -0800
@@ -322,8 +322,14 @@
 klassOop LoaderConstraintTable::find_constrained_klass(Symbol* name,
                                                        Handle loader) {
   LoaderConstraintEntry *p = *(find_loader_constraint(name, loader));
-  if (p != NULL && p->klass() != NULL)
+  if (p != NULL && p->klass() != NULL) {
+    if (Klass::cast(p->klass())->oop_is_instance() && !instanceKlass::cast(p->klass())->is_loaded()) {
+      // Only return fully loaded classes.  Classes found through the
+      // constraints might still be in the process of loading.
+      return NULL;
+    }
     return p->klass();
+  }
 
   // No constraints, or else no klass loaded yet.
   return NULL;

--- a/hotspot/src/share/vm/classfile/systemDictionary.cpp	Thu Jan 27 16:11:27 2011 -0800
+++ b/hotspot/src/share/vm/classfile/systemDictionary.cpp	Mon Jan 31 17:48:21 2011 -0800
@@ -1690,6 +1690,8 @@
 
 void SystemDictionary::add_to_hierarchy(instanceKlassHandle k, TRAPS) {
   assert(k.not_null(), "just checking");
+  assert_locked_or_safepoint(Compile_lock);
+
   // Link into hierachy. Make sure the vtables are initialized before linking into
   k->append_to_sibling_list();                    // add to superklass/sibling list
   k->process_interfaces(THREAD);                  // handle all "implements" declarations
@@ -2152,6 +2154,9 @@
 }
 
 
+// Try to find a class name using the loader constraints.  The
+// loader constraints might know about a class that isn't fully loaded
+// yet and these will be ignored.
 klassOop SystemDictionary::find_constrained_instance_or_array_klass(
                     Symbol* class_name, Handle class_loader, TRAPS) {