src/share/vm/runtime/thread.cpp

@@ -1805,13 +1805,20 @@
   // held by this thread must be released.  A detach operation must only
   // get here if there are no Java frames on the stack.  Therefore, any
   // owned monitors at this point MUST be JNI-acquired monitors which are
   // pre-inflated and in the monitor cache.
   //
-  // ensure_join() ignores IllegalThreadStateExceptions, and so does this.
-  if (exit_type == jni_detach && JNIDetachReleasesMonitors) {
-    assert(!this->has_last_Java_frame(), "detaching with Java frames?");
+  // Optionally release any monitors for regular JavaThread exits. This
+  // is provided as a work around for any bugs in monitor enter-exit
+  // matching. This can be expensive so it is not enabled by default.
+  //
+  // ensure_join() ignores IllegalThreadStateExceptions, and so does
+  // ObjectSynchronizer::release_monitors_owned_by_thread().
+  if ((exit_type == jni_detach && JNIDetachReleasesMonitors) ||
+      JavaThreadExitReleasesMonitors) {
+    assert(!this->has_last_Java_frame(),
+           "should not have a Java frame when detaching or exiting");
     ObjectSynchronizer::release_monitors_owned_by_thread(this);
     assert(!this->has_pending_exception(), "release_monitors should have cleared");
   }
 
   // These things needs to be done while we are still a Java Thread. Make sure that thread