8222893: markOopDesc::print_on() is a bit confused

Add print_on for ObjectMonitor and make markOop printing sensible and add test.

Reviewed-by: dcubed, pchilanomate

src/hotspot/share/oops/klass.cpp

@@ -733,8 +733,9 @@ void Klass::print_on(outputStream* st) const {
   st->cr();
 }
 
+#define BULLET  " - "
+
 void Klass::oop_print_on(oop obj, outputStream* st) {
-  ResourceMark rm;
   // print title
   st->print_cr("%s ", internal_name());
   obj->print_address_on(st);
@@ -742,10 +743,13 @@ void Klass::oop_print_on(oop obj, outputStream* st) {
   if (WizardMode) {
      // print header
      obj->mark()->print_on(st);
+     st->cr();
+     st->print(BULLET"prototype_header: " INTPTR_FORMAT, p2i(_prototype_header));
+     st->cr();
   }
 
   // print class
-  st->print(" - klass: ");
+  st->print(BULLET"klass: ");
   obj->klass()->print_value_on(st);
   st->cr();
 }

src/hotspot/share/oops/markOop.cpp

@@ -25,45 +25,40 @@
 #include "precompiled.hpp"
 #include "oops/markOop.hpp"
 #include "runtime/thread.inline.hpp"
-#include "runtime/objectMonitor.inline.hpp"
+#include "runtime/objectMonitor.hpp"
 
 void markOopDesc::print_on(outputStream* st) const {
-  if (is_marked()) {
+  if (is_marked()) {  // last bits = 11
     st->print(" marked(" INTPTR_FORMAT ")", value());
-  } else if (has_monitor()) {
+  } else if (has_monitor()) {  // last bits = 10
     // have to check has_monitor() before is_locked()
     st->print(" monitor(" INTPTR_FORMAT ")=", value());
     ObjectMonitor* mon = monitor();
     if (mon == NULL) {
       st->print("NULL (this should never be seen!)");
     } else {
-      st->print("{contentions=0x%08x,waiters=0x%08x"
-                ",recursions=" INTPTR_FORMAT ",owner=" INTPTR_FORMAT "}",
-                mon->contentions(), mon->waiters(), mon->recursions(),
-                p2i(mon->owner()));
+      mon->print_on(st);
     }
-  } else if (is_locked()) {
-    st->print(" locked(" INTPTR_FORMAT ")->", value());
-    if (is_neutral()) {
+  } else if (is_locked()) {  // last bits != 01 => 00
+    // thin locked
+    st->print(" locked(" INTPTR_FORMAT ")", value());
+  } else {
+    st->print(" mark(");
+    // Biased bit is 3rd rightmost bit
+    if (is_neutral()) {   // last bits = 001
       st->print("is_neutral");
       if (has_no_hash()) {
         st->print(" no_hash");
       } else {
         st->print(" hash=" INTPTR_FORMAT, hash());
       }
-      st->print(" age=%d", age());
-    } else if (has_bias_pattern()) {
+    } else if (has_bias_pattern()) {  // last bits = 101
       st->print("is_biased");
       JavaThread* jt = biased_locker();
-      st->print(" biased_locker=" INTPTR_FORMAT, p2i(jt));
+      st->print(" biased_locker=" INTPTR_FORMAT " epoch=%d", p2i(jt), bias_epoch());
     } else {
       st->print("??");
     }
-  } else {
-    assert(is_unlocked() || has_bias_pattern(), "just checking");
-    st->print("mark(");
-    if (has_bias_pattern()) st->print("biased,");
-    st->print("hash " INTPTR_FORMAT ",", hash());
-    st->print("age %d)", age());
+    st->print(" age=%d)", age());
   }
 }

src/hotspot/share/runtime/objectMonitor.cpp

@@ -1926,3 +1926,11 @@ void ObjectMonitor::Initialize() {
 
   DEBUG_ONLY(InitDone = true;)
 }
+
+void ObjectMonitor::print_on(outputStream* st) const {
+  // The minimal things to print for markOop printing, more can be added for debugging and logging.
+  st->print("{contentions=0x%08x,waiters=0x%08x"
+            ",recursions=" INTPTR_FORMAT ",owner=" INTPTR_FORMAT "}",
+            contentions(), waiters(), recursions(),
+            p2i(owner()));
+}

src/hotspot/share/runtime/objectMonitor.hpp

@@ -291,6 +291,9 @@ class ObjectMonitor {
   void      notify(TRAPS);
   void      notifyAll(TRAPS);
 
+  void      print() const { print_on(tty); }
+  void      print_on(outputStream* st) const;
+
 // Use the following at your own risk
   intptr_t  complete_exit(TRAPS);
   void      reenter(intptr_t recursions, TRAPS);

test/hotspot/gtest/oops/test_markOop.cpp

@@ -0,0 +1,137 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#include "precompiled.hpp"
+#include "classfile/systemDictionary.hpp"
+#include "memory/resourceArea.hpp"
+#include "memory/universe.hpp"
+#include "oops/oop.inline.hpp"
+#include "runtime/atomic.hpp"
+#include "runtime/interfaceSupport.inline.hpp"
+#include "runtime/orderAccess.hpp"
+#include "runtime/os.hpp"
+#include "runtime/synchronizer.hpp"
+#include "threadHelper.inline.hpp"
+#include "unittest.hpp"
+#include "utilities/globalDefinitions.hpp"
+#include "utilities/ostream.hpp"
+
+static bool test_pattern(stringStream* st, const char* pattern) {
+  return (strstr(st->as_string(), pattern) != NULL);
+}
+
+static void assert_test_pattern(Handle object, const char* pattern) {
+  stringStream st;
+  object->print_on(&st);
+  ASSERT_TRUE(test_pattern(&st, pattern)) << pattern << " not in " << st.as_string();
+}
+
+static void assert_not_test_pattern(Handle object, const char* pattern) {
+  stringStream st;
+  object->print_on(&st);
+  ASSERT_FALSE(test_pattern(&st, pattern)) << pattern << " found in " << st.as_string();
+}
+
+class LockerThread : public JavaTestThread {
+  oop _obj;
+  public:
+  LockerThread(Semaphore* post, oop obj) : JavaTestThread(post), _obj(obj) {}
+  virtual ~LockerThread() {}
+
+  void main_run() {
+    Thread* THREAD = Thread::current();
+    HandleMark hm(THREAD);
+    Handle h_obj(THREAD, _obj);
+    ResourceMark rm(THREAD);
+
+    // Wait gets the lock inflated.
+    // The object will stay locked for the context of 'ol' so the lock will
+    // still be inflated after the notify_all() call. Deflation can't happen
+    // while an ObjectMonitor is "busy" and being locked is the most "busy"
+    // state we have...
+    ObjectLocker ol(h_obj, THREAD);
+    ol.notify_all(THREAD);
+    assert_test_pattern(h_obj, "monitor");
+  }
+};
+
+
+TEST_VM(markOopDesc, printing) {
+  JavaThread* THREAD = JavaThread::current();
+  ThreadInVMfromNative invm(THREAD);
+  ResourceMark rm(THREAD);
+
+  oop obj = SystemDictionary::Byte_klass()->allocate_instance(THREAD);
+
+  FlagSetting fs(WizardMode, true);
+  FlagSetting bf(UseBiasedLocking, true);
+
+  HandleMark hm(THREAD);
+  Handle h_obj(THREAD, obj);
+
+  // Biased locking is initially enabled for this java.lang.Byte object.
+  assert_test_pattern(h_obj, "is_biased");
+
+  // Lock using biased locking.
+  BasicObjectLock lock;
+  lock.set_obj(obj);
+  markOop mark = obj->mark()->incr_bias_epoch();
+  obj->set_mark(mark);
+  ObjectSynchronizer::fast_enter(h_obj, lock.lock(), true, THREAD);
+#ifdef _LP64
+  // Look for the biased_locker in markOop, not prototype_header.
+  assert_not_test_pattern(h_obj, "mark(is_biased biased_locker=0x0000000000000000");
+#endif
+
+  // Same thread tries to lock it again.
+  {
+    ObjectLocker ol(h_obj, THREAD);
+    assert_test_pattern(h_obj, "locked");
+  }
+
+  // This is no longer biased, because ObjectLocker revokes the bias.
+  assert_test_pattern(h_obj, "is_neutral no_hash");
+
+  // Wait gets the lock inflated.
+  {
+    ObjectLocker ol(h_obj, THREAD);
+
+    Semaphore done(0);
+    LockerThread* st;
+    st = new LockerThread(&done, h_obj());
+    st->doit();
+
+    ol.wait(THREAD);
+    assert_test_pattern(h_obj, "monitor");
+  }
+
+  // Make the object older. Not all GCs use this field.
+  Universe::heap()->collect(GCCause::_java_lang_system_gc);
+  if (UseParallelGC) {
+    assert_test_pattern(h_obj, "is_neutral no_hash age 1");
+  }
+
+  // Hash the object then print it.
+  intx hash = h_obj->identity_hash();
+  assert_test_pattern(h_obj, "is_neutral hash=0x");
+}