// rmonitor - pre-checked for validity

jvmtiError
JvmtiEnv::RawMonitorEnter(JvmtiRawMonitor * rmonitor) {

  {- -------------------------------------------
  (1) (以下の処理は, HotSpot の起動中(= Threads::number_of_threads() が 0)かどうかで ２通りに分かれる)
      ---------------------------------------- -}

  {- -------------------------------------------
  (1) (以下は HotSpot の起動中(= Threads::number_of_threads() が 0)の場合)
      (この段階では JavaThreads オブジェクトが作れていないので ObjectMonitor も使えない)
      ---------------------------------------- -}

      if (Threads::number_of_threads() == 0) {

    {- -------------------------------------------
  (1.1) JvmtiPendingMonitors::enter() を呼んで, JvmtiPendingMonitors 内の pending list に追加する.
        ---------------------------------------- -}

        // No JavaThreads exist so ObjectMonitor enter cannot be
        // used, add this raw monitor to the pending list.
        // The pending monitors will be actually entered when
        // the VM is setup.
        // See transition_pending_raw_monitors in create_vm()
        // in thread.cpp.
        JvmtiPendingMonitors::enter(rmonitor);

  {- -------------------------------------------
  (1) (以下は HotSpot の起動完了後の場合)
      (この場合の処理は, カレントスレッドが JavaThread かそれ以外(VMThread or ConcurrentGCThread)かで2通りに分かれる)
      ---------------------------------------- -}

      } else {

    {- -------------------------------------------
  (1.1) (変数宣言など)
        ---------------------------------------- -}

        int r;
        Thread* thread = Thread::current();

    {- -------------------------------------------
  (1.1) (以下は, カレントスレッドが JavaThread の場合)
        ---------------------------------------- -}

        if (thread->is_Java_thread()) {

      {- -------------------------------------------
  (1.1.1) (変数宣言など)
          ---------------------------------------- -}

          JavaThread* current_thread = (JavaThread*)thread;

      {- -------------------------------------------
  (1.1.1) JvmtiRawMonitor::raw_enter() を呼んでロックを取得する.

          (なんだか JavaThreadState の変更処理で手こずっているようだが... #TODO)
          ---------------------------------------- -}

    #ifdef PROPER_TRANSITIONS
          // Not really unknown but ThreadInVMfromNative does more than we want
          ThreadInVMfromUnknown __tiv;
          {
            ThreadBlockInVM __tbivm(current_thread);
            r = rmonitor->raw_enter(current_thread);
          }
    #else
          /* Transition to thread_blocked without entering vm state          */
          /* This is really evil. Normally you can't undo _thread_blocked    */
          /* transitions like this because it would cause us to miss a       */
          /* safepoint but since the thread was already in _thread_in_native */
          /* the thread is not leaving a safepoint safe state and it will    */
          /* block when it tries to return from native. We can't safepoint   */
          /* block in here because we could deadlock the vmthread. Blech.    */

          JavaThreadState state = current_thread->thread_state();
          assert(state == _thread_in_native, "Must be _thread_in_native");
          // frame should already be walkable since we are in native
          assert(!current_thread->has_last_Java_frame() ||
                 current_thread->frame_anchor()->walkable(), "Must be walkable");
          current_thread->set_thread_state(_thread_blocked);

          r = rmonitor->raw_enter(current_thread);
          // restore state, still at a safepoint safe state
          current_thread->set_thread_state(state);

    #endif /* PROPER_TRANSITIONS */

      {- -------------------------------------------
  (1.1.1) (assert)
          ---------------------------------------- -}

          assert(r == ObjectMonitor::OM_OK, "raw_enter should have worked");

    {- -------------------------------------------
  (1.1) (以下は, カレントスレッドが VMThread or ConcurrentGCThread の場合)
        ---------------------------------------- -}

        } else {

      {- -------------------------------------------
  (1.1.1) JvmtiRawMonitor::raw_enter() を呼んでロックを取得する.
          ---------------------------------------- -}

          if (thread->is_VM_thread() || thread->is_ConcurrentGC_thread()) {
            r = rmonitor->raw_enter(thread);
          } else {
            ShouldNotReachHere();
          }
        }

    {- -------------------------------------------
  (1.1) もし JvmtiRawMonitor::raw_enter() が失敗していたら, JVMTI_ERROR_INTERNAL をリターン. (このパスはあり得なさそうだが...)
        ---------------------------------------- -}

        if (r != ObjectMonitor::OM_OK) {  // robustness
          return JVMTI_ERROR_INTERNAL;
        }
      }

  {- -------------------------------------------
  (1) リターン
      ---------------------------------------- -}

      return JVMTI_ERROR_NONE;
    } /* end RawMonitorEnter */