JVM Mutex Monitor::lock

void Monitor::lock (Thread * Self) {

#ifdef CHECK_UNHANDLED_OOPS

  // Clear unhandled oops so we get a crash right away.  Only clear for non-vm

  // or GC threads.

  if (Self->is_Java_thread()) {

    Self->clear_unhandled_oops();

  }

#endif // CHECK_UNHANDLED_OOPS

  debug_only(check_prelock_state(Self));

  assert (_owner != Self              , "invariant") ;

  assert (_OnDeck != Self->_MutexEvent, "invariant") ;

  if (TryFast()) {

 Exeunt:

    assert (ILocked(), "invariant") ;

    assert (owner() == NULL, "invariant");

    set_owner (Self);

    return ;

  }

  // The lock is contended ...

  bool can_sneak = Self->is_VM_thread() && SafepointSynchronize::is_at_safepoint();

  if (can_sneak && _owner == NULL) {

    // a java thread has locked the lock but has not entered the

    // critical region -- let's just pretend we've locked the lock

    // and go on.  we note this with _snuck so we can also

    // pretend to unlock when the time comes.

    _snuck = true;

    goto Exeunt ;

  }

  // Try a brief spin to avoid passing thru thread state transition ...

  if (TrySpin (Self)) goto Exeunt ;

  check_block_state(Self);

  if (Self->is_Java_thread()) {

    // Horribile dictu - we suffer through a state transition

    assert(rank() > Mutex::special, "Potential deadlock with special or lesser rank mutex");

    ThreadBlockInVM tbivm ((JavaThread *) Self) ;

    ILock (Self) ;

  } else {

    // Mirabile dictu

    ILock (Self) ;

  }

  goto Exeunt ;

}