LockSupport.park之c++源码记录及问题

上层调用java代码

 

park.cpp文件位置，以及os.cpp文件位置。但是我没有找到os类的定义位置，知道的大牛，留言告诉我下。

实现文件位置:

void Parker::park(bool isAbsolute, jlong time) {
  // Optional fast-path check:
  // Return immediately if a permit is available.
  if (_counter > 0) {
      _counter = 0 ;
      OrderAccess::fence();
      return ;
  }

  Thread* thread = Thread::current();
  assert(thread->is_Java_thread(), "Must be JavaThread");
  JavaThread *jt = (JavaThread *)thread;

  // Optional optimization -- avoid state transitions if there's an interrupt pending.
  // Check interrupt before trying to wait
  if (Thread::is_interrupted(thread, false)) {
    return;
  }

  // Next, demultiplex/decode time arguments
  timespec absTime;
  if (time < 0 || (isAbsolute && time == 0) ) { // don't wait at all
    return;
  }
  if (time > 0) {
    unpackTime(&absTime, isAbsolute, time);
  }


  // Enter safepoint region
  // Beware of deadlocks such as 6317397.
  // The per-thread Parker:: mutex is a classic leaf-lock.
  // In particular a thread must never block on the Threads_lock while
  // holding the Parker:: mutex.  If safepoints are pending both the
  // the ThreadBlockInVM() CTOR and DTOR may grab Threads_lock.
  ThreadBlockInVM tbivm(jt);

  // Don't wait if cannot get lock since interference arises from
  // unblocking.  Also. check interrupt before trying wait
  if (Thread::is_interrupted(thread, false) || pthread_mutex_trylock(_mutex) != 0) {
    return;
  }

  int status ;
  if (_counter > 0)  { // no wait needed
    _counter = 0;
    status = pthread_mutex_unlock(_mutex);
    assert (status == 0, "invariant") ;
    OrderAccess::fence();
    return;
  }

#ifdef ASSERT
  // Don't catch signals while blocked; let the running threads have the signals.
  // (This allows a debugger to break into the running thread.)
  sigset_t oldsigs;
  sigset_t* allowdebug_blocked = os::Linux::allowdebug_blocked_signals();
  pthread_sigmask(SIG_BLOCK, allowdebug_blocked, &oldsigs);
#endif

  OSThreadWaitState osts(thread->osthread(), false /* not Object.wait() */);
  jt->set_suspend_equivalent();
  // cleared by handle_special_suspend_equivalent_condition() or java_suspend_self()

  if (time == 0) {
    status = pthread_cond_wait (_cond, _mutex) ;
  } else {
    status = os::Linux::safe_cond_timedwait (_cond, _mutex, &absTime) ;
    if (status != 0 && WorkAroundNPTLTimedWaitHang) {
      pthread_cond_destroy (_cond) ;
      pthread_cond_init    (_cond, NULL);
    }
  }
  assert_status(status == 0 || status == EINTR ||
                status == ETIME || status == ETIMEDOUT,
                status, "cond_timedwait");

#ifdef ASSERT
  pthread_sigmask(SIG_SETMASK, &oldsigs, NULL);
#endif

  _counter = 0 ;
  status = pthread_mutex_unlock(_mutex) ;
  assert_status(status == 0, status, "invariant") ;
  // If externally suspended while waiting, re-suspend
  if (jt->handle_special_suspend_equivalent_condition()) {
    jt->java_suspend_self();
  }

  OrderAccess::fence();
}

这个park代码，有2个地方没有看明白，

 status = os::Linux::safe_cond_timedwait (_cond, _mutex, &absTime) ;

这一行什么意思？没有看到os里面定义Linux，也没有看到os的定义？太菜了。