FATAL: semctl(1672698088, 12, SETVAL, 0) failed

I encountered an error when I fast shutdown 8.1.1 on Win2k:

    FATAL:  semctl(1672698088, 12, SETVAL, 0) failed:  A blocking operation
    was interrupted by a call to WSACancelBlockingCall.

A similar error on 8.1/win2003 was reported on pgsql-general (sorry, I can't
dig out the
original post from our web archives):

    From:  Niederland
    Date:  Tues, Dec 13 2005 9:49 am

    2005-12-12 20:30:00 FATAL:  semctl(50884184, 15, SETVAL, 0) failed: A
    non-blocking socket operation could not be completed immediately.

---

There are two problems here:

(1) Why a socket error?
In port/win32.h, we have

#undef EAGAIN
#undef EINTR
#define EINTR WSAEINTR
#define EAGAIN WSAEWOULDBLOCK

What's the rationale of doing so?

(2) What's happened here?
It may come from PGSemaphoreReset(), and win32 semop() looks like this:

  ret = WaitForMultipleObjectsEx(2, wh, FALSE, (sops[0].sem_flg &
IPC_NOWAIT) ? 0 : INFINITE, TRUE);
  ...
  else if (ret == WAIT_OBJECT_0 + 1 || ret == WAIT_IO_COMPLETION)
  {
   pgwin32_dispatch_queued_signals();
   errno = EINTR;
  }
  else if (ret == WAIT_TIMEOUT)
   errno = EAGAIN;

So it seems the EINTR is caused by an incoming signal, the EAGAIN is caused
by a TIMEOUT ... any ideas?

Regards,
Qingqing