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

Qingqing Zhou wrote:
> 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?

We did this so that our code could refer to EINTR/EAGAIN without
port-specific tests.

> (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?

I looked at the documentation for the function:

    http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/base/waitformultipleobjectsex.asp

and it isn't clear what return failure values it has.  We certainly
could loop on WSAEINTR.  Can you test it?

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