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



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

I looked at the documentation for the function:

http://msdn.microsoft.com/library/de...eobjectsex.asp

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

--
Bruce Momjian http://candle.pha.pa.us
SRA OSS, Inc. http://www.sraoss.com

+ If your life is a hard drive, Christ can be your backup. +

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"Bruce Momjian" <pgman (AT) candle (DOT) pha.pa.us> wrote
AFAICS, by doing so, the EINTR/EAGAIN will be translated into
WSAINTR/WSAEWOULDBLOCK through *all* the backend code. That's seems not
appropriate for the code not involving any socket stuff ... I think we need
a fix here.

Yeah, looking at other code of using semop(), we could plug in a loop in the
win32 semctl():

/* Quickly lock/unlock the semaphore (if we can) */
+ do
+ {
+ errStatus = semop(semId, &sops, 1);
+ } while (errStatus < 0 && errno == EINTR);

if (semop(semId, &sops, 1) < 0)
return -1;

But:
(1) The EINTR problem happens rather rare, so testing it is difficult;
(2) I would rather not doing the above changes before we understand what's
happened here, especially when we have seen a EAGAIN reported here.

Regards,
Qingqing



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Qingqing Zhou wrote:
Uh, how do we handle it now? I thought we did just that.

OK, so how do we find the answer?

--
Bruce Momjian http://candle.pha.pa.us
SRA OSS, Inc. http://www.sraoss.com

+ If your life is a hard drive, Christ can be your backup. +

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On Tue, 28 Feb 2006, Bruce Momjian wrote:

For both problems, I am uncertain (or I've sent a patch already :-(). Call
more artillery support here ...

Regards,
Qingqing

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Thread added to TODO.detail for Win32:

o Check WSACancelBlockingCall() for interrupts (win32intr)

---------------------------------------------------------------------------

Qingqing Zhou wrote:
--
Bruce Momjian http://candle.pha.pa.us
SRA OSS, Inc. http://www.sraoss.com

+ If your life is a hard drive, Christ can be your backup. +

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