Loop calling CallNamedPipe() several times in case it fails,

since it can be transient failures, causing kill() to not
properly send signals.

Original patch from Steve Marshall, modified by me.

src/port/kill.c

@@ -9,7 +9,7 @@
  *	signals that the backend can recognize.
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/port/kill.c,v 1.11 2009/01/01 17:24:04 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/port/kill.c,v 1.12 2009/02/15 13:58:18 mha Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -25,6 +25,7 @@ pgkill(int pid, int sig)
 	BYTE		sigData = sig;
 	BYTE		sigRet = 0;
 	DWORD		bytes;
+	int			pipe_tries;
 
 	/* we allow signal 0 here, but it will be ignored in pg_queue_signal */
 	if (sig >= PG_SIGNAL_COUNT || sig < 0)
@@ -39,23 +40,33 @@ pgkill(int pid, int sig)
 		return -1;
 	}
 	snprintf(pipename, sizeof(pipename), "\\\\.\\pipe\\pgsignal_%u", pid);
-	if (!CallNamedPipe(pipename, &sigData, 1, &sigRet, 1, &bytes, 1000))
-	{
-		if (GetLastError() == ERROR_FILE_NOT_FOUND)
-			errno = ESRCH;
-		else if (GetLastError() == ERROR_ACCESS_DENIED)
-			errno = EPERM;
-		else
-			errno = EINVAL;
-		return -1;
-	}
-	if (bytes != 1 || sigRet != sig)
+
+	/*
+	 * Writing data to the named pipe can fail for transient reasons.
+	 * Therefore, it is useful to retry if it fails.  The maximum number of
+	 * calls to make was empirically determined from a 90-hour notification
+	 * stress test.
+	 */
+	for (pipe_tries = 0; pipe_tries < 3; pipe_tries++)
 	{
-		errno = ESRCH;
-		return -1;
+		if (CallNamedPipe(pipename, &sigData, 1, &sigRet, 1, &bytes, 1000))
+		{
+			if (bytes != 1 || sigRet != sig)
+			{
+				errno = ESRCH;
+				return -1;
+			}
+			return 0;
+		}
 	}
 
-	return 0;
+	if (GetLastError() == ERROR_FILE_NOT_FOUND)
+		errno = ESRCH;
+	else if (GetLastError() == ERROR_ACCESS_DENIED)
+		errno = EPERM;
+	else
+		errno = EINVAL;
+	return -1;
 }
 
 #endif