From 47df6e7e2d754c6330e85d247987352f0a25e60a Mon Sep 17 00:00:00 2001
From: Teodor Sigaev <teodor@sigaev.ru>
Date: Fri, 13 Oct 2006 13:59:47 +0000
Subject: [PATCH] Fix infinite sleep and failes of send in Win32.
1) pgwin32_waitforsinglesocket(): WaitForMultipleObjectsEx now called with
finite timeout (100ms) in case of FP_WRITE and UDP socket. If timeout occurs
then pgwin32_waitforsinglesocket() tries to write empty packet goes to
WaitForMultipleObjectsEx again.
2) pgwin32_send(): add loop around WSASend and pgwin32_waitforsinglesocket().
The reason is: for overlapped socket, 'ok' result from
pgwin32_waitforsinglesocket() isn't guarantee that socket is still free,
it can become busy again and following WSASend call will fail with
WSAEWOULDBLOCK error.
See http://archives.postgresql.org/pgsql-hackers/2006-10/msg00561.php
---
src/backend/port/win32/socket.c | 106 ++++++++++++++++++++++++--------
1 file changed, 81 insertions(+), 25 deletions(-)
diff --git a/src/backend/port/win32/socket.c b/src/backend/port/win32/socket.c
index 47bb0d9cb85..6489c64daee 100644
--- a/src/backend/port/win32/socket.c
+++ b/src/backend/port/win32/socket.c
@@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/port/win32/socket.c,v 1.13 2006/10/04 00:29:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/port/win32/socket.c,v 1.14 2006/10/13 13:59:47 teodor Exp $
*
*-------------------------------------------------------------------------
*/
@@ -102,11 +102,23 @@ pgwin32_poll_signals(void)
return 0;
}
+static int
+isDataGram(SOCKET s) {
+ int type;
+ int typelen = sizeof(type);
+
+ if ( getsockopt(s, SOL_SOCKET, SO_TYPE, (char*)&type, &typelen) )
+ return 1;
+
+ return ( type == SOCK_DGRAM ) ? 1 : 0;
+}
+
int
pgwin32_waitforsinglesocket(SOCKET s, int what)
{
static HANDLE waitevent = INVALID_HANDLE_VALUE;
static SOCKET current_socket = -1;
+ static int isUDP = 0;
HANDLE events[2];
int r;
@@ -127,8 +139,12 @@ pgwin32_waitforsinglesocket(SOCKET s, int what)
* socket from a previous call
*/
- if (current_socket != s && current_socket != -1)
- WSAEventSelect(current_socket, waitevent, 0);
+ if (current_socket != s)
+ {
+ if ( current_socket != -1 )
+ WSAEventSelect(current_socket, waitevent, 0);
+ isUDP = isDataGram(s);
+ }
current_socket = s;
@@ -140,7 +156,46 @@ pgwin32_waitforsinglesocket(SOCKET s, int what)
events[0] = pgwin32_signal_event;
events[1] = waitevent;
- r = WaitForMultipleObjectsEx(2, events, FALSE, INFINITE, TRUE);
+
+ /*
+ * Just a workaround of unknown locking problem with writing
+ * in UDP socket under high load:
+ * Client's pgsql backend sleeps infinitely in
+ * WaitForMultipleObjectsEx, pgstat process sleeps in
+ * pgwin32_select(). So, we will wait with small
+ * timeout(0.1 sec) and if sockect is still blocked,
+ * try WSASend (see comments in pgwin32_select) and wait again.
+ */
+ if ((what & FD_WRITE) && isUDP)
+ {
+ for(;;)
+ {
+ r = WaitForMultipleObjectsEx(2, events, FALSE, 100, TRUE);
+
+ if ( r == WAIT_TIMEOUT )
+ {
+ char c;
+ WSABUF buf;
+ DWORD sent;
+
+ buf.buf = &c;
+ buf.len = 0;
+
+ r = WSASend(s, &buf, 1, &sent, 0, NULL, NULL);
+ if (r == 0) /* Completed - means things are fine! */
+ return 1;
+ else if ( WSAGetLastError() != WSAEWOULDBLOCK )
+ {
+ TranslateSocketError();
+ return 0;
+ }
+ }
+ else
+ break;
+ }
+ }
+ else
+ r = WaitForMultipleObjectsEx(2, events, FALSE, INFINITE, TRUE);
if (r == WAIT_OBJECT_0 || r == WAIT_IO_COMPLETION)
{
@@ -280,30 +335,31 @@ pgwin32_send(SOCKET s, char *buf, int len, int flags)
wbuf.len = len;
wbuf.buf = buf;
- r = WSASend(s, &wbuf, 1, &b, flags, NULL, NULL);
- if (r != SOCKET_ERROR && b > 0)
- /* Write succeeded right away */
- return b;
-
- if (r == SOCKET_ERROR &&
- WSAGetLastError() != WSAEWOULDBLOCK)
- {
- TranslateSocketError();
- return -1;
- }
-
- /* No error, zero bytes (win2000+) or error+WSAEWOULDBLOCK (<=nt4) */
+ /*
+ * Readiness of socket to send data to UDP socket
+ * may be not true: socket can become busy again! So loop
+ * until send or error occurs.
+ */
+ for(;;) {
+ r = WSASend(s, &wbuf, 1, &b, flags, NULL, NULL);
+ if (r != SOCKET_ERROR && b > 0)
+ /* Write succeeded right away */
+ return b;
+
+ if (r == SOCKET_ERROR &&
+ WSAGetLastError() != WSAEWOULDBLOCK)
+ {
+ TranslateSocketError();
+ return -1;
+ }
- if (pgwin32_waitforsinglesocket(s, FD_WRITE | FD_CLOSE) == 0)
- return -1;
+ /* No error, zero bytes (win2000+) or error+WSAEWOULDBLOCK (<=nt4) */
- r = WSASend(s, &wbuf, 1, &b, flags, NULL, NULL);
- if (r == SOCKET_ERROR)
- {
- TranslateSocketError();
- return -1;
+ if (pgwin32_waitforsinglesocket(s, FD_WRITE | FD_CLOSE) == 0)
+ return -1;
}
- return b;
+
+ return -1;
}
--
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