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Fix infinite sleep and failes of send in Win32.

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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
This commit is contained in:
Teodor Sigaev 2006-10-13 13:59:47 +00:00
parent efa0e8639f
commit 47df6e7e2d
1 changed files with 81 additions and 25 deletions
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106
src/backend/port/win32/socket.c
View File

@ -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;
/*
* 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 (r == SOCKET_ERROR &&
WSAGetLastError() != WSAEWOULDBLOCK)
{
TranslateSocketError();
return -1;
}
/* No error, zero bytes (win2000+) or error+WSAEWOULDBLOCK (<=nt4) */
if (pgwin32_waitforsinglesocket(s, FD_WRITE | FD_CLOSE) == 0)
return -1;
}
/* No error, zero bytes (win2000+) or error+WSAEWOULDBLOCK (<=nt4) */
if (pgwin32_waitforsinglesocket(s, FD_WRITE | FD_CLOSE) == 0)
return -1;
r = WSASend(s, &wbuf, 1, &b, flags, NULL, NULL);
if (r == SOCKET_ERROR)
{
TranslateSocketError();
return -1;
}
return b;
return -1;
}