From 51e8e187d1ca6963a5467890a7f8ebbf8b59f573 Mon Sep 17 00:00:00 2001
From: "Marc G. Fournier" <scrappy@hub.org>
Date: Tue, 25 Aug 1998 21:32:10 +0000
Subject: [PATCH] Massimo Dal Zotto <dz@cs.unitn.it>
> socket-flock.patch
>
> use advisory locks to check if the unix socket can be deleted.
> A running postmaster keeps a lock on that file. A starting
> postmaster exits if the file exists and is locked, otherwise
> it deletes the sockets and proceeds.
> This avoid the need to remove manually the file after a postmaster
> or system crash.
> I don't know if flock is available on any system. If not we could
> define a HAVE_FLOCK set by configure.
---
src/backend/libpq/pqcomm.c | 39 ++++++++++++++++++++++++++++++++++----
1 file changed, 35 insertions(+), 4 deletions(-)
diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
index 56f0fd658e9..1a67903959d 100644
--- a/src/backend/libpq/pqcomm.c
+++ b/src/backend/libpq/pqcomm.c
@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/libpq/pqcomm.c,v 1.50 1998/07/26 04:30:28 scrappy Exp $
+ * $Header: /cvsroot/pgsql/src/backend/libpq/pqcomm.c,v 1.51 1998/08/25 21:32:10 scrappy Exp $
*
*-------------------------------------------------------------------------
*/
@@ -55,6 +55,7 @@
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
+#include <sys/file.h>
#if defined(linux)
#ifndef SOMAXCONN
@@ -70,6 +71,7 @@
#ifdef MULTIBYTE
#include "mb/pg_wchar.h"
#endif
+#include "utils/trace.h"
/* ----------------
* declarations
@@ -522,6 +524,7 @@ StreamServerPort(char *hostName, short portName, int *fdP)
family;
size_t len;
int one = 1;
+ int lock_fd;
family = ((hostName != NULL) ? AF_INET : AF_UNIX);
@@ -550,6 +553,20 @@ StreamServerPort(char *hostName, short portName, int *fdP)
{
len = UNIXSOCK_PATH(saddr.un, portName);
strcpy(sock_path, saddr.un.sun_path);
+
+ /*
+ * If the socket exists but nobody has an advisory lock on it
+ * we can safely delete the file.
+ */
+ if ((lock_fd = open(sock_path, O_RDONLY|O_NONBLOCK, 0666)) >= 0) {
+ if (flock(lock_fd, LOCK_EX|LOCK_NB) == 0) {
+ TPRINTF(TRACE_VERBOSE, "flock on %s, deleting", sock_path);
+ unlink(sock_path);
+ } else {
+ TPRINTF(TRACE_VERBOSE, "flock failed for %s", sock_path);
+ }
+ close(lock_fd);
+ }
}
else
{
@@ -564,18 +581,32 @@ StreamServerPort(char *hostName, short portName, int *fdP)
"FATAL: StreamServerPort: bind() failed: errno=%d\n",
errno);
pqdebug("%s", PQerrormsg);
- strcat(PQerrormsg, "\tIs another postmaster already running on that port?\n");
+ strcat(PQerrormsg,
+ "\tIs another postmaster already running on that port?\n");
if (family == AF_UNIX)
- strcat(PQerrormsg, "\tIf not, remove socket node (/tmp/.s.PGSQL.<portnumber>)and retry.\n");
+ sprintf(PQerrormsg+strlen(PQerrormsg),
+ "\tIf not, remove socket node (%s) and retry.\n",
+ sock_path);
else
strcat(PQerrormsg, "\tIf not, wait a few seconds and retry.\n");
fputs(PQerrormsg, stderr);
return (STATUS_ERROR);
}
- if (family == AF_UNIX)
+ if (family == AF_UNIX) {
on_proc_exit(StreamDoUnlink, NULL);
+ /*
+ * Open the socket file and get an advisory lock on it.
+ * The lock_fd is left open to keep the lock.
+ */
+ if ((lock_fd = open(sock_path, O_RDONLY|O_NONBLOCK, 0666)) >= 0) {
+ if (flock(lock_fd, LOCK_EX|LOCK_NB) != 0) {
+ TPRINTF(TRACE_VERBOSE, "flock error for %s", sock_path);
+ }
+ }
+ }
+
listen(fd, SOMAXCONN);
/*
--
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