Index: src/backend/utils/init/miscinit.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/init/miscinit.c,v
retrieving revision 1.176
diff -c -r1.176 miscinit.c
*** src/backend/utils/init/miscinit.c	12 Aug 2009 20:53:30 -0000	1.176
--- src/backend/utils/init/miscinit.c	26 Aug 2009 23:24:56 -0000
***************
*** 683,689 ****
  	int			len;
  	int			encoded_pid;
  	pid_t		other_pid;
! 	pid_t		my_pid = getpid();
  
  	/*
  	 * We need a loop here because of race conditions.	But don't loop forever
--- 683,728 ----
  	int			len;
  	int			encoded_pid;
  	pid_t		other_pid;
! 	pid_t		my_pid,
! 				my_p_pid,
! 				my_gp_pid;
! 	const char *envvar;
! 
! 	/*
! 	 * If the PID in the lockfile is our own PID or our parent's or
! 	 * grandparent's PID, then the file must be stale (probably left over from
! 	 * a previous system boot cycle).  We need to check this because of the
! 	 * likelihood that a reboot will assign exactly the same PID as we had in
! 	 * the previous reboot, or one that's only one or two counts larger and
! 	 * hence the lockfile's PID now refers to an ancestor shell process.  We
! 	 * allow pg_ctl to pass down its parent shell PID (our grandparent PID)
! 	 * via the environment variable PG_GRANDPARENT_PID; this is so that
! 	 * launching the postmaster via pg_ctl can be just as reliable as
! 	 * launching it directly.  There is no provision for detecting
! 	 * further-removed ancestor processes, but if the init script is written
! 	 * carefully then all but the immediate parent shell will be root-owned
! 	 * processes and so the kill test will fail with EPERM.  Note that we
! 	 * cannot get a false negative this way, because an existing postmaster
! 	 * would surely never launch a competing postmaster or pg_ctl process
! 	 * directly.
! 	 */
! 	my_pid = getpid();
! 
! #ifndef WIN32
! 	my_p_pid = getppid();
! #else
! 	/*
! 	 * Windows hasn't got getppid(), but doesn't need it since it's not
! 	 * using real kill() either...
! 	 */
! 	my_p_pid = 0;
! #endif
! 
! 	envvar = getenv("PG_GRANDPARENT_PID");
! 	if (envvar)
! 		my_gp_pid = atoi(envvar);
! 	else
! 		my_gp_pid = 0;
  
  	/*
  	 * We need a loop here because of race conditions.	But don't loop forever
***************
*** 745,761 ****
  		/*
  		 * Check to see if the other process still exists
  		 *
! 		 * If the PID in the lockfile is our own PID or our parent's PID, then
! 		 * the file must be stale (probably left over from a previous system
! 		 * boot cycle).  We need this test because of the likelihood that a
! 		 * reboot will assign exactly the same PID as we had in the previous
! 		 * reboot.	Also, if there is just one more process launch in this
! 		 * reboot than in the previous one, the lockfile might mention our
! 		 * parent's PID.  We can reject that since we'd never be launched
! 		 * directly by a competing postmaster.	We can't detect grandparent
! 		 * processes unfortunately, but if the init script is written
! 		 * carefully then all but the immediate parent shell will be
! 		 * root-owned processes and so the kill test will fail with EPERM.
  		 *
  		 * We can treat the EPERM-error case as okay because that error
  		 * implies that the existing process has a different userid than we
--- 784,794 ----
  		/*
  		 * Check to see if the other process still exists
  		 *
! 		 * Per discussion above, my_pid, my_p_pid, and my_gp_pid can be
! 		 * ignored as false matches.
! 		 *
! 		 * Normally kill() will fail with ESRCH if the given PID doesn't
! 		 * exist.
  		 *
  		 * We can treat the EPERM-error case as okay because that error
  		 * implies that the existing process has a different userid than we
***************
*** 772,789 ****
  		 * Unix socket file belonging to an instance of Postgres being run by
  		 * someone else, at least on machines where /tmp hasn't got a
  		 * stickybit.)
- 		 *
- 		 * Windows hasn't got getppid(), but doesn't need it since it's not
- 		 * using real kill() either...
- 		 *
- 		 * Normally kill() will fail with ESRCH if the given PID doesn't
- 		 * exist.
  		 */
! 		if (other_pid != my_pid
! #ifndef WIN32
! 			&& other_pid != getppid()
! #endif
! 			)
  		{
  			if (kill(other_pid, 0) == 0 ||
  				(errno != ESRCH && errno != EPERM))
--- 805,813 ----
  		 * Unix socket file belonging to an instance of Postgres being run by
  		 * someone else, at least on machines where /tmp hasn't got a
  		 * stickybit.)
  		 */
! 		if (other_pid != my_pid && other_pid != my_p_pid &&
! 			other_pid != my_gp_pid)
  		{
  			if (kill(other_pid, 0) == 0 ||
  				(errno != ESRCH && errno != EPERM))
Index: src/bin/pg_ctl/pg_ctl.c
===================================================================
RCS file: /cvsroot/pgsql/src/bin/pg_ctl/pg_ctl.c,v
retrieving revision 1.111
diff -c -r1.111 pg_ctl.c
*** src/bin/pg_ctl/pg_ctl.c	11 Jun 2009 14:49:07 -0000	1.111
--- src/bin/pg_ctl/pg_ctl.c	26 Aug 2009 23:24:56 -0000
***************
*** 672,677 ****
--- 672,692 ----
  		unlimit_core_size();
  #endif
  
+ 	/*
+ 	 * If possible, tell the postmaster our parent shell's PID (see the
+ 	 * comments in CreateLockFile() for motivation).  Windows hasn't got
+ 	 * getppid() unfortunately.
+ 	 */
+ #ifndef WIN32
+ 	{
+ 		static char env_var[32];
+ 
+ 		snprintf(env_var, sizeof(env_var), "PG_GRANDPARENT_PID=%d",
+ 				 (int) getppid());
+ 		putenv(env_var);
+ 	}
+ #endif
+ 
  	exitcode = start_postmaster();
  	if (exitcode != 0)
  	{