Re: Latch implementation that wakes on postmaster death on both win32 and Unix

From: Peter Geoghegan <peter(at)2ndquadrant(dot)com>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: PG Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Latch implementation that wakes on postmaster death on both win32 and Unix
Date: 2011-06-16 12:07:17
Message-ID: BANLkTimi_CgmEV-XQviTAtPb=v16=XkGAQ@mail.gmail.com
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I had another quick look-over this patch, and realised that I made a
minor mistake:

+void
+ReleasePostmasterDeathWatchHandle(void)
+{
+ /* MyProcPid won't have been set yet */
+ Assert(PostmasterPid != getpid());
+ /* Please don't ask twice */
+ Assert(postmaster_alive_fds[POSTMASTER_FD_OWN] != -1);
+ /* Release parent's ownership fd - only postmaster should hold it */
+ if (close(postmaster_alive_fds[ POSTMASTER_FD_OWN]))
+ {
+ ereport(FATAL,
+ (errcode_for_socket_access(),
+ errmsg("Failed to close file descriptor associated with
Postmaster death in child process %d", MyProcPid)));
+ }
+ postmaster_alive_fds[POSTMASTER_FD_OWN] = -1;
+}
+

MyProcPid is used in this errmsg, and as noted in the first comment,
it isn't expected to be initialised when
ReleasePostmasterDeathWatchHandle() is called. Therefore, MyProcPid
should be replaced with a call to getpid(), just as it is for
Assert(PostmasterPid != getpid()).

I suppose that you could take the view that MyProcPid ought to be
initialised before the function is called, but I thought this was the
least worst way. Better to do it this way than to touch all the
different ways in which MyProcPid might be initialised, I suspect.

--
Peter Geoghegan       http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training and Services

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