Re: Back-patch use of unnamed POSIX semaphores for Linux?

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Wed, Dec 7, 2016 at 6:49 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> This still doesn't address the real question, which is whether RemoveIPC
>> does anything if KillUserProcesses is off, and whether that behavior
>> has changed. I don't see anything about RemoveIPC in that thread.

> http://www.dsm.fordham.edu/cgi-bin/man-cgi.pl?topic=logind.conf&ampsect=5
> suggests that KillUserProcesses and RemoveIPC are separate cleanup
> behaviors triggered by the same underlying cause (termination of last
> session).

Yeah, I read that man page too, but ...

The test case I was using was to ssh into the box, launch a
postmaster using the old-school "nohup postmaster &" technique, and
log out. What I saw was that the "/usr/lib/systemd/systemd --user"
process Alex referred to would be launched when the ssh connection
started, and would stick around as long as the postmaster was there,
if KillUserProcesses was off. (If it was on, something SIGTERM'd
the postmaster as soon as I disconnected.) So if they really are
independent behaviors, I'd have expected the same something to have
killed the semaphores as soon as I disconnected; but that did NOT
happen.

[ Yes, RemoveIPC is definitely on: I turned it on explicitly in
logind.conf, just in case the comment claiming it's on by default
is a lie. ]

BTW, I also tried this from the console, but the results were confused
by the fact that GNOME seems to launch approximately a metric buttload
of "helper" processes, which don't disappear when I log out. If that's
the behavior Lennart is trying to get rid of, I can see his point; but
I tend to agree with the other comments in that thread that this should
be fixed in GNOME not by breaking longstanding working assumptions.

When I get a chance, I think I'll try F24 and see if it behaved
differently. F23 might be interesting too if it's still downloadable.

regards, tom lane