[Bug 1201180] Re: Pressing power button turns off the PC ignoring the presence of another session manager

[Iain Lane]

I did some investigation last night. Here's what I found out. gnome-
session doesn't (successfully) set a shutdown inhibitor lock, meaning
that logind shuts the system down as soon as it is asked to. When run,
gnome-session outputs the following warning

  gnome-session[6124]: WARNING: Error getting login monitor: -2

That comes from the following block of code

        if ((ret = sd_login_monitor_new (NULL, &sd_source->monitor)) < 0) {
                g_warning ("Error getting login monitor: %d", ret);
        } else {
                sd_source->pollfd.fd = sd_login_monitor_get_fd (sd_source->monitor);
                sd_source->pollfd.events = G_IO_IN;
                g_source_add_poll (source, &sd_source->pollfd);
        }

The return code there is '-2' which corresponds to ENOENT.

Checking the code for sd_login_monitor_new() in systemd shows that this
function tries to inotify_add_watch() on a number of paths systemd cares
about. If we strace -f -e trace=inotify_add_watch gnome-session then the
output shows

  [pid  5439] inotify_add_watch(14, "/sys/fs/cgroup/systemd/machine",
IN_MOVED_TO|IN_CREATE|IN_DELETE) = -1 ENOENT (No such file or directory)

And indeed this directory has not been created. In
systemd:src/core/cgroup.c, these hierarchies are created here:

        if (m->running_as == SYSTEMD_SYSTEM) {
                cg_create(SYSTEMD_CGROUP_CONTROLLER, m->cgroup_hierarchy, "../user");
                cg_create(SYSTEMD_CGROUP_CONTROLLER, m->cgroup_hierarchy, "../machine");
        }

I believe the if check there is essentially systemd as PID 1, i.e. not
true for Ubuntu.

In systemd git this seems to have moved to /run/systemd/machines/
created by systemd-machined.

Now, I'm not totally sure that this broken call is why the inhibitor
lock isn't being set, but sd_login_monitor_new() definitely shouldn't be
broken anyway and fixing this seems like a good place to start.

** Also affects: systemd (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1201180

Title:
  Pressing power button turns off the PC ignoring the presence of
  another session manager

Status in “gnome-session” package in Ubuntu:
  New
Status in “systemd” package in Ubuntu:
  New
Status in “systemd-shim” package in Ubuntu:
  Invalid

Bug description:
  In saucy the PC powers down as soon as I press the power button, it
  seems that systemd is calling "poweroff", but I'm not sure if it's
  doing that in response of some other event (i.e. as callback of a dbus
  call):

  root      4998  0.0  0.0 177932  2104 ?        Sl   20:41   0:00 /usr/lib/x86_64-linux-gnu/systemd-shim
  root      5012  0.0  0.0   4440   624 ?        S    20:41   0:00  \_ sh -c /sbin/poweroff
  root      5013  0.0  0.0   4440   628 ?        S    20:41   0:00      \_ /bin/sh /sbin/shutdown -h -P now

  In any case the caller or systemd itself should be aware that there's
  a session-manager running and that it shouldn't actually directly
  power off the system then.

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