В Fri, 17 Apr 2015 14:04:18 -0600 Daniel Drake <dr...@endlessm.com> пишет:
> Hi, > > I'm investigating why "systemctl stop gdm; Xorg" usually fails. The > new X process complains that X is still running. > > Here's what I think is happening: > > 1. systemd sends SIGTERM to gdm to stop the service > > 2. gdm exits - it has a simple SIGTERM handler which just quits the > mainloop without doing any cleanup (as far as I can see, it doesn't > make any attempt to kill the child X server) > > 3. X exits because of PR_SET_PDEATHSIG (i.e. it's set to be > automatically killed when the parent goes away). The killed process > enters defunct state and is reparented to PID 1, presumably also > moving it out of the gdm cgroup. > No, it remains in cgroup. Otherwise systemd service management would not be possible at all ... > 4. systemd notes that gdm's cgroup is empty and decides that gdm is > now successfully stopped. > I looked at display-manager.service here and it sets KillMode=process. That is better explanation to your observation. > 5. systemctl returns and now Xorg is launched immediately. Xorg reads > the PID of the old Xorg process from /tmp, and notices that that PID > is still in use (it is still an unreaped zombie) because kill() > doesn't return an error. Xorg aborts thinking that it is already > running. > > 6. Moments later, systemd reaps the zombie. Oops, too late. > > > Does that make sense? > I wonder how it is best to fix this. Is it a bug that systemd decided > that gdm.service had stopped before it had reaped zombie processes > that originally belonged to gdm? > > Is it a gdm bug that killing gdm doesn't make any attempt to reap X > before going away itself? (they chose PR_SET_PDEATHSIG to do something > similar, but maybe we have to argue that it is not quite sufficient) > > Thanks > Daniel > _______________________________________________ > systemd-devel mailing list > systemd-devel@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/systemd-devel _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
