[systemd-bugs] [Bug 88381] Logging out in VT freezes display + input

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88381

--- Comment #4 from Lennart Poettering <lennart at poettering.net> ---
(In reply to amosonn from comment #3)
> System does not seem to react to keypresses, at least not as far as display
> is concerned; I will check more thoroughly whether keypresses still go
> through to the X session, and only display is cut off; however, I think this
> is not the case.
> 
> As far as I understand, systemd is, at least in part, responsible for
> managing session switches, incl. VT switches. Therefore, since the system
> still runs (audio output from online streaming continues normally), I assume
> that systemd somehow denies the X session of access to the display and
> keyboard, but still intercepts keypresses so a switch to another VT is also
> impossible.

logind subscribes to VT chnages, and can issue them. But VT change keypress are
handled by your display server or by the kernel, logind is not involved.

> As I have mentioned, sshd does not completely hang; it does respond to a
> connection, but fails to open a new session (at least as far as can be
> inferred from the output on the remote host). As journald logs stop after
> the fatal logout, I can't tell for sure what happens.

This feels like a kernel hang of some kind, as userspace appears to be stuck
entirely.

Note that pam_systemd on most distros is included in the PAM stack as
non-fatal. Thus, whatever happens, if logind is stuck, you can still log in.
Given that you cannot login this is likely caused by something else, not
logind.

> Lastly, this might be related to some issue with getty. However, even in the
> case where getty hangs, I'd expect systemd to eventually "forcefully"
> rescind access to display and keyboard and transfer it to the requested VT
> (that of the X session).

Well, if the entire userspace is dead (which appears to be the case), then
logind is dead too.

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