GLib 2.73.2+: Terminal freezes when closing with the close button

[bobby285271]

GLib 2.73.2+: Terminal freezes when closing with the close button

[jeremypw]

In most cases the user will "Force Quit" anyway so there seems little harm in doing it code?

[jeremypw]

So the issue is that the tab cannot be closed with the close button if the child is a zombie? Do you know why the child became zombified? Is there a way of detecting a zombie in code?

[bobby285271]

I actually don't know why it becomes a zombie :-(

[jeremypw]

If the cause is external to Terminal/Elementary, then throwing that dialog with a Force Quit option seems a reasonable response pro temp pending an upstream fix. Otherwise we need to stop the zombification.

[bobby285271]

😞 Yeah I am still looking into it, it seems that it only becomes a zombie when the first Posix.kill (this.child_pid, Posix.Signal.HUP); happened and it was not zombie before. Actually this is what I did:

public void term_ps () {
    killed = true;

    warning (this.child_pid.to_string ());
    Thread.usleep (10000000);
    Posix.kill (this.child_pid, Posix.Signal.HUP);
    // Posix.kill (this.child_pid, Posix.Signal.TERM);
    warning ("Done");
    while (true) { }
}

Do you have any suggestions on how to debug this? I actually tried launching a random zenity process (outside of the elementary terminal), get the pid and replace this.child_pid with it like:

public void term_ps () {
    killed = true;

    // warning (this.child_pid.to_string ());
    Thread.usleep (10000000);
    Posix.kill (145200, Posix.Signal.HUP);
    // Posix.kill (this.child_pid, Posix.Signal.TERM);
    warning ("Done");
    while (true) { }
}

While the terminal still freeze (as expected) Posix.kill actually successfully hang up the zenity process.

Update: Also tried using a pid from a zsh which is launched in a xterm terminal, with the same steps Posix.kill is still able to hang up the external zsh.

[jeremypw]

I'll have a look into it and see if I can reproduce. Perhaps we should not be able to close a tab with running child anyway? What becomes of a the child process if Terminal is terminated some other way?

[jeremypw]

What setting save-exited-tabs do you have? If this is true then the shell process for closed tabs will continue until the Terminal window is closed and when that tab is restored no new shell process is created. The default setting on Elementary is true.

[jeremypw]

I have switch my default shell to zsh but as yet not reproduced the freeze.

[jeremypw]

Can you reproduce this on NixOS using bash as the shell?

[jeremypw]

Can you reproduce this on NixOS using bash as the shell?

[bobby285271]

gsettings get io.elementary.terminal.settings save-exited-tabs gave me true. Yeah it can be possible that those GNOME 43 packages are needed to reproduce the issue :-(

[bobby285271]

Can you reproduce this on NixOS using bash as the shell?

Yes (actually my laptop is using zsh but the screenshot above is a VM that uses bash)

[jeremypw]

Unfortunately the commit that introduced this possibility of an infinite loop by removing the maximum number of tries to kill the shell process is too old for me to find out what issue this was supposed to fix. It would seem sensible to impose a maximum number of retries.

[jeremypw]

Just tried commenting out the while of that loop so Terminal no longer tries to close the shell process. The processes and any child processes get closed anyway so 🤷

[bobby285271]

Can https://gitlab.gnome.org/GNOME/glib/-/merge_requests/2408 be the reason of this issue? I actually did some bisect and noticed that MR.

/cc @jtojnar

[bobby285271]

Hmmm... So maybe this will be another possible workaround?

public void term_ps () {
    killed = true;

    Posix.kill (this.child_pid, Posix.Signal.HUP);
    Posix.kill (this.child_pid, Posix.Signal.TERM);

    int status;
    Posix.waitpid (this.child_pid, out status, 0);
}

From my testing the terminal will no longer freeze when closing but you will get a new warning (when closing the terminal) if you build it with GLib 2.72.3

[GLib] GChildWatchSource: Exit status of a child process was requested but ECHILD was received by waitpid(). See the documentation of g_child_watch_source_new() for possible causes.

The warning does not present if you build with GLib 2.74.0 however.

[bobby285271]

Okay, sounds like waitpid is the correct way, let's just do this conditionally: cockpit-project/cockpit#17564 Ah no, see the PR below, which uses pidfd

[T-O-R-U-S]

I'm also experiencing this freeze when trying to close the terminal -- though I'm not running the official distro of Elementary, I'm running Pantheon on my Arch install.