Hercules lack of Linux "suspend/resume" support (i.e. Ctrl+z, `fg`, etc) causes problems with e.g. tmux

[wyan]

On Linux, running Hercules under tmux, accessed remotely via ssh.

If I accidentally press Ctrl-Z and the job gets suspended, when I bring it back to the foreground with fg the console stops working properly, ignoring some keypresses (especially PgUp/PgDown, arrows, etc). If I press Esc to go to the Hercules front panel in this state, the console scrambles even more, not displaying the full front panel, and becoming incapable of processing the Esc key (thus completely disabling the console at all).

The only solution I've found to this is to kill Hercules (since it can't be quit anymore from this state), which doesn't allow for the guest OS to be shut down properly.

[ivan-w]

I am going to go out on a limb and saying that the effects of CTRL-Z (or rather receiving the SIGSTP signal) will probably trigger events in the shell that invoked the Hercules command, which may lead to the topmost shell in the process group to issue a certain number of adjustments to the controlling terminal in order to make it usable. Returning the original process to the foreground (usually fg - which sends the SIGCONT signal) may not reset everything to its original state.

This is more probably an issue with the shell being used on your POSIX like system in itself rather than with Hercules. I am not certain that trapping SIGSTP is the proper way to do it. Other fullscreen applications (think vi/vim/etc..) seem to be able to handle it, so I need to check that out.

I would not consider this a high priority issue (simple workaround answer would be: don't press CTL-Z!) - although it might be an issue if you are trying to send CTRL-Z to the integrated console. One possible option as an actual workaround is to re-assign the stty 'susp' to something else than CTRL-Z before invoking Hercules and then reset it back afterwards.

--Ivan

[ivan-w]

Update... I haven't tried this yet, but did anyone try to send CTRL-Z to the integrated console using CTRL-V+CTRL-Z? (I'll try it soon)...

[Fish-Git]

What's the word in this issue? Is it a bug in Hercules or not? Based on what Ivan has said, it sounds like it's something outside of Hercules's control, and therefore not a bug in Hercules. Being unfamiliar with Linux however, I cannot be sure. Should we close this issue as "Unknown"? Or keep it open? (and if so, should we label it as "Bug"?)

Thanks.

[marXtevens]

What OS is running in Hercules?
Do you have a [tn|pw|x]3270 session open to that OS?

[marXtevens]

In the mean time, please try the following.

1. Hercules is running
2. Press Ctrl-Z
3. Enter fg & press Enter
4. Press the ESC key to verify you have Hercules attention. It displays something, even though garbled.
5. Press Ctrl-D
6. Execute the command that you used to start Hercules.
7. You might be back where you have the console available again.

I tried this several times and it seemed to work each time, giving me access to the OS (VM/370 CE) which was running in Hercules.

I Hope This Helps.

[wyan]

@marXtevens I don't get your solution... Ctrl-D kills Hercules, which is what I want to avoid in the first place.

[marXtevens]

Entering Ctrl-Z cripples Hercules. Yes, Ctrl-D does kill it ... BUT ... restarting Hercules using the exact command you used the first time, starts Hercules, and it picks up where it left off when you press Ctrl-Z. I tried this four-five times, and it reattached to my VM/370 CE system every time, and I could continue working, without shutting down, or having to re-IPL the system Hercules was supporting. Try it. I think you'll like it.

[wyan]

Just did. It just re-IPLs the system...

[marXtevens]

What OS is running in Hercules?
Do you have a [tn|pw|x]3270 session open to that OS?

[marXtevens]

wyan,

I guess I misunderstood what you said originally. Sorry for that. So no Ctrl-D.

If you resize your terminal, 80x24 to 43x80, or similar, does Hercules redraw correctly?

If you press Escape after it redraws, do you go back to the console?

[marXtevens]

Fish,

Does Hercules expect an xterm/VT-100 compatible terminal to display its information in?