Re: connecting to a lost server process

[Eli Zaretskii <eliz@gnu.org>]

> Date: 12 Jul 2019 06:20:57 -0000
> From: Madhu <enometh@meer.net>
> 
> The socket is still open as can be seen in /proc/<emacspid>/fd/ - is
> there some linux arcana that can be exploited to connect to it?
> 
> Earlier it used to be possible to gdb attach to the emacs process and
> to restart the server. Something like
> Feval(Fcar(Fread_from_string(build_string("(server-start)"),Qnil,Qnil)),Qnil)
> But for some time now that route hits a
> terminate_due_to_signal. (Apparently make-network-process tries to
> signal an error which calls emacs_abort which ends the show)

Please report a bug with the details of that crash, it may or may not
be a bug.

> [Unfortunately recently the robustness of the server mechanism has gone
> down - (especially since elogind).  Typically I set
> XDG_RUNTIME_DIR=/dev/shm/<username> in my environment and start a
> server which i expect to survive restarts in dbus, elogind etc.  That
> seems no longer possible even when using a --without-x emacs.]

Did you try to bind a function to sigusr1 or sigusr2 event, and have
that function restore the server file?