bug#63865: 29.0.90; call-process while owning the X selection hangs other processes

[Po Lu]

Spencer Baugh <sbaugh@janestreet.com> writes:

> Other things which make Emacs busy still let Emacs respond to X
> selection requests.

Only if Emacs is still reading keyboard input.  Responding to selection
requests is only possible when it is safe to run Lisp.  A cursory
examination of xselect.el will show why.