bug#36609: 27.0.50; Possible race-condition in threading implementation

[Eli Zaretskii]

> Date: Fri, 12 Jul 2019 21:27:40 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 36609@debbugs.gnu.org, politza@hochschule-trier.de
> 
> Sorry, I don't want to call unwind-protect there.  Call me paranoid,
> if you want.

Maybe I should explain the rationale behind that paranoia.  The main
reason is that you are proposing to do that inside code that can
switch threads.  Switching threads means switching to another stack
and also to another set of handlers.  So using the unwind-protect
machinery in this situation is IMO asking for trouble.

And then there's the TTY frame case, where C-g triggers SIGINT, and we
actually longjmp from wherever we were...