bug#34535: 27.0.50; emacs -nw: while-no-input + sit-for + <KEY> => Quit

[Eli Zaretskii]

> From: Michael Heerdegen <michael_heerdegen@web.de>
> Cc: monnier@iro.umontreal.ca,  34535@debbugs.gnu.org
> Date: Mon, 25 Feb 2019 08:09:27 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Thanks for testing.  I'll push the change in a few days, if nothing
> > pops up to the contrary.
> 
> Dunno if this is related, but I think it started happening at the time I
> installed your patch: When I wake up my Laptop from suspend-to-ram,
> Emacs uses 100% CPU and it's hard to interrupt it (C-g doesn't
> help).

The only way to be sure is to back out the patch and see if these
problems go away.

> I sent a SIGUSR2 and got this backtrace:
> 
> Debugger entered--entering a function:
> * command-error-default-function((quit) "" nil)

This isn't informative enough, I need a C-level backtrace plus a full
Lisp backtrace.  Please next time attach a debugger when this happens,
source Emacs's src/.gdbinit, and type "thread apply all bt" at GDB
prompt.

Also, I don't think I understand how you got the above Lisp backtrace:
by default SIGUSR2 does nothing.  Do you have some handler for it? if
so, what does it do?

Thanks.