bug#34059: 27.0.50; Emacs hangs on typing quit (MS-Windows)

[Eli Zaretskii <eliz@gnu.org>]

> From: Richard Copley <rcopley@gmail.com>
> Date: Sun, 13 Jan 2019 16:00:23 +0000
> Cc: 34059@debbugs.gnu.org
> 
> On Sun, 13 Jan 2019 at 15:17, Eli Zaretskii <eliz@gnu.org> wrote:
> >
> > > From: Richard Copley <rcopley@gmail.com>
> > > Date: Sun, 13 Jan 2019 13:04:05 +0000
> > >
> > > Emacs sometimes hangs on typing quit, on MS-Windows.
> >
> > Thanks, but if you can, please provide more details about what was
> > Emacs doing when this happens.
> 
> I'm not sure exactly, sorry. I would have been reading console output
> from a process in a compilation-mode buffer, and using git via magit,
> around the time.

Any chance you could recollect why did you type C-g while at that?

> > > (See also <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=25279#69>.)
> >
> > That one was fixed, AFAIU.
> 
> The message says "I'll send another report if and when I catch another hang".

I've found one, possibly two more places where we could QUIT while
holding a critical section.  I cannot know if they were part of your
hang, but I went ahead and fixed them on the emacs-26 branch.  Let's
see if they stop these hangs from happening.

Thanks.