bug#51229: 28.0.50; [PATCH] Mitigate Blandyism on thread signals

[Eli Zaretskii]

> Date: Fri, 15 Oct 2021 22:11:32 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 51229@debbugs.gnu.org
> 
> > diff --git a/src/thread.c b/src/thread.c
> > index 714b1cd903..d7dce6cc8e 100644
> > --- a/src/thread.c
> > +++ b/src/thread.c
> > @@ -122,6 +122,7 @@ post_acquire_global_lock (struct thread_state *self)
> >  
> >        current_thread->error_symbol = Qnil;
> >        current_thread->error_data = Qnil;
> > +      clear_waiting_for_input();
> >        Fsignal (sym, data);
> >      }
> 
> That's a non-starter, not unless you explain why this is not needed
> for threads, because it attempts to artificially remove a restriction
> without any analysis or rationale.  Why is a non-main thread waiting
> for input different from the main thread waiting for input?

I've installed a fix on the emacs-28 branch, please test.