bug#28630: 27.0.50; C-g while a non-main thread is sitting crashes Emacs

[YAMAMOTO Mitsuharu]

>>>>> On Mon, 02 Oct 2017 13:30:44 +0900, YAMAMOTO Mitsuharu 
>>>>> <mituharu@math.s.chiba-u.ac.jp> said:

> The secondary thread seems to be still blocking in a pselect call
> when crash occurs.  Maybe SIGIO (and SIGALRM) should be unmasked in
> the secondary thread that calls pselect for keyboard input, and the
> main thread should forward the delivery of these signals to the
> secondary (or mask them) so that the pselect call in the secondary
> thread can be interrupted.

Sorry.  The stacks seem to be already clobbered by (bad) longjmp.  So
the above analysis would be bogus.

                                     YAMAMOTO Mitsuharu
                                mituharu@math.s.chiba-u.ac.jp