bug#16387: 24.3.50; unquittable infloop

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 07 Jan 2014 11:53:23 -0500
> From: Richard Stallman <rms@gnu.org>
> 
> 
> M-x grep put me in a loop I could not quit out of.
> Here's the backtrace after C-g C-g put me into GDB.
> Grep had already terminated, but Emacs had not exited the loop
> even a minute later.
> 
> It happened twice today.  One time, the current buffer was in Mail mode,
> and maybe that was true both times.
> 
> 
> #0  0x76a4d3c4 in kill () from /lib/libc.so.6
> #1  0x00657004 in sys_suspend () at sysdep.c:450
> #2  0x0063fcf8 in handle_interrupt (in_signal_handler=true) at keyboard.c:10318
> #3  0x0063fb18 in handle_interrupt_signal (sig=2) at keyboard.c:10259
> #4  0x006599b0 in deliver_process_signal (sig=2, 
>     handler=0x63fa78 <handle_interrupt_signal>) at sysdep.c:1568
> #5  0x0063fb74 in deliver_interrupt_signal (sig=2) at keyboard.c:10266
> #6  <signal handler called>

Any idea why sys_suspend is on the call stack?  Did you really type
C-z?