Re: Emacs 22.0.50 and suspending while logged into another system

[Quanah Gibson-Mount]

--On Sunday, October 15, 2006 12:20 AM -0400 Richard Stallman <rms@gnu.org> 
wrote:

>     In any case, you now have the information on what "tty" contained
> after it      exited from EMACS_SET_TTY, and I'll leave it up to you and
> the other      developers to decide whether or not that data was 'bad' or
> not.
>
> Did you examine that value just before the failure?
> That is, did it fail just after this call to init_sys_modes?
> init_sys_modes will be called each time you resume Emacs after
> suspending; the time that we need to see the value
> is the time that it fails.
>
> It would be good to see the value of tty after EMACS_SET_TTY,
> and the value of old_tty too.

Hi Richard,


I set up the following in gdb:

l sysdep.c:1637
break 1637

(this is the line after EMACS_SET_TTY is called in the source I have).

Then, I

run -nw

Then use control-Z to suspend.

This *usually* then breaks at line 1637.  If this is where the break 
occurs, everything continues to work as desired.

However, sometimes it breaks in _libc_kill instead, completely bypassing 
EMACS_SET_TTY.
After this, things don't work correctly.  So it appears that the same logic 
is not always being followed when a SIGTSTP is caught.


The usual path I get is:

(control-Z):
Breakpoint 1, init_sys_modes () at sysdep.c:1642
1642          if (!flow_control) ioctl (input_fd, TCXONC, 1);
(gdb) cont
Program received signal SIGTSTP, Stopped (user).
0xfe6990cc in _poll () from /usr/lib/libc.so.1
(gdb)


Then I issue "signal SIGCONT" to resume.

On the other path:

(control-Z):
Program received signal SIGTSTP, Stopped (user).
0xfe69b638 in _libc_kill () from /usr/lib/libc.so.1

I tried "step"ing from here, but it just hangs forever, without entering 
init_sys_modes.

I can reproduce this very easily.  If I give a "signal SIGCONT" here, then 
it'll let me back into emacs.

--Quanah

--
Quanah Gibson-Mount
Principal Software Developer
ITS/Shared Application Services
Stanford University
GnuPG Public Key: http://www.stanford.edu/~quanah/pgp.html