Re: PATCH: 3.1.6-dev-17 (Was: BUG: backgrounding zsh does bad tty stuff)

["Bart Schaefer" <schaefer@candle.brasslantern.com>]

On Feb 12, 11:17pm, Geoff Wing wrote:
} Subject: PATCH: 3.1.6-dev-17 (Was: BUG: backgrounding zsh does bad tty stu
}
} :There's even a loop in init.c:init_io() where zsh repeatedly attempts to
} :force itself to be the tty foreground process
} 
} My problem is that zsh gets past that loop when it should be stuck there.
} This seems to fix it for me:  we shouldn't be making ourself the process
} group leader for the terminal until our parent has told has we're really
} the process group leader.

If the parent has made zsh the tty group leader -- note we're testing
ttpgrp == mypgrp -- then why would zsh need to make itself the tty group
leader?  It doesn't make sense to me to call attachtty() *after* we've
already verified that zsh is the tty group leader.

Perhaps what you mean is that we should wait for our parent to put us in
our own process group before attempting to make that group the tty group?

That isn't what your patch accomplishes, though.

} Also, I don't know why the sleep(1) is in there.

Note that we call GETPGRP() both before and after the sleep(1).  The
sleep is there to give the parent a chance to assign zsh to its own
group, i.e., have the OS context-switch to the parent and back before
we attempt GETPGRP() the second time.

Try this patch instead of 9692.  The difference that I see with the
patch below is that instead of

[1]  + suspended (tty output)  Src/zsh -f

with zsh stopped in ioctl() (according to gdb), I instead get

[1]  + suspended (tty input)  Src/zsh -f

with zsh stopped in its own call to killpg() -- which I think is the
desired behavior.

Index: Src/init.c
===================================================================
@@ -399,11 +399,12 @@
 #ifdef JOB_CONTROL
     /* If interactive, make the shell the foreground process */
     if (opts[MONITOR] && interact && (SHTTY != -1)) {
-	attachtty(GETPGRP());
 	if ((mypgrp = GETPGRP()) > 0) {
 	    while ((ttpgrp = gettygrp()) != -1 && ttpgrp != mypgrp) {
-		sleep(1);
+		sleep(1);	/* give parent time to change pgrp */
 		mypgrp = GETPGRP();
+		if (mypgrp == mypid)
+		    attachtty(mypgrp);
 		if (mypgrp == gettygrp())
 		    break;
 		killpg(mypgrp, SIGTTIN);

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com