On Tue, 24 Apr 2012, Denys Vlasenko wrote:
On Tue, Apr 24, 2012 at 1:18 PM, Tomasz Czapiewski <[email protected]> wrote:On Tue, 24 Apr 2012, Denys Vlasenko wrote:On Tue, Apr 24, 2012 at 11:27 AM, Tomasz Czapiewski <[email protected]> wrote:dmesg: Mon Apr 23 23:16:57 2012: process '/sbin/getty -L ttyS0 115200 vt102' (pid 909) exited. Scheduling for restart. I'm also getting "getty: setsid: Operation not permitted" when trying to run above command from shell.It means that setsid fails. We used to just assume it always succeeds. Which was wrong. For one, successful setsid drops ctty, but failing one does not. setsid fails if getty is started in a way so that it is a process leader, but not a session leader. For one, this is what happens when you run a single command (not a pipe) from interactive shell: it is made a process leader by the shell. That's why getty from interactive shell doesn't work (and probably is not expected to). How do you start your getty? From init? Which init - busybox's?Yes, it's started from init, which is a symlink to the same busybox binary. /etc/inittab: ::sysinit:/etc/init.d/rcS ttyS0::respawn:/sbin/getty -L ttyS0 115200 vt102 ::ctrlaltdel:/sbin/reboot null::shutdown:/bin/umount -a -r (changing order of ttyS0 and 115200 arguments doesn't seem to make any difference)This is strange. bbox init always puts its children in their own sessions (meaning it makes them session leaders). See run() function in init.c: it does setsid() in the child, immediately after [v]fork.
My BusyBox build contains just minor change (diff in attachment), which TV vendor has made on BusyBox 1.2.1 and I keep it on BB upgrades.
But I don't think it should be related.
Let's verify that.
Can you add a debugging printout in getty_main() here?
/* Create new session and pgrp, lose controlling tty */
bb_error_msg("pid:%d", getpid());
bb_error_msg("sid:%d", getsid(0));
pid = setsid(); /* this also gives us our pid :) */
if (pid < 0) {
...
run it and tell me what do you observe?
--
vda
Would you change the code above to log via kmsg so I could read them via dmesg? It's currently quite problematic for me to estabilish serial connection (lack of hardware at the moment).
Tom
busybox-1.20.0.diff.gz
Description: Binary data
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