Bug#314727: [Pkg-shadow-devel] Bug#314727: login: suspend command from su shell fails to return to parent shell

[Alexander Gattin]

Hi!

On Sun, Jun 19, 2005 at 12:52:12AM +0200, Nicolas François wrote:
> I can also reproduce it.

Me too, except for "no characters echoed" symptom.

> It is caused by the new setting of CLOSE_SESSIONS
> to yes in /etc/login.defs.

Excellent analysis.
I came to conclusion that suspend returns control to
its parent process, which is "su" in the below
examples:

 4957 ?        S      0:00              \_ xterm
 4958 pts/2    Ss     0:00                  \_ bash
 4961 pts/2    S      0:00                      \_ su -
 4963 pts/2    S      0:00                          \_ -su
 4969 pts/2    R+     0:00                              \_ ps -A f

In the above example `su -` was used, and therefore
child bash is called "-su" because it's treated like
login shell by "dashed su".

 4941 ?        S      0:00              \_ xterm
 4942 pts/1    Ss     0:00              |   \_ bash
 5042 pts/1    S      0:00              |       \_ su
 5044 pts/1    S      0:00              |           \_ bash
 5047 pts/1    R+     0:00              |               \_ ps -A f

This is for `su` without dash -- here you clearly see
where is child bash located WRT parent _shell_.

So, immediate parent of bash would be su and not
parent bash.

> To perform CLOSE_SESSIONS, a fork is needed, and when the shell is
> suspended, the whole process is not completely suspended and thus the
> previous shell (used to su) do not get the focus.

About fork you are right, but for the other I seem
to not understand your point.

> So, setting CLOSE_SESSIONS to no will solve this issue (but won't close
> this bug).

Yes, here we have:

 4941 ?        S      0:01              \_ xterm
 4942 pts/1    Ss     0:00              |   \_ bash
 5063 pts/1    S      0:00              |       \_ bash
 5067 pts/1    R+     0:00              |           \_ ps -A f

Here you can see that parent and child shells don't
have intermediate "su" process between them.

> I still don't know how to fix this issue with CLOSE_SESSIONS set to yes.

Wontfix?

> I noted that if "su -" is used, then bash reports:
> suspend: cannot suspend a login shell
> That may be an hint.

IMHO, this is just a warning that user will be simply
locked on that particular terminal, because login shell
usually is SHLVL==1, i.e. don't have a parent shell.

-- 
WBR,
xrgtn