init problems (feature or bug?)

[Luciano Miguel Ferreira Rocha]

On Mon, Jan 08, 2007 at 02:13:51PM +0100, Dirk Clemens wrote:
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> I have found an init problem:
> 
> - --------------- Example 1 ---------------
> 
> 
> - --- file /etc/inittab ---
> ::shutdown:/etc/halt
> - --- end --
> 
> - --- file /etc/halt ---
> kill -TERM -1
> sleep 5
> kill -KILL -1
> sleep 5
> umount -a
> - --- end --
> 
> After the first kill, /etc/halt will also be terminated.
> The second kill will never be executed.
> 

Is that kill a shell internal command or an external command? If the
later, then it is expected for it to signal all processes except itself
(on Linux) and init.

> 
> - --------------- Example 2 ---------------
> 
> - --- file /etc/inittab ---
> ::shutdown:/etc/halt1
> ::shutdown:/etc/halt2
> - --- end --
> 
> - --- file /etc/halt1 ---
> kill -TERM -1
> sleep 5
> kill -KILL -1
> sleep 5
> - --- end --
> 
> - --- file /etc/halt2 ---
> sleep 20
> do_something
> - --- end --
> 
> After the first kill /etc/halt2 is started and both
> /etc/halt1 and /etc/halt2 runs at same time.
> 
> 
> - -----------------
> 
> The reason is: init creates a sub process (#A) and that
> sub process create a new sub process (#B) which will execute
> the code or script. And #A is not roust against signals.

#A can *never* be robust against -KILL.

> So if the script in #B uses 'kill -TERM -1', #A will be
> killed and init thinks, that the job has finished
> 
> In example 1 init thinks that shutdown is done
> and kills itself all other processes.
> 
> In example 2 init thinks that halt1 is done and
> starts halt2, so that both runs together.
> 
> I have the same effects when using bash internal kill
> or busybox kill.

I have no problems with something like this:
killall5 -15
sleep 1
killall5 -9

And the killall5 (I use bash) is:
#!/bin/sh

sig="${1:--15}"
pids=(/proc/[0-9]*)
for pe in ${pids[*]}; do
        # disappeared
        [ -d $pe ] || continue
        # kernel thread
        [ -f $pe/exe ] || continue
        # p = pid
        p="${pe##*/}"
        # init
        [ "$p" -eq "1" ] && continue
        # parent
        [ "$p" -eq "$PPID" ] && continue
        # self
        [ "$p" -eq "$$" ] && continue
        kill $sig $p
done

-- 
lfr
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