Bug#791412: systemd invoking a service on its own

[Ritesh Raj Sarraf]

Responding back in rich text, so that the code formatting doesn't annoy
the reader.


On Monday 06 July 2015 01:28 PM, Michael Biebl wrote:
> > Something like that is going in the right direction. > You are
backgrounding the subshell here, so there might still be issue > that
the lmt-udev script is killed before you can call systemctl. > So I
suspect there is still a race condition. I guess you could test > that
by simply adding a sleep 10 before systemctl --non-block. > > I would
suggest moving the systemctl code outside of the backgrounded >
subshell, i.e. the ( ) ... code block > > See [1] as an example. >


Thank you. That was a very helpful example.

So now I have:

        rrs at learner:~$ cat /lib/udev/lmt-udev
        #!/bin/sh -e


        # /usr is not guaranteed to be mounted when udev starts
        non_systemd_way() {
                if [ -e /lib/udev/hotplug.functions ]; then
                        . /lib/udev/hotplug.functions
                        wait_for_file /usr/sbin/laptop_mode
                        exec /usr/sbin/laptop_mode "$@"
                else
                        file=$1
                        timeout=$2
                        [ "$timeout" ] || timeout=120

                        count=$timeout
                        while [ $count != 0 ]; do
                                [ -e "/usr/sbin/laptop_mode" ] && exec
        /usr/sbin/laptop_mode "$@" && return 0
                                sleep 1
                                count=$(($count - 1))
                        done

                        mesg "$file did not appear before the timeout!"
                        exit 1
                fi
        }



        # Under systemd, we don't do synchronous operations, so we can
        run in the foreground;
        # And we need also need to run in foreground, because forked
        children get kill immediately
        # under systemd/udev

        if [ -d /run/systemd/system ]; then
                exec systemctl --no-block reload
        laptop-mode                                          
        else                                                                                          

                # Under sysvinit/upstart, we need to fork as we start
        the long-running                
                # /usr/sbin/laptop_mode
        process.                                                      
               
        #                                                                                     

                # Also, if this happens during boot, we may want to wait
        until /usr is available      
                # This else stanza is going to be used rarely, because
        going forward we are           
                # going to use
        systemd.                                                               

                # But for compatibility reasons, we'll carry
        this                                     
               
        #                                                                                     

                # That said, we background the execution here, becauser,
        otherwise udevd will wait    
                # for this process which will block

                exec > /dev/null 2>dev/null
                non_systemd_way "$@" &
        fi

        exit 0
        16:42 ♒♒♒  ☺   



And the best part is, now, when my users will ask systemctl for a status
on laptop-mode.service, they'll get all invocations accounted.

        rrs at learner:~$ sudo systemctl status laptop-mode.service
        ● laptop-mode.service - Laptop Mode Tools
           Loaded: loaded (/lib/systemd/system/laptop-mode.service;
        enabled; vendor preset: enabled)
           Active: active (exited) since Mon 2015-07-06 16:29:16 IST;
        19min ago
          Process: 5579 ExecReload=auto (code=exited, status=0/SUCCESS)
          Process: 1124 ExecStart=init auto (code=exited, status=0/SUCCESS)
         Main PID: 1124 (code=exited, status=0/SUCCESS)
           CGroup: /system.slice/laptop-mode.service

        Jul 06 16:29:16 learner laptop-mode[1237]: enabled, not active
        Jul 06 16:29:16 learner systemd[1]: Started Laptop Mode Tools.
        Jul 06 16:39:08 learner laptop-mode[4322]: Laptop mode
        Jul 06 16:39:08 learner laptop-mode[4323]: enabled, not active
        [unchanged]
        Jul 06 16:39:08 learner systemd[1]: Reloaded Laptop Mode Tools.
        Jul 06 16:39:22 learner laptop-mode[4385]: enabled, active
        Jul 06 16:39:23 learner systemd[1]: Reloaded Laptop Mode Tools.
        Jul 06 16:41:07 learner laptop-mode[4921]: enabled, not active
        Jul 06 16:41:07 learner systemd[1]: Reloaded Laptop Mode Tools.
        Jul 06 16:44:41 learner systemd[1]: Reloaded Laptop Mode Tools.
        16:48 ♒♒♒  ☺   



So now, I'm going to add similar check conditions for the pm-utils hook
and the acpid hook.

-- 
Ritesh Raj Sarraf | http://people.debian.org/~rrs
Debian - The Universal Operating System


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