Bug#737825: another hang of systemd-tty-ask-password-agent

[Ralf Schlatterbeck]

I've recently tried to upgrade a running debian testing system.
It hung on upgrade of network-manager.
Now if I manually start
dpkg --pending --configure
network manager fails to start and the process hanges.

To confirm it is waiting on systemd-tty-ask-password-agent see the
following output of ps auxwww --forest on the machine, note that
another process is also hanging waiting for 
/bin/systemd-tty-ask-password-agent


USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
...
root      4597  0.0  0.1  25824  5292 tty1     S    17:53   0:01  \_ -bash
root      9657  0.0  0.1  24124  7436 tty1     T    18:50   0:00      \_ dpkg --pending --configure
root      9658  0.0  0.0   4328   756 tty1     T    18:50   0:00      |   \_ /bin/sh /var/lib/dpkg/info/network-manager.postinst configure 
root      9661  0.0  0.0   4328  1456 tty1     T    18:50   0:00      |       \_ /bin/sh /usr/sbin/invoke-rc.d dbus force-reload
root      9692  0.0  0.0  24904  2640 tty1     T    18:50   0:00      |           \_ systemctl reload dbus.service
root      9693  0.0  0.0  13168  1532 tty1     T    18:50   0:00      |               \_ /bin/systemd-tty-ask-password-agent --watch
root      9703  0.0  0.0  21680  2524 tty1     R+   18:58   0:00      \_ ps auxwww --forest
root      9191  0.0  0.0   4328  1332 ?        S    18:34   0:00 /bin/sh /usr/sbin/invoke-rc.d dbus force-reload
root      9222  0.0  0.0  24904  2656 ?        S    18:34   0:00  \_ systemctl reload dbus.service
root      9223  0.0  0.0  13168  1684 ?        S    18:34   0:00      \_ /bin/systemd-tty-ask-password-agent --watch

Note that I'm logged in as root on the first tty. No need to 
ask me for a password here.

Then I tried to replace /bin/systemd-tty-ask-password-agent
with a link to /bin/true. But it's still hanging. Note that
I killed all hanging processes before trying this. Now I get:


USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
...
root      4597  0.0  0.1  25824  5292 tty1     S    17:53   0:02  \_ -bash
root      9841  0.2  0.1  24124  7392 tty1     S    19:05   0:00      \_ dpkg --pending --configure
root      9842  0.0  0.0   4328   792 tty1     S    19:05   0:00      |   \_ /bin/sh /var/lib/dpkg/info/network-manager.postinst configure 
root      9845  0.0  0.0   4328  1436 tty1     S    19:05   0:00      |       \_ /bin/sh /usr/sbin/invoke-rc.d dbus force-reload
root      9876  0.0  0.0  24904  2592 tty1     S    19:05   0:00      |           \_ systemctl reload dbus.service
root      9877  0.0  0.0      0     0 tty1     Z    19:05   0:00      |               \_ [systemd-tty-ask] <defunct>
root      9884  0.0  0.0  21680  2472 tty1     R+   19:06   0:00      \_ ps auxwww --forest
...

So it looks like reloading dbus doesn't work.
Note that dbus *is* running:

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
...
message+   493  0.0  0.0  42352  3624 ?        Ss   09:51   0:10 /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation
...

If you suggest any further tries / experiments, this
machine isn't production so I can try all sort of stuff.

Ralf
-- 
Ralf Schlatterbeck             email: ralf at zoo.priv.at