[Bug 1584393] Re: systemctl restart networking hangs reloading ssh.service

[Martin Pitt]

This indeed looks like a deadlock. It could  be broken by openssh's if-
up.d script if it reloads ssh asynchronously instead of blocking on it.
It would be even better to finally get rid of this silly hack and make
openssh use IP_FREEBIND properly :-)

I'm very reluctant to make invoke-rc.d reload itself async. This is too
regression prone, as a scripts might depend on the reload actually being
done after the call.

Also, low priority. Restarting "networking" has never worked under
upstart at all, and it mostly works now (can't reproduce this on several
machines). So this is mostly a case of "don't do that then"..

** Package changed: ifupdown (Ubuntu) => openssh (Ubuntu)

** Changed in: openssh (Ubuntu)
   Importance: Undecided => Low

** Changed in: openssh (Ubuntu)
       Status: Confirmed => Triaged

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https://bugs.launchpad.net/bugs/1584393

Title:
  systemctl restart networking hangs reloading ssh.service

Status in openssh package in Ubuntu:
  Triaged

Bug description:
  Issues "systemctl restart networking" never exits. It hangs during a
  call to "systemctl reload ssh.service":

  ● networking.service - Raise network interfaces
     Loaded: loaded (/lib/systemd/system/networking.service; enabled; vendor preset: enabled)
    Drop-In: /run/systemd/generator/networking.service.d
             └─50-insserv.conf-$network.conf
     Active: activating (start) since Sat 2016-05-21 21:41:58 UTC; 18s ago
       Docs: man:interfaces(5)
    Process: 1288 ExecStop=/sbin/ifdown -a --read-environment (code=exited, status=0/SUCCESS)
    Process: 1376 ExecStartPre=/bin/sh -c [ "$CONFIGURE_INTERFACES" != "no" ] && [ -n "$(ifquery --read-environment --list --exclude=lo)" ] &
   Main PID: 1383 (ifup)
      Tasks: 7 (limit: 512)
     Memory: 1.8M
        CPU: 111ms
     CGroup: /system.slice/networking.service
             ├─1383 /sbin/ifup -a --read-environment
             ├─1479 /sbin/dhclient -1 -v -pf /run/dhclient.enp0s3.pid -lf /var/lib/dhcp/dhclient.enp0s3.leases -I -df /var/lib/dhcp/dhclient6
             ├─1480 /bin/sh -c /bin/run-parts --exit-on-error /etc/network/if-up.d
             ├─1481 /bin/run-parts --exit-on-error /etc/network/if-up.d
             ├─1504 /bin/sh /etc/network/if-up.d/openssh-server
             ├─1507 /bin/sh /usr/sbin/invoke-rc.d ssh reload
             └─1527 systemctl reload ssh.service

  Then issuing the same command from another terminal causes the first
  to exit successfully (the second also exists successfully).

  On the official vagrant image, I get this problem independently of
  whether the command is issued through and ssh session. I've gotten the
  same behavior on the official xenial AMIs.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: ifupdown 0.8.10ubuntu1
  ProcVersionSignature: Ubuntu 4.4.0-22.40-generic 4.4.8
  Uname: Linux 4.4.0-22-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2
  Architecture: amd64
  Date: Sat May 21 21:35:08 2016
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: ifupdown
  UpgradeStatus: No upgrade log present (probably fresh install)

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