Bug#819239: FUSE + linger = stuck shutdown at unmount

[Yuri D'Elia]

Package: systemd
Version: 229-3
Severity: normal

I've been having problems at shutdown since I've switched to systemd, but due
to the inability of debugging systemd during shutdown it's a bit tricky to know
exactly what's going on. I apologize in advance for not having fully debugged
this, but I need some assistance.

I'm using sshfs in combination with user lingering. When I initiate a shutdown,
it generally gets stuck while unmounting /home because it's busy.

I realized this only happens when I had an active sshfs mount. Since I have
user lingering enabled, I assume sshfs itself is not killed when the session is
closed.

I have a couple of questions:

- Does systemd try to unmount FUSE filesystems at shutdown? (Should it try at all?)

  Please note that in this case, sshfs requires the network to shutdown
  correctly, so it might be that it's being unmounted after the network is not
  available anymore, causing unmount to get stuck anyway.

- Does systemd still try to kill all remaining user processes before unmounting?

  This used to be a step in sysv-init in order to release all filesystems
  before unmounting. In theory, user processes are released when stopping the
  user session, but this is not true when user lingering is enabled. You might
  still need to kill pending user processes before unmounting.

Thanks.

-- Package-specific info:

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (900, 'unstable'), (800, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 4.5.0-trunk-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages systemd depends on:
ii  adduser         3.114
ii  libacl1         2.2.52-3
ii  libapparmor1    2.10-3+b1
ii  libaudit1       1:2.4.5-1+b1
ii  libblkid1       2.27.1-6
ii  libc6           2.22-4
ii  libcap2         1:2.24-12
ii  libcap2-bin     1:2.24-12
ii  libcryptsetup4  2:1.7.0-2
ii  libgcrypt20     1.6.5-2
ii  libgpg-error0   1.21-2
ii  libkmod2        22-1
ii  liblzma5        5.1.1alpha+20120614-2.1
ii  libmount1       2.27.1-6
ii  libpam0g        1.1.8-3.2
ii  libseccomp2     2.2.3-3
ii  libselinux1     2.4-3+b1
ii  libsystemd0     229-3
ii  mount           2.27.1-6
ii  util-linux      2.27.1-6

Versions of packages systemd recommends:
ii  dbus            1.10.8-1
ii  libpam-systemd  229-3

Versions of packages systemd suggests:
ii  systemd-container  229-3
ii  systemd-ui         3-4

Versions of packages systemd is related to:
ii  udev  229-3

-- Configuration Files:
/etc/systemd/journald.conf changed [not included]
/etc/systemd/resolved.conf changed [not included]
/etc/systemd/timesyncd.conf changed [not included]