I can confirm this behaviour on my system exactly as described. Besides the message
swapoff: /dev/sdxx: swapoff failed: Cannot allocate memory there are also these lines: dev-sdxx.swap swap process exited, code=exited status=255 Unit dev-sdxx.swap entered failed state. I also have set overcommit_memory=2 and in my case Commited_AS is above MemTotal when the system is running. But when the system got stuck during shutdown, I can see that this is not true anymore, i. e. the processes which commited memory were stopped and Committed_AS is well beyond MemTotal. Manually doing a 'swapoff -a' on the debug shell allows the system to continue with a proper shutdown or reboot. I "fixed" it somehow by removing the swap partition from /etc/fstab, creating an own systemd service for handling swap and adding a dependency for the process which needs to commit some memory: [Unit] Description=swap on /dev/sdxx Before=some.service [Service] User=root Group=root Type=oneshot RemainAfterExit=yes ExecStart=/sbin/swapon /dev/sdxx ExecStop=/sbin/swapoff /dev/sdxx [Install] WantedBy=multi-user.target I know that this is not a good solution, but it seems to work at least for my configuration.
