Closing a user session does not stop all services running for that user

[tmarplatt]

 * Cinnamon version 5.0.7
   - Not using the daily builds PPA
 * Mint 20.2
 * Geforce discrete graphics with nvidia drivers
 * 64 bit

Issue
Hello! I'm running Mint 20.2 Cinnamon on a laptop that I share with the family. It's configured to automatically load one user account after boot. After closing said user session and logging in with a different user account, I realized by running htop that several services remain running for that user.

This is a problem for example with services like blueberry-obex-agent, where it breaks file receiving over Bluetooth: there are two bt-obex daemons running at the same time, and attempting to receive a file over Bluetooth produces an error regarding file permissions (0x43 Forbidden). I am currently working around this issue by disabling automatic user session login (although it persists when closing and logging in with another user).

I have not tested other duplicated daemons but this case is enough on its own.

Steps to reproduce
In a computer configured with at least two user accounts:

1. Log in as one user.
2. Log out
3. Log in as the other user
4. Examine running processes, observe several services remain running owned by the first user.

Expected behaviour
User services should stop running on closing a Cinnamon user session.

Other information
I love Cinnamon regardless, great work devs! 🤩

[leigh123linux]

It isn't cinnamons job to clean up, logind should do it.

Try editing /etc/systemd/logind.conf and change

#KillUserProcesses=no

to

KillUserProcesses=yes

[tmarplatt]

I see, thank you.

And I can imagine how defaulting KillUserProcesses=yes might not be a safe choice, but then what's the solution to having several users needing to use the same daemon (of which two or more instances enter conflict) after switching sessions? Like in the case of blueberry and Bluetooth.