"TASK MANAGER" process is taking over a single-user mode database. What is it?

This is a duplicate of the question I asked on stackoverflow, but I was advised, that someone here could have a better idea what is happening.

I have a sporadic problem, when upgrading SQL Server in a single-user mode, using .NET SqlConnection, some other application somehow logs into the database, while the SQL code is being executed, and kicks my process out. SqlConnection is not closed or disposed in any way. But some other application somehow ends up connected to the database and that kicks my connection out.

When I run sp_who, I could see that a process that took control of the database is Command="TASK MANAGER".

Anyone could tell me what is this process, what is it's purpose, and how in the world it could get into a database, which is in single-user mode, and there is an active connection?

Had the same issue today, If you have not put your AUTO_UPDATE_STATISTICS ASYNC OFF, you will not be able to enter your database, you can solve this by putting your database offline. Important to know is that you need to set your deadlock priority to high, otherwise you will be deadlocked out of the command. Use following commands to get out of SINGLE user mode

SET DEADLOCK_PRIORITY HIGH

ALTER DATABASE [YourDBName] SET OFFLINE WITH ROLLBACK IMMEDIATE

Followed by

SET DEADLOCK_PRIORITY HIGH

ALTER DATABASE [YourDBName] SET ONLINE WITH ROLLBACK IMMEDIATE

Followed by

SET DEADLOCK_PRIORITY HIGH

ALTER DATABASE [YourDBName] SET MULTI_USER WITH ROLLBACK IMMEDIATE

StackExchange Database Administrators Q#20714, answer score: 10