How to apply changes of `nsswitch.conf` to Cygwin?

The /etc/nsswitch.conf file is read exactly once by the first process of a Cygwin process tree.
If there was no /etc/nsswitch.conf file when this first process started, then no other process in the running Cygwin process tree will try to read the file.

If you create or change /etc/nsswitch.conf, you have to restart all Cygwin processes that need to see the change.
If the process you want to see the change is a child of another process, you need to restart all of that process's parents, too.

How to restart all Cygwin processes?