This bug started to show up in Xenial with linux-generic-hwe-16.04, and not just linux-generic-hwe-16.04-edge, as the former was updated to version 4.15.0.29.51 in xenial-security:
$ apt-cache policy linux-generic-hwe-16.04 linux-generic-hwe-16.04: Installed: 4.15.0.29.51 Candidate: 4.15.0.29.51 Version table: *** 4.15.0.29.51 500 500 http://ubuntu.trumpetti.atm.tut.fi/ubuntu xenial-updates/main amd64 Packages 100 /var/lib/dpkg/status 4.13.0.45.64 500 500 http://ubuntu.trumpetti.atm.tut.fi/ubuntu xenial-security/main amd64 Packages -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to nvidia-graphics-drivers-304 in Ubuntu. https://bugs.launchpad.net/bugs/1737750 Title: nvidia-graphics-drivers-304 304.137-0ubuntu2 ADT test failure with linux 4.15.0-1.2 [error: implicit declaration of function ‘init_timer’] To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-304/+bug/1737750/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp