This works fine on Debian and Fedora, with the same udev upstream version. I verified that the hang still happens with Debian's kernel or Debian's udev+libudev1 packages. If I install just the systemd binary package from Debian, the hang goes away. More specifically, installing Debian's /lib/systemd/systemd as /lib/systemd/systemd-debian and booting that (with init) also makes the bug go away. So something in our Ubuntu patches causes this.
This works fine on Debian and Fedora, with the same udev upstream version. I verified that the hang still happens with Debian's kernel or Debian's udev+libudev1 packages. If I install just the systemd binary package from Debian, the hang goes away. More specifically, installing Debian's /lib/systemd/ systemd as /lib/systemd/ systemd- debian and booting that (with init) also makes the bug go away. So something in our Ubuntu patches causes this.