Comment 23 for bug 1546641

One last thing...ice in comment #12 said:
"Some people say it has to do with a ASMedia USB Controller"

Have found that USB enumeration failure can cause a bottleneck in systemd getting the upower.service unit to finally start.

You'll know if the system is hit with this as it'll be much slower to boot and the kernel will spew errors of the type:
kernel: usb 2-1.1: device descriptor read/64, error -110
kernel: usb 2-1-port1: unable to enumerate USB device

Occasionally after several suspend/resumes, I have a USB device (wireless game controller) that must be unplugged/replugged to stop this error (simply rebooting does not fix).

Have found on my laptop, if the USB enumeration boots through without any error then it's quick enough to have systemd start upower.service in time before u-s-d is started, otherwise the u-s-d segfault occurs as above.

Thanks :)