After latest update (29 March), my laptop which runs Fedora 21 could’t resume from hibernation. I can’t determine which update broke the system, but usually the first suspect is the kernel. Reverting to older kernels doesn’t fix the problem, so I guess there are other factors in play.
After some detective work I could see that the system failed to read hibernation image when resuming. My first guess that there was something wrong with swap partition, but it seemed OK.
Further Googling and reading about how to enable hibernation on Linux suggested me the following solution: GRUB should inform the Linux kernel where to find hibernation image (i.e. the swap partition).
That should be straightforward: edit /etc/default/grub, add the following line:
where 6fffdb46-0e7c-4fee-ace4-75cdb30fad5c is the uuid of my swap partition (yours should be different). Next step is to run grub-mkconfig (grub2-mkconfig on Fedora 21):
grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg
Reboot, and hibernation works again. I still don’t know how the update broke it in the first place though.