REISUB required on resume after suspend kernel regression > 3.11

[bruno]

System:
Ubuntu 14.04 64 bit (actually mint 17.1 xfce cinnamon or zorin 9) or Ubuntu 12.04 with trusty-lts kernel
Nvidia proprietary driver (tested with 304, 331 and 346 versions) Geforce GT430
(may be related to nvidia but no bug on another system with Geforce 9400M)

Expected behaviour:
This system suspends/resumes very well on Ubuntu 12.04 with stock kernel (3.2)

What happened instead:
Unusable desktop after resume, nothing can be launched (often black desktop and/or dead mouse). The exact behaviour depends on the kernel version and is not always the same. Sometimes, the desktop is restored (after CTRL-ALT-F8) with a live mouse pointer, but even in these case, nothing can be launched (file not found errors or vanishing desktop after a click or simply no action). Sometimes, (with CTRL-ALT-F1), ext4-fs errors are reported.

Investigation:
All these tests are done on an external usb disk installation, but the exact same configuration is ok with Ubuntu 12.04. I tried usbcore.autosuspend=-1 kernel option at boot without success.
The bug can be reproduced if I update the kernel from a fresh (and functional) 12.04 install. Even on Manjaro, the bug appears with (at least) kernel 3.12.36-1 and 3.16.7.4-1 (but not with 3.10). I tried various kernels/nvidia combinations on 14.04 without any success (3.13/3.16). It seems I can't get trace in log files after suspend.

The bug is similar to https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-331/+bug/1210077. However, 1210077 is supposed to be fixed so this one is different.

[bruno (brunob)]

Moved the hard disk inside the PC case (it was a standard hard disk plugged in a USB mobile disk enclosure) and suspend/resume is ok.

So there is a bug (kernel regression), but only if the OS is installed on an external hard disk.