I tried twice to get at flushed dmesg output for v3.13, both failed - I
confirmed the hang happens with v3.12 and v3.11 - looks like REISUB does
nothing, no dmesg files were created for the relevant boots...

Shall I set up netconsole and see what I can get?

Just for my education, it looks like dmesg output is part of kern.log
(https://stackoverflow.com/a/11413417/1188444) - is this correct?