Disclaimer: not a systemd maintainer.
> 2.) A.)
Unfortunately, backtrace without symbol information is not exactly
useful, especially since introduction of ASLR. If you kept core, please
install systemd-dbg/-dbgsym package and redo gdb backtrace.
> If I understand correctly Lennart might look into this when version
4.5 of the kernel is out[1].
Unless you use systemd.unified_cgroup_hierarchy=1, this is *NOT* your
issue (some symptoms maybe /looks/ similar, but effects in 2.B.,.C,.D,.E
are exactly same in about /any/ systemd crash), and Lennart note about
4.5 kernel does not apply to you.
P.S. I might note that the way systemd handles crashes is not quite
suitable for any production system :-|
Considering complexity (and likelihood of bugs), it should do something
less drastic.
