I was not able to reproduce following on systemd 216 and unfortunately I don't have a nice stack trace (mips) but...

(gdb) core-file core.systemd.0.e8cd5aaf1d384bbe9467f348cbe044dc.2630.1159241238000000 
[New LWP 2630]
Core was generated by `/usr/lib/systemd/systemd'.
Program terminated with signal 8, Arithmetic exception.
#0  0x77ad4724 in raise (sig=8) at ../nptl/sysdeps/unix/sysv/linux/pt-raise.c:46
46	../nptl/sysdeps/unix/sysv/linux/pt-raise.c: No such file or directory.
(gdb) bt
#0  0x77ad4724 in raise (sig=8) at ../nptl/sysdeps/unix/sysv/linux/pt-raise.c:46
#1  0x00454118 in crash.1663 (sig=8) at /dev/apps/systemd/systemd/src/core/main.c:163
#2  <signal handler called>
#3  0x00a65c88 in ?? ()

Steps to reproduce:

- I am aware that steps taken here don't make sense but still, we shouldn't be able to crash PID 1.

# ln -s /usr/lib/systemd/system/multi-user.target /etc/systemd/system/a-pre.target
# vi /etc/systemd/system/a.target
[Unit]
Description=Starting A
Requires=a-pre.target
Conflicts=rescue.service rescue.target
After=a-pre.target
AllowIsolate=yes

# ln -s ../a-pre.target /etc/systemd/system/multi-user.target.wants
# ln -s ../a.target /etc/systemd/system/multi-user.target.wants
# systemctl daemon-reload
# systemctl -f reboot

Immediately after executing reboot, systemd crashes.