systemd-journald flush hangs system

[Ralf Corsepius]

Hi,

I am facing a weird issue on an f20 test system:

During a yum update in an attempt to update this machine from the status 
ca. a week ago to today's, a message appears:

# yum update
...
"systemd-journald[...]: Received request to flush runtime journal from 
PID 1"
[hangs]

After this message, the system appears to be hung and non-responsive.
The yum process hangs, Ctl-Alt-F<X> doesn't work, no visible disk activity.

However, pressing the power-off button seems to trigger a proper 
systemd-controlled shutdown.

What is going on?

Ralf