Facing permanent hangs on /restart (or via update center).
"Please wait while Jenkins is restarting..."
The error log shows only these two rows at the time of restart and no further logging once it hangs.
Jul 25, 2014 1:02:50 PM jenkins.model.Jenkins$24 run
INFO: Restart in 10 seconds
Jul 25, 2014 1:03:00 PM jenkins.model.Jenkins$24 run
SEVERE: Restarting VM as requested by anonymous
Reported by a few users at the following link, one user posted a thread dump from the java process after hanging occurs.