>From: matthew green <mrg@eterna.com.au>
>
>my observance of this bug is that (a) it's been around for a long time,
>and (b) it tends to happen more commonly if the nfs file systems are used
>more often.  eg, a machine freshly booted is rather unlikely to hang in
>shutdown than one that's been up for a month.
>
>"a long time" above means "well over a year."

It may be that it has been around for a long time, but something
happened in the past month or so to make it worse.  My diskless PC
hangs in this way almost every time now.  I did notice that if I mount
an NFS filesystem and immediately dismount it, the system doesn't
hang.  So up to a point my experience agrees wit yours in that it
needs to at least get some usage for the bug to be triggered, but the
amount of use that a system gets while booting to multiuser now seems
to be sufficient.  During my testing in preparing my PR, all I was
doing was booting up the machine, then doing a shutdown -r now or a
shutdown now followed by umount /usr.  No other activity at all, and
the hang occurred every time.

Cheers,
entropy

--
entropy -- it's not just a good idea, it's the second law.