dsched_fq and occasional console freeze

[YONETANI Tomokazu <qhwt.dfly@xxxxxxxxxx>]

Hi.
When the current dsched policy is set to fq, the console (or ssh connection)
occasionally freezes (becomes unresponsive, even to ctrl+T).  However,
I can still switch between ttyvN terminals by pressing Alt+Fn keys,
and drop to DDB (I remember reading a similar description in the past,
but I couldn't find the message in my mailbox).

Unfortunately, the kernel dumping locks up too in that case
(no progress is printed on the screen), so no vmcore is available
at the moment.  FWIW, dsched_fq is loaded as kernel module and the policy
is set via /etc/rc.d/sysctl.

This is on an Atom D510 with 4G bytes of RAM and running a very recent
-DEVELOPMENT x86_64 kernel; I haven't tried it on a PC running 32-bit
version yet.