Larry Finger discovered a weird behavior under load.
In essence, the queue's length count under runs,
which in turn renders the associated ac queue unusable.
Reported-by: NLarry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: NChristian Lamparter <chunkeey@web.de>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>