Jens Axboe wrote:
Generally the block device rule is that once you are invoked due to an
unplug (or whatever) event, it is the responsibility of the block device
to run the queue until it's done. So if you bail out of queue handling
for whatever reason (might be resource starvation in hard- or software),
you must make sure to reenter queue handling since the device will not
get replugged while it has requests pending. Unless you run into some
software resource shortage, running of the queue is done
deterministically when you know resources are available (ie an io
completes). The device plugging itself is only ever done when you
encounter a shortage outside of your control (memory shortage, for
instance) _and_ you don't already have pending work where you can invoke
queueing from again.
Or he could employ the blk_{start,stop}_queue() functions, if that model
is easier for the driver (and brain).
Jeff
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