Re: IDE locking problem

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

> > would help making sure we don't get a request sneaking in ?
> 
> Hmm not really, there's still a chance that could happen.

Not too familiar with BIO here, but we would need some kind of
"dead" flag to cause a reject of any try to insert a new request
in the queue, don't you think ?

Then, IDE could do something like:

 - set dead flag
 - wait for all pending requests to drain (easy: insert a barrier
   in the queue and wait on it, with a hack for the barrier insertion
   to bypass the dead flag... ugh... maybe a blk_terminate_queue()
   doing all that would be helpful ?)
 - unregister blkdev
 - then tear down the queue (leaving the "empty" queue with the dead
   flag set, not just memset(...,0,...), so that any bozo keeping a
   reference to it will be rejected trying to insert request instead
   of trying to tap an uninitalized queue object

What do you think ?

Ben.