nvme/rdma initiator stuck on reboot

[hch@infradead.org ('Christoph Hellwig')]

On Thu, Aug 18, 2016@08:59:15AM -0500, Steve Wise wrote:
> Sure, but let me ask a question:  So the bug was that the delete controller
> worker was blocked waiting for the reconnect worker to complete.

Btw, in that case the patch is not actually correct, as even workqueue
with a higher concurrency level MAY deadlock under enough memory
pressure.  We'll need separate workqueues to handle this case I think.

> Yes?  And the
> reconnect worker was never completing?  Why is that?  Here are a few tidbits
> about iWARP connections:  address resolution == neighbor discovery.  So if the
> neighbor is unreachable, it will take a few seconds for the OS to give up and
> fail the resolution.  If the neigh entry is valid and the peer becomes
> unreachable during connection setup, it might take 60 seconds or so for a
> connect operation to give up and fail.  So this is probably slowing the
> reconnect thread down.   But shouldn't the reconnect thread notice that a delete
> is trying to happen and bail out? 

I think we should aim for a state machine that can detect this, but
we'll have to see if that will end up in synchronization overkill.