lockdep WARNING at blktests block/011

[Keith Busch]

On Mon, Oct 03, 2022 at 01:32:41PM +0000, Shinichiro Kawasaki wrote:
> 
> BTW, I came up to another question during code read. I found nvme_reset_work()
> calls nvme_dev_disable() before nvme_sync_queues(). So, I think the NVME
> controller is already disabled when the reset work calls nvme_sync_queues().

Right, everything previously outstanding has been reclaimed, and the queues are
quiesced at this point. There's nothing for timeout work to wait for, and the
sync is just ensuring every timeout work has returned.

It looks like a timeout is required in order to hit this reported deadlock, but
the driver ensures there's nothing to timeout prior to syncing the queues. I
don't think lockdep could reasonably know that, though.