On 3/18/2019 6:31 PM, Ming Lei wrote:
On Mon, Mar 18, 2019 at 10:37:08AM -0700, James Smart wrote:
On 3/17/2019 8:29 PM, Ming Lei wrote:
In NVMe's error handler, follows the typical steps for tearing down
hardware:
1) stop blk_mq hw queues
2) stop the real hw queues
3) cancel in-flight requests via
blk_mq_tagset_busy_iter(tags, cancel_request, ...)
cancel_request():
mark the request as abort
blk_mq_complete_request(req);
4) destroy real hw queues
However, there may be race between #3 and #4, because blk_mq_complete_request()
actually completes the request asynchronously.
This patch introduces blk_mq_complete_request_sync() for fixing the
above race.
This won't help FC at all. Inherently, the "completion" has to be
asynchronous as line traffic may be required.
e.g. FC doesn't use nvme_complete_request() in the iterator routine.
Looks FC has done the sync already, see nvme_fc_delete_association():
...
/* wait for all io that had to be aborted */
spin_lock_irq(&ctrl->lock);
wait_event_lock_irq(ctrl->ioabort_wait, ctrl->iocnt == 0, ctrl->lock);
ctrl->flags &= ~FCCTRL_TERMIO;
spin_unlock_irq(&ctrl->lock);
yes - but the iterator started a lot of the back end io terminating in
parallel. So waiting on many happening in parallel is better than
waiting 1 at a time. Even so, I've always disliked this wait and would
have preferred to exit the thread with something monitoring the
completions re-queuing a work thread to finish.
-- james
