Re: [PATCH 1/2] nvme: pci: simplify timeout handling

Ming Lei
2018-04-26T15:57:24Z

Hi Jianchao,

On Thu, Apr 26, 2018 at 11:07:56PM +0800, jianchao.wang wrote:
> Hi Ming
>
> Thanks for your wonderful solution. :)
>
> On 04/26/2018 08:39 PM, Ming Lei wrote:
> > +/*
> > + * This one is called after queues are quiesced, and no in-fligh timeout
> > + * and nvme interrupt handling.
> > + */
> > +static void nvme_pci_cancel_request(struct request *req, void *data,
> > + bool reserved)
> > +{
> > + /* make sure timed-out requests are covered too */
> > + if (req->rq_flags & RQF_MQ_TIMEOUT_EXPIRED) {
> > + req->aborted_gstate = 0;
> > + req->rq_flags &= ~RQF_MQ_TIMEOUT_EXPIRED;
> > + }
> > +
> > + nvme_cancel_request(req, data, reserved);
> > +}
> > +
> > static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown)
> > {
> > int i;
> > @@ -2223,10 +2316,17 @@ static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown)
> > for (i = dev->ctrl.queue_count - 1; i >= 0; i--)
> > nvme_suspend_queue(&dev->queues[i]);
> >
> > + /*
> > + * safe to sync timeout after queues are quiesced, then all
> > + * requests(include the time-out ones) will be canceled.
> > + */
> > + nvme_sync_queues(&dev->ctrl);
> > + blk_sync_queue(dev->ctrl.admin_q);
> > +
> Looks like blk_sync_queue cannot drain all the timeout work.
>
> blk_sync_queue
> -> del_timer_sync
> blk_mq_timeout_work
> -> mod_timer
> -> cancel_work_sync
> the timeout work may come back again.
> we may need to force all the in-flight requests to be timed out with blk_abort_request
>

blk_abort_request() seems over-kill, we could avoid this race simply by
returning EH_NOT_HANDLED if the controller is in-recovery.

> > nvme_pci_disable(dev);
>
> the interrupt will not come, but there maybe running one.
> a synchronize_sched() here ?

We may cover this case by moving nvme_suspend_queue() before
nvme_stop_queues().

Both two are very good catch, thanks!

--
Ming