Re: [PATCH 5/6] nvme-rdma: fix timeout handler

[Chao Leng <lengchao@huawei.com>]

On 2020/8/3 23:03, Sagi Grimberg wrote:
> 
>>> @@ -1946,6 +1947,22 @@ static int nvme_rdma_cm_handler(struct rdma_cm_id *cm_id,
>>>       return 0;
>>>   }
>>> +static void nvme_rdma_complete_timed_out(struct request *rq)
>>> +{
>>> +    struct nvme_rdma_request *req = blk_mq_rq_to_pdu(rq);
>>> +    struct nvme_rdma_queue *queue = req->queue;
>>> +    struct nvme_rdma_ctrl *ctrl = queue->ctrl;
>>> +
>>> +    /* fence other contexts that may complete the command */
>>> +    flush_work(&ctrl->err_work);
>>> +    nvme_rdma_stop_queue(queue);
>> There maybe concurrent with error recovery, may cause abnormal because
>> nvme_rdma_stop_queue will return but the queue is not stoped,
>> maybe is stopping by the error recovery.
> 
> err_work flush used to fence, once we did queue stop, it should be safe
> to complete the command from the timeout handler.

Flush work just can avoid trigger error recovery by nvme_rdma_timeout or
reduce concurrent probalibity trigger error recovery by other progress,
but can not avoid. if nvme_rdma_cm_handler or other progress call
nvme_rdma_error_recovery, between change state to queue_work may
interrupt by hard interrupt, and then timeout happen, thus flush work
can not avoid concurrent.
Like this:

static void nvme_rdma_error_recovery(struct nvme_rdma_ctrl *ctrl)
{
	if (!nvme_change_ctrl_state(&ctrl->ctrl, NVME_CTRL_RESETTING))
		return;
--------------------------------
may interrupt by hard interrupt, and then timeout progress flush work
at this time. Thus error recovery and nvme_rdma_complete_timed_out may
concurrent to stop queue. will cause: error recovery may cancel request
or nvme_rdma_complete_timed_out may complete request, but the queue may
not be stoped. Thus will cause abnormal.
--------------------------------
	queue_work(nvme_reset_wq, &ctrl->err_work);
}

Another, although the probability of occurrence is very low, reset work
and nvme_rdma_complete_timed_out may also concurrent to stop queue, may
also cause abnormal.

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