Re: [PATCH v5 for-next 1/2] RDMA/hns: Add the workqueue framework for flush cqe handler

[Jason Gunthorpe <jgg@ziepe.ca>]

On Mon, Jan 13, 2020 at 07:26:45PM +0800, Liuyixian (Eason) wrote:
> 
> 
> On 2020/1/10 23:26, Jason Gunthorpe wrote:
> > On Sat, Dec 28, 2019 at 11:28:54AM +0800, Yixian Liu wrote:
> >> +void init_flush_work(struct hns_roce_dev *hr_dev, struct hns_roce_qp *hr_qp)
> >> +{
> >> +	struct hns_roce_work *flush_work;
> >> +
> >> +	flush_work = kzalloc(sizeof(struct hns_roce_work), GFP_ATOMIC);
> >> +	if (!flush_work)
> >> +		return;
> > 
> > You changed it to only queue once, so why do we need the allocation
> > now? That was the whole point..
> 
> Hi Jason,
> 
> The flush work is queued **not only once**. As the flag being_pushed is set to 0 during
> the process of modifying qp like this:
> 	hns_roce_v2_modify_qp {
> 		...
> 		if (new_state == IB_QPS_ERR) {
> 			spin_lock_irqsave(&hr_qp->sq.lock, sq_flag);
> 			...
> 			hr_qp->state = IB_QPS_ERR;
> 			hr_qp->being_push = 0;
> 			...
> 		}
> 		...
> 	}
> which means the new updated PI value needs to be updated with initializing a new flush work.
> Thus, maybe there are two flush work in the workqueue. Thus, we still need the allocation here.

I don't see how you should get two? One should be pending until the
modify is done with the new PI, then once the PI is updated the same
one should be re-queued the next time the PI needs changing.

Jason