On 2019/11/19 17:43, Zengtao (B) wrote: >> -----Original Message----- >> From: linux-rdma-owner@xxxxxxxxxxxxxxx >> [mailto:linux-rdma-owner@xxxxxxxxxxxxxxx] On Behalf Of Liuyixian (Eason) >> Sent: Tuesday, November 19, 2019 4:00 PM >> To: Jason Gunthorpe >> Cc: dledford@xxxxxxxxxx; leon@xxxxxxxxxx; linux-rdma@xxxxxxxxxxxxxxx; >> Linuxarm >> Subject: Re: [PATCH v2 for-next 1/2] RDMA/hns: Add the workqueue >> framework for flush cqe handler >> >> >> >> On 2019/11/19 1:02, Jason Gunthorpe wrote: >>> On Mon, Nov 18, 2019 at 09:50:24PM +0800, Liuyixian (Eason) wrote: >>>>> It kind of looks like this can be called multiple times? It won't work >>>>> right unless it is called exactly once >>>>> >>>>> Jason >>>> >>>> Yes, you are right. >>>> >>>> So I think the reasonable solution is to allocate it dynamically, and I think >>>> it is a very very little chance that the allocation will be failed. If this >> happened, >>>> I think the application also needs to be over. >>> >>> Why do you need more than one work in parallel for this? Once you >>> start to move the HW to error that only has to happen once, surely? >>> >>> Jason >>> >> The flush operation moves QP, not the HW to error. >> >> For the QP, maybe the process A is posting send while the other >> process B is modifying qp to error, both of these two operation >> needs to initialize one flush work. That's why it could be called >> multiple times. >> >> Furthermore, according to IB protocol 9.9.2.4.2, it may can't stop >> posting wr into the qp even it already transitions to error state. >> That's why it also needs to be called multiple times. >> >> Once the work is implemented successfully, we will free the work, >> it is not a big problem to allocate it dynamically again and again. >> > > So can i understand that this function is designed to be reentrant? > If so, I suggest to introduce a per dev/qp lock to protect. Yes, currently we exactly use the following spinlock per qp to protect the verbs which can be reentrant. spin_lock_irqsave(&qp->sq.lock, flags); > >> Thanks. >> >> >
