On 2019/10/28 17:34, Liuyixian (Eason) wrote: > > > On 2019/10/15 16:00, Leon Romanovsky wrote: >> On Sat, Oct 12, 2019 at 11:53:36AM +0800, Liuyixian (Eason) wrote: >>> >>> >>> On 2019/9/24 11:54, Liuyixian (Eason) wrote: >>>> >>>> >>>> On 2019/9/23 13:01, Leon Romanovsky wrote: >>>>> On Fri, Sep 20, 2019 at 11:55:56AM +0800, Liuyixian (Eason) wrote: >>>>>> >>>>>> >>>>>> On 2019/9/11 21:17, Liuyixian (Eason) wrote: >>>>>>> >>>>>>> >>>>>>> On 2019/9/10 15:52, Leon Romanovsky wrote: >>>>>>>> On Tue, Sep 10, 2019 at 02:40:20PM +0800, Liuyixian (Eason) wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>> On 2019/9/8 16:03, Leon Romanovsky wrote: >>>>>>>>>> On Thu, Sep 05, 2019 at 08:31:11PM +0800, Weihang Li wrote: >>>>>>>>>>> From: Yixian Liu <liuyixian@xxxxxxxxxx> >>>>>>>>>>> >>>>>>>>>>> Hip08 has the feature flush cqe, which help to flush wqe in workqueue >>>>>>>>>>> (sq and rq) when error happened by transmitting producer index with >>>>>>>>>>> mailbox to hardware. Flush cqe is emplemented in post send and recv >>>>>>>>>>> verbs. However, under NVMe cases, these verbs will be called under >>>>>>>>>>> softirq context, and it will lead to following calltrace with >>>>>>>>>>> current driver as mailbox used by flush cqe can go to sleep. >>>>>>>>>>> >>>>>>>>>>> This patch solves this problem by using workqueue to do flush cqe, >>>>>>>>>> >>>>>>>>>> Unbelievable, almost every bug in this driver is solved by introducing >>>>>>>>>> workqueue. You should fix "sleep in flush path" issue and not by adding >>>>>>>>>> new workqueue. >>>>>>>>>> >>>>>>>>> Hi Leon, >>>>>>>>> >>>>>>>>> Thanks for the comment. >>>>>>>>> Up to now, for hip08, only one place use workqueue in hns_roce_hw_v2.c >>>>>>>>> where for irq prints. >>>>>>>> >>>>>>>> Thanks to our lack of desire to add more workqueues and previous patches >>>>>>>> which removed extra workqueues from the driver. >>>>>>>> >>>>>>> Thanks, I see. >>>>>>> >>>>>>>>> >>>>>>>>> The solution for flush cqe in this patch is as follow: >>>>>>>>> While flush cqe should be implement, the driver should modify qp to error state >>>>>>>>> through mailbox with the newest product index of sq and rq, the hardware then >>>>>>>>> can flush all outstanding wqes in sq and rq. >>>>>>>>> >>>>>>>>> That's the whole mechanism of flush cqe, also is the flush path. We can't >>>>>>>>> change neither mailbox sleep attribute or flush cqe occurred in post send/recv. >>>>>>>>> To avoid the calltrace of flush cqe in post verbs under NVMe softirq, >>>>>>>>> use workqueue for flush cqe seems reasonable. >>>>>>>>> >>>>>>>>> As far as I know, there is no other alternative solution for this situation. >>>>>>>>> I will be very grateful if you reminder me more information. >>>>>>>> >>>>>>>> ib_drain_rq/ib_drain_sq/ib_drain_qp???? >>>>>>>> >>>>>>> Hi Leon, >>>>>>> >>>>>>> I think these interfaces are designed for application to check that all wqes >>>>>>> have been processed by hardware, so called drain or flush. However, it is not >>>>>>> the same as the flush in this patch. The solution in this patch is used >>>>>>> to help the hardware generate flush cqes for outstanding wqes while qp error. >>>>>>> >>>>>> Hi Leon, >>>>>> >>>>>> What's your opinion about above? Do you have any further comments? >>>>> >>>>> My opinion didn't change, you need to read discussions about ib_drain_*() >>>>> functions, how and why they were introduced. It is a way to go. >>>>> >>>>> Thanks >>>> >>>> Hi Leon, >>>> >>>> Thanks a lot! I will dig those functions for my problem. >>>> >>> >>> Hi Leon, >>> >>> I have analysis the mechanism of ib_drain_(qp, sq, rq), that's okay to use >>> it instead of our flush cqe as both of them are calling modify qp to error >>> state in flush path. >>> >>> However, both ib_drain_* and flush cqe will face the same problem as declared >>> in previous emails, that is, in NVME case, post verbs will be called under >>> **softirq**, which will result to calltrace as mailbox used in modify qp >>> (flush path) can sleep, this is not allowed under softirq. >>> >>> Thus, to resolve above calltrace (sleep in softirq), using workqueue as in >>> this patch seems is a reasonable solution regardless of ib_drain_qp or >>> flush cqe is called in the workqueue. >>> >>> I think it is not a good idea to fix sleep in flush path (actually referred >>> to mailbox used in modify qp) as the mailbox is such a mature mechanism. >> >> No, it is not reasonable solution. >> > > Hi Leon, > > I have explained this issue better in another patch set and pruned other logic. > Thanks a lot for your review! > > Best regards. > Eason > Hi Doug and Loen, I just want to make sure that you know the above mentioned patch set is on: https://patchwork.kernel.org/project/linux-rdma/list/?series=194423 Sorry to reply your last comment so late as I analyzed all possible solutions with your comment, and found that I haven't describe our problem clear enough and accurate, thus, I made this new patch set with simple logic and detailed commit message. I hope I have clearly explained this problem . Thanks.
