On Tue, Nov 05, 2019 at 10:06:20AM +0800, Liuyixian (Eason) wrote: > > > 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 . Hi, I'm confident that Doug and/or Jason will review it very soon. Thanks > > Thanks. > > > >
