-----"Krishnamraju Eraparaju" <krishna2@xxxxxxxxxxx> wrote: ----- >To: "Bernard Metzler" <BMT@xxxxxxxxxxxxxx> >From: "Krishnamraju Eraparaju" <krishna2@xxxxxxxxxxx> >Date: 10/04/2019 06:57AM >Cc: "jgg@xxxxxxxx" <jgg@xxxxxxxx>, "linux-rdma@xxxxxxxxxxxxxxx" ><linux-rdma@xxxxxxxxxxxxxxx>, "Potnuri Bharat Teja" ><bharat@xxxxxxxxxxx>, "Nirranjan Kirubaharan" <nirranjan@xxxxxxxxxxx> >Subject: [EXTERNAL] Re: Re: Re: Re: [PATCH for-next] RDMA/siw: fix >SQ/RQ drain logic to support ib_drain_qp > >On Thursday, October 10/03/19, 2019 at 14:03:05 +0000, Bernard >Metzler wrote: >> There are other reasons why the generic >> __ib_drain_sq() may fail. A CQ overflow is one >> such candidate. Failures are not handled by the ULP, >> since calling a void function. >The function description of ib_drain_qp() says: > * The caller must: > * > * ensure there is room in the CQ(s), SQ, and RQ for drain work >requests > * and completions. > * > * allocate the CQs using ib_alloc_cq(). > * > * ensure that there are no other contexts that are posting WRs > * concurrently. > * Otherwise the drain is not guaranteed. > */ > Yes, I know. Imho, this guarantee falls into the same category as assuming a sane ULP which will not try to change the QP state at the same time while calling for sq_drain. A CQ overflow would be a miscalculation of its size by the ULP. A drain_sq in parallel with a modify_qp call just another misbehaving..? Anyway, I think you are right, let's handle explicitly all cases we can handle. > >So, it looks like ULP has to check for available CQs before calling >ib_drain_xx(). >> >> At the other hand, we know that if we have reached >> ERROR state, the QP will never escape back to become >> full functional; ERROR is the QP's final state. >> >> So we could do an extra check if we cannot get >> the state lock - if we are already in ERROR. And >> if yes, complete immediately there as well. >> >> I can change the patch accordingly. Makes sense? >Yes, I think addressing this would make the fix complete. > sent. I'll be away whole next week from tonight on. Thanks Bernard. >Thanks, >Krishna. > >
