Messages in this thread | | | Subject | Re: [PATCH 3/9] IB: add a helper to safely drain a QP | From | Steve Wise <> | Date | Mon, 16 Nov 2015 10:38:19 -0600 |
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On 11/15/2015 3:34 AM, Sagi Grimberg wrote: > >> + >> +struct ib_stop_cqe { >> + struct ib_cqe cqe; >> + struct completion done; >> +}; >> + >> +static void ib_stop_done(struct ib_cq *cq, struct ib_wc *wc) >> +{ >> + struct ib_stop_cqe *stop = >> + container_of(wc->wr_cqe, struct ib_stop_cqe, cqe); >> + >> + complete(&stop->done); >> +} >> + >> +/* >> + * Change a queue pair into the error state and wait until all receive >> + * completions have been processed before destroying it. This avoids >> that >> + * the receive completion handler can access the queue pair while it is >> + * being destroyed. >> + */ >> +void ib_drain_qp(struct ib_qp *qp) >> +{ >> + struct ib_qp_attr attr = { .qp_state = IB_QPS_ERR }; >> + struct ib_stop_cqe stop = { }; >> + struct ib_recv_wr wr, *bad_wr; >> + int ret; >> + >> + wr.wr_cqe = &stop.cqe; >> + stop.cqe.done = ib_stop_done; >> + init_completion(&stop.done); >> + >> + ret = ib_modify_qp(qp, &attr, IB_QP_STATE); >> + if (ret) { >> + WARN_ONCE(ret, "failed to drain QP: %d\n", ret); >> + return; >> + } >> + >> + ret = ib_post_recv(qp, &wr, &bad_wr); >> + if (ret) { >> + WARN_ONCE(ret, "failed to drain QP: %d\n", ret); >> + return; >> + } >> + >> + wait_for_completion(&stop.done); >> +} > > This is taken from srp, and srp drains using a recv wr due to a race > causing a use-after-free condition in srp which re-posts a recv buffer > in the recv completion handler. srp does not really care if there are > pending send flushes. > > I'm not sure if there are ordering rules for send/recv queues in > terms of flush completions, meaning that even if all recv flushes > were consumed maybe there are send flushes still pending. > > I think that for a general drain helper it would be useful to > make sure that both the recv _and_ send flushes were drained. > > So, something like: > > void ib_drain_qp(struct ib_qp *qp) > { > struct ib_qp_attr attr = { .qp_state = IB_QPS_ERR }; > struct ib_stop_cqe rstop, sstop; > struct ib_recv_wr rwr = {}, *bad_rwr; > struct ib_send_wr swr = {}, *bad_swr; > int ret; > > rwr.wr_cqe = &rstop.cqe; > rstop.cqe.done = ib_stop_done; > init_completion(&rstop.done); > > swr.wr_cqe = &sstop.cqe; > sstop.cqe.done = ib_stop_done; > init_completion(&sstop.done); > > ret = ib_modify_qp(qp, &attr, IB_QP_STATE); > if (ret) { > WARN_ONCE(ret, "failed to drain QP: %d\n", ret); > return; > } > > ret = ib_post_recv(qp, &rwr, &bad_rwr); > if (ret) { > WARN_ONCE(ret, "failed to drain recv queue: %d\n", ret); > return; > } > > ret = ib_post_send(qp, &swr, &bad_swr); > if (ret) { > WARN_ONCE(ret, "failed to drain send queue: %d\n", ret); > return; > } > > wait_for_completion(&rstop.done); > wait_for_completion(&sstop.done); > } > > Thoughts?
This won't work for iWARP as per my previous email. But I will code something up that will.
Steve
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