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.
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