+
+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?
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