1 files changed, 197 insertions, 186 deletions

diff --git a/drivers/infiniband/hw/ipath/ipath_rc.c b/drivers/infiniband/hw/ipath/ipath_rc.c
index bd2c405c4bf0..8568dd0538cf 100644
--- a/drivers/infiniband/hw/ipath/ipath_rc.c
+++ b/drivers/infiniband/hw/ipath/ipath_rc.c
@@ -42,7 +42,7 @@
  * @qp: the QP who's SGE we're restarting
  * @wqe: the work queue to initialize the QP's SGE from
  *
- * The QP s_lock should be held.
+ * The QP s_lock should be held and interrupts disabled.
  */
 static void ipath_init_restart(struct ipath_qp *qp, struct ipath_swqe *wqe)
 {
@@ -77,7 +77,6 @@ u32 ipath_make_rc_ack(struct ipath_qp *qp,
                       struct ipath_other_headers *ohdr,
                       u32 pmtu)
 {
-        struct ipath_sge_state *ss;
         u32 hwords;
         u32 len;
         u32 bth0;
@@ -91,7 +90,7 @@ u32 ipath_make_rc_ack(struct ipath_qp *qp,
          */
         switch (qp->s_ack_state) {
         case OP(RDMA_READ_REQUEST):
-                ss = &qp->s_rdma_sge;
+                qp->s_cur_sge = &qp->s_rdma_sge;
                 len = qp->s_rdma_len;
                 if (len > pmtu) {
                         len = pmtu;
@@ -108,7 +107,7 @@ u32 ipath_make_rc_ack(struct ipath_qp *qp,
                 qp->s_ack_state = OP(RDMA_READ_RESPONSE_MIDDLE);
                 /* FALLTHROUGH */
         case OP(RDMA_READ_RESPONSE_MIDDLE):
-                ss = &qp->s_rdma_sge;
+                qp->s_cur_sge = &qp->s_rdma_sge;
                 len = qp->s_rdma_len;
                 if (len > pmtu)
                         len = pmtu;
@@ -127,41 +126,50 @@ u32 ipath_make_rc_ack(struct ipath_qp *qp,
                  * We have to prevent new requests from changing
                  * the r_sge state while a ipath_verbs_send()
                  * is in progress.
-                 * Changing r_state allows the receiver
-                 * to continue processing new packets.
-                 * We do it here now instead of above so
-                 * that we are sure the packet was sent before
-                 * changing the state.
                  */
-                qp->r_state = OP(RDMA_READ_RESPONSE_LAST);
                 qp->s_ack_state = OP(ACKNOWLEDGE);
-                return 0;
+                bth0 = 0;
+                goto bail;
 
         case OP(COMPARE_SWAP):
         case OP(FETCH_ADD):
-                ss = NULL;
+                qp->s_cur_sge = NULL;
                 len = 0;
-                qp->r_state = OP(SEND_LAST);
-                qp->s_ack_state = OP(ACKNOWLEDGE);
-                bth0 = IB_OPCODE_ATOMIC_ACKNOWLEDGE << 24;
+                /*
+                 * Set the s_ack_state so the receive interrupt handler
+                 * won't try to send an ACK (out of order) until this one
+                 * is actually sent.
+                 */
+                qp->s_ack_state = OP(RDMA_READ_RESPONSE_LAST);
+                bth0 = OP(ATOMIC_ACKNOWLEDGE) << 24;
                 ohdr->u.at.aeth = ipath_compute_aeth(qp);
-                ohdr->u.at.atomic_ack_eth = cpu_to_be64(qp->s_ack_atomic);
+                ohdr->u.at.atomic_ack_eth = cpu_to_be64(qp->r_atomic_data);
                 hwords += sizeof(ohdr->u.at) / 4;
                 break;
 
         default:
                 /* Send a regular ACK. */
-                ss = NULL;
+                qp->s_cur_sge = NULL;
                 len = 0;
-                qp->s_ack_state = OP(ACKNOWLEDGE);
-                bth0 = qp->s_ack_state << 24;
-                ohdr->u.aeth = ipath_compute_aeth(qp);
+                /*
+                 * Set the s_ack_state so the receive interrupt handler
+                 * won't try to send an ACK (out of order) until this one
+                 * is actually sent.
+                 */
+                qp->s_ack_state = OP(RDMA_READ_RESPONSE_LAST);
+                bth0 = OP(ACKNOWLEDGE) << 24;
+                if (qp->s_nak_state)
+                        ohdr->u.aeth = cpu_to_be32((qp->r_msn & IPS_MSN_MASK) |
+                                                    (qp->s_nak_state <<
+                                                     IPS_AETH_CREDIT_SHIFT));
+                else
+                        ohdr->u.aeth = ipath_compute_aeth(qp);
                 hwords++;
         }
         qp->s_hdrwords = hwords;
-        qp->s_cur_sge = ss;
         qp->s_cur_size = len;
 
+bail:
         return bth0;
 }
 
@@ -174,7 +182,7 @@ u32 ipath_make_rc_ack(struct ipath_qp *qp,
  * @bth2p: pointer to the BTH PSN word
  *
  * Return 1 if constructed; otherwise, return 0.
- * Note the QP s_lock must be held.
+ * Note the QP s_lock must be held and interrupts disabled.
  */
 int ipath_make_rc_req(struct ipath_qp *qp,
                       struct ipath_other_headers *ohdr,
@@ -356,6 +364,11 @@ int ipath_make_rc_req(struct ipath_qp *qp,
                 bth2 |= qp->s_psn++ & IPS_PSN_MASK;
                 if ((int)(qp->s_psn - qp->s_next_psn) > 0)
                         qp->s_next_psn = qp->s_psn;
+                /*
+                 * Put the QP on the pending list so lost ACKs will cause
+                 * a retry.  More than one request can be pending so the
+                 * QP may already be on the dev->pending list.
+                 */
                 spin_lock(&dev->pending_lock);
                 if (list_empty(&qp->timerwait))
                         list_add_tail(&qp->timerwait,
@@ -365,8 +378,8 @@ int ipath_make_rc_req(struct ipath_qp *qp,
 
         case OP(RDMA_READ_RESPONSE_FIRST):
                 /*
-                 * This case can only happen if a send is restarted.  See
-                 * ipath_restart_rc().
+                 * This case can only happen if a send is restarted.
+                 * See ipath_restart_rc().
                  */
                 ipath_init_restart(qp, wqe);
                 /* FALLTHROUGH */
@@ -526,11 +539,17 @@ static void send_rc_ack(struct ipath_qp *qp)
                 ohdr = &hdr.u.l.oth;
                 lrh0 = IPS_LRH_GRH;
         }
+        /* read pkey_index w/o lock (its atomic) */
         bth0 = ipath_layer_get_pkey(dev->dd, qp->s_pkey_index);
-        ohdr->u.aeth = ipath_compute_aeth(qp);
-        if (qp->s_ack_state >= OP(COMPARE_SWAP)) {
-                bth0 |= IB_OPCODE_ATOMIC_ACKNOWLEDGE << 24;
-                ohdr->u.at.atomic_ack_eth = cpu_to_be64(qp->s_ack_atomic);
+        if (qp->r_nak_state)
+                ohdr->u.aeth = cpu_to_be32((qp->r_msn & IPS_MSN_MASK) |
+                                            (qp->r_nak_state <<
+                                             IPS_AETH_CREDIT_SHIFT));
+        else
+                ohdr->u.aeth = ipath_compute_aeth(qp);
+        if (qp->r_ack_state >= OP(COMPARE_SWAP)) {
+                bth0 |= OP(ATOMIC_ACKNOWLEDGE) << 24;
+                ohdr->u.at.atomic_ack_eth = cpu_to_be64(qp->r_atomic_data);
                 hwords += sizeof(ohdr->u.at.atomic_ack_eth) / 4;
         } else
                 bth0 |= OP(ACKNOWLEDGE) << 24;
@@ -541,15 +560,36 @@ static void send_rc_ack(struct ipath_qp *qp)
         hdr.lrh[3] = cpu_to_be16(ipath_layer_get_lid(dev->dd));
         ohdr->bth[0] = cpu_to_be32(bth0);
         ohdr->bth[1] = cpu_to_be32(qp->remote_qpn);
-        ohdr->bth[2] = cpu_to_be32(qp->s_ack_psn & IPS_PSN_MASK);
+        ohdr->bth[2] = cpu_to_be32(qp->r_ack_psn & IPS_PSN_MASK);
 
         /*
          * If we can send the ACK, clear the ACK state.
          */
         if (ipath_verbs_send(dev->dd, hwords, (u32 *) &hdr, 0, NULL) == 0) {
-                qp->s_ack_state = OP(ACKNOWLEDGE);
-                dev->n_rc_qacks++;
+                qp->r_ack_state = OP(ACKNOWLEDGE);
                 dev->n_unicast_xmit++;
+        } else {
+                /*
+                 * We are out of PIO buffers at the moment.
+                 * Pass responsibility for sending the ACK to the
+                 * send tasklet so that when a PIO buffer becomes
+                 * available, the ACK is sent ahead of other outgoing
+                 * packets.
+                 */
+                dev->n_rc_qacks++;
+                spin_lock_irq(&qp->s_lock);
+                /* Don't coalesce if a RDMA read or atomic is pending. */
+                if (qp->s_ack_state == OP(ACKNOWLEDGE) ||
+                    qp->s_ack_state < OP(RDMA_READ_REQUEST)) {
+                        qp->s_ack_state = qp->r_ack_state;
+                        qp->s_nak_state = qp->r_nak_state;
+                        qp->s_ack_psn = qp->r_ack_psn;
+                        qp->r_ack_state = OP(ACKNOWLEDGE);
+                }
+                spin_unlock_irq(&qp->s_lock);
+
+                /* Call ipath_do_rc_send() in another thread. */
+                tasklet_hi_schedule(&qp->s_task);
         }
 }
 
@@ -641,7 +681,7 @@ done:
  * @psn: packet sequence number for the request
  * @wc: the work completion request
  *
- * The QP s_lock should be held.
+ * The QP s_lock should be held and interrupts disabled.
  */
 void ipath_restart_rc(struct ipath_qp *qp, u32 psn, struct ib_wc *wc)
 {
@@ -705,7 +745,7 @@ bail:
  *
  * This is called from ipath_rc_rcv_resp() to process an incoming RC ACK
  * for the given QP.
- * Called at interrupt level with the QP s_lock held.
+ * Called at interrupt level with the QP s_lock held and interrupts disabled.
  * Returns 1 if OK, 0 if current operation should be aborted (NAK).
  */
 static int do_rc_ack(struct ipath_qp *qp, u32 aeth, u32 psn, int opcode)
@@ -1126,18 +1166,16 @@ static inline int ipath_rc_rcv_error(struct ipath_ibdev *dev,
                  * Don't queue the NAK if a RDMA read, atomic, or
                  * NAK is pending though.
                  */
-                spin_lock(&qp->s_lock);
-                if ((qp->s_ack_state >= OP(RDMA_READ_REQUEST) &&
-                     qp->s_ack_state != IB_OPCODE_ACKNOWLEDGE) ||
-                    qp->s_nak_state != 0) {
-                        spin_unlock(&qp->s_lock);
+                if (qp->s_ack_state != OP(ACKNOWLEDGE) ||
+                    qp->r_nak_state != 0)
                         goto done;
+                if (qp->r_ack_state < OP(COMPARE_SWAP)) {
+                        qp->r_ack_state = OP(SEND_ONLY);
+                        qp->r_nak_state = IB_NAK_PSN_ERROR;
+                        /* Use the expected PSN. */
+                        qp->r_ack_psn = qp->r_psn;
                 }
-                qp->s_ack_state = OP(SEND_ONLY);
-                qp->s_nak_state = IB_NAK_PSN_ERROR;
-                /* Use the expected PSN. */
-                qp->s_ack_psn = qp->r_psn;
-                goto resched;
+                goto send_ack;
         }
 
         /*
@@ -1151,27 +1189,7 @@ static inline int ipath_rc_rcv_error(struct ipath_ibdev *dev,
          * send the earliest so that RDMA reads can be restarted at
          * the requester's expected PSN.
          */
-        spin_lock(&qp->s_lock);
-        if (qp->s_ack_state != IB_OPCODE_ACKNOWLEDGE &&
-            ipath_cmp24(psn, qp->s_ack_psn) >= 0) {
-                if (qp->s_ack_state < IB_OPCODE_RDMA_READ_REQUEST)
-                        qp->s_ack_psn = psn;
-                spin_unlock(&qp->s_lock);
-                goto done;
-        }
-        switch (opcode) {
-        case OP(RDMA_READ_REQUEST):
-                /*
-                 * We have to be careful to not change s_rdma_sge
-                 * while ipath_do_rc_send() is using it and not
-                 * holding the s_lock.
-                 */
-                if (qp->s_ack_state != OP(ACKNOWLEDGE) &&
-                    qp->s_ack_state >= IB_OPCODE_RDMA_READ_REQUEST) {
-                        spin_unlock(&qp->s_lock);
-                        dev->n_rdma_dup_busy++;
-                        goto done;
-                }
+        if (opcode == OP(RDMA_READ_REQUEST)) {
                 /* RETH comes after BTH */
                 if (!header_in_data)
                         reth = &ohdr->u.rc.reth;
@@ -1179,6 +1197,22 @@ static inline int ipath_rc_rcv_error(struct ipath_ibdev *dev,
                         reth = (struct ib_reth *)data;
                         data += sizeof(*reth);
                 }
+                /*
+                 * If we receive a duplicate RDMA request, it means the
+                 * requester saw a sequence error and needs to restart
+                 * from an earlier point.  We can abort the current
+                 * RDMA read send in that case.
+                 */
+                spin_lock_irq(&qp->s_lock);
+                if (qp->s_ack_state != OP(ACKNOWLEDGE) &&
+                    (qp->s_hdrwords || ipath_cmp24(psn, qp->s_ack_psn) >= 0)) {
+                        /*
+                         * We are already sending earlier requested data.
+                         * Don't abort it to send later out of sequence data.
+                         */
+                        spin_unlock_irq(&qp->s_lock);
+                        goto done;
+                }
                 qp->s_rdma_len = be32_to_cpu(reth->length);
                 if (qp->s_rdma_len != 0) {
                         u32 rkey = be32_to_cpu(reth->rkey);
@@ -1192,8 +1226,10 @@ static inline int ipath_rc_rcv_error(struct ipath_ibdev *dev,
                         ok = ipath_rkey_ok(dev, &qp->s_rdma_sge,
                                            qp->s_rdma_len, vaddr, rkey,
                                            IB_ACCESS_REMOTE_READ);
-                        if (unlikely(!ok))
+                        if (unlikely(!ok)) {
+                                spin_unlock_irq(&qp->s_lock);
                                 goto done;
+                        }
                 } else {
                         qp->s_rdma_sge.sg_list = NULL;
                         qp->s_rdma_sge.num_sge = 0;
@@ -1202,25 +1238,44 @@ static inline int ipath_rc_rcv_error(struct ipath_ibdev *dev,
                         qp->s_rdma_sge.sge.length = 0;
                         qp->s_rdma_sge.sge.sge_length = 0;
                 }
-                break;
+                qp->s_ack_state = opcode;
+                qp->s_ack_psn = psn;
+                spin_unlock_irq(&qp->s_lock);
+                tasklet_hi_schedule(&qp->s_task);
+                goto send_ack;
+        }
+
+        /*
+         * A pending RDMA read will ACK anything before it so
+         * ignore earlier duplicate requests.
+         */
+        if (qp->s_ack_state != OP(ACKNOWLEDGE))
+                goto done;
 
+        /*
+         * If an ACK is pending, don't replace the pending ACK
+         * with an earlier one since the later one will ACK the earlier.
+         * Also, if we already have a pending atomic, send it.
+         */
+        if (qp->r_ack_state != OP(ACKNOWLEDGE) &&
+            (ipath_cmp24(psn, qp->r_ack_psn) <= 0 ||
+             qp->r_ack_state >= OP(COMPARE_SWAP)))
+                goto send_ack;
+        switch (opcode) {
         case OP(COMPARE_SWAP):
         case OP(FETCH_ADD):
                 /*
                  * Check for the PSN of the last atomic operation
                  * performed and resend the result if found.
                  */
-                if ((psn & IPS_PSN_MASK) != qp->r_atomic_psn) {
-                        spin_unlock(&qp->s_lock);
+                if ((psn & IPS_PSN_MASK) != qp->r_atomic_psn)
                         goto done;
-                }
-                qp->s_ack_atomic = qp->r_atomic_data;
                 break;
         }
-        qp->s_ack_state = opcode;
-        qp->s_nak_state = 0;
-        qp->s_ack_psn = psn;
-resched:
+        qp->r_ack_state = opcode;
+        qp->r_nak_state = 0;
+        qp->r_ack_psn = psn;
+send_ack:
         return 0;
 
 done:
@@ -1248,7 +1303,6 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
         u32 hdrsize;
         u32 psn;
         u32 pad;
-        unsigned long flags;
         struct ib_wc wc;
         u32 pmtu = ib_mtu_enum_to_int(qp->path_mtu);
         int diff;
@@ -1289,18 +1343,16 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
             opcode <= OP(ATOMIC_ACKNOWLEDGE)) {
                 ipath_rc_rcv_resp(dev, ohdr, data, tlen, qp, opcode, psn,
                                   hdrsize, pmtu, header_in_data);
-                goto bail;
+                goto done;
         }
 
-        spin_lock_irqsave(&qp->r_rq.lock, flags);
-
         /* Compute 24 bits worth of difference. */
         diff = ipath_cmp24(psn, qp->r_psn);
         if (unlikely(diff)) {
                 if (ipath_rc_rcv_error(dev, ohdr, data, qp, opcode,
                                        psn, diff, header_in_data))
                         goto done;
-                goto resched;
+                goto send_ack;
         }
 
         /* Check for opcode sequence errors. */
@@ -1312,22 +1364,19 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
                     opcode == OP(SEND_LAST_WITH_IMMEDIATE))
                         break;
         nack_inv:
-        /*
-         * A NAK will ACK earlier sends and RDMA writes.  Don't queue the
-         * NAK if a RDMA read, atomic, or NAK is pending though.
-         */
-        spin_lock(&qp->s_lock);
-        if (qp->s_ack_state >= OP(RDMA_READ_REQUEST) &&
-            qp->s_ack_state != IB_OPCODE_ACKNOWLEDGE) {
-                spin_unlock(&qp->s_lock);
-                goto done;
-        }
-        /* XXX Flush WQEs */
-        qp->state = IB_QPS_ERR;
-        qp->s_ack_state = OP(SEND_ONLY);
-        qp->s_nak_state = IB_NAK_INVALID_REQUEST;
-        qp->s_ack_psn = qp->r_psn;
-        goto resched;
+                /*
+                 * A NAK will ACK earlier sends and RDMA writes.
+                 * Don't queue the NAK if a RDMA read, atomic, or NAK
+                 * is pending though.
+                 */
+                if (qp->r_ack_state >= OP(COMPARE_SWAP))
+                        goto send_ack;
+                /* XXX Flush WQEs */
+                qp->state = IB_QPS_ERR;
+                qp->r_ack_state = OP(SEND_ONLY);
+                qp->r_nak_state = IB_NAK_INVALID_REQUEST;
+                qp->r_ack_psn = qp->r_psn;
+                goto send_ack;
 
         case OP(RDMA_WRITE_FIRST):
         case OP(RDMA_WRITE_MIDDLE):
@@ -1337,20 +1386,6 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
                         break;
                 goto nack_inv;
 
-        case OP(RDMA_READ_REQUEST):
-        case OP(COMPARE_SWAP):
-        case OP(FETCH_ADD):
-                /*
-                 * Drop all new requests until a response has been sent.  A
-                 * new request then ACKs the RDMA response we sent.  Relaxed
-                 * ordering would allow new requests to be processed but we
-                 * would need to keep a queue of rwqe's for all that are in
-                 * progress.  Note that we can't RNR NAK this request since
-                 * the RDMA READ or atomic response is already queued to be
-                 * sent (unless we implement a response send queue).
-                 */
-                goto done;
-
         default:
                 if (opcode == OP(SEND_MIDDLE) ||
                     opcode == OP(SEND_LAST) ||
@@ -1359,6 +1394,11 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
                     opcode == OP(RDMA_WRITE_LAST) ||
                     opcode == OP(RDMA_WRITE_LAST_WITH_IMMEDIATE))
                         goto nack_inv;
+                /*
+                 * Note that it is up to the requester to not send a new
+                 * RDMA read or atomic operation before receiving an ACK
+                 * for the previous operation.
+                 */
                 break;
         }
 
@@ -1375,17 +1415,12 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
                          * Don't queue the NAK if a RDMA read or atomic
                          * is pending though.
                          */
-                        spin_lock(&qp->s_lock);
-                        if (qp->s_ack_state >=
-                            OP(RDMA_READ_REQUEST) &&
-                            qp->s_ack_state != IB_OPCODE_ACKNOWLEDGE) {
-                                spin_unlock(&qp->s_lock);
-                                goto done;
-                        }
-                        qp->s_ack_state = OP(SEND_ONLY);
-                        qp->s_nak_state = IB_RNR_NAK | qp->s_min_rnr_timer;
-                        qp->s_ack_psn = qp->r_psn;
-                        goto resched;
+                        if (qp->r_ack_state >= OP(COMPARE_SWAP))
+                                goto send_ack;
+                        qp->r_ack_state = OP(SEND_ONLY);
+                        qp->r_nak_state = IB_RNR_NAK | qp->r_min_rnr_timer;
+                        qp->r_ack_psn = qp->r_psn;
+                        goto send_ack;
                 }
                 qp->r_rcv_len = 0;
                 /* FALLTHROUGH */
@@ -1442,7 +1477,7 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
                 if (unlikely(wc.byte_len > qp->r_len))
                         goto nack_inv;
                 ipath_copy_sge(&qp->r_sge, data, tlen);
-                atomic_inc(&qp->msn);
+                qp->r_msn++;
                 if (opcode == OP(RDMA_WRITE_LAST) ||
                     opcode == OP(RDMA_WRITE_ONLY))
                         break;
@@ -1486,29 +1521,8 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
                         ok = ipath_rkey_ok(dev, &qp->r_sge,
                                            qp->r_len, vaddr, rkey,
                                            IB_ACCESS_REMOTE_WRITE);
-                        if (unlikely(!ok)) {
-                        nack_acc:
-                                /*
-                                 * A NAK will ACK earlier sends and RDMA
-                                 * writes.  Don't queue the NAK if a RDMA
-                                 * read, atomic, or NAK is pending though.
-                                 */
-                                spin_lock(&qp->s_lock);
-                                if (qp->s_ack_state >=
-                                    OP(RDMA_READ_REQUEST) &&
-                                    qp->s_ack_state !=
-                                    IB_OPCODE_ACKNOWLEDGE) {
-                                        spin_unlock(&qp->s_lock);
-                                        goto done;
-                                }
-                                /* XXX Flush WQEs */
-                                qp->state = IB_QPS_ERR;
-                                qp->s_ack_state = OP(RDMA_WRITE_ONLY);
-                                qp->s_nak_state =
-                                        IB_NAK_REMOTE_ACCESS_ERROR;
-                                qp->s_ack_psn = qp->r_psn;
-                                goto resched;
-                        }
+                        if (unlikely(!ok))
+                                goto nack_acc;
                 } else {
                         qp->r_sge.sg_list = NULL;
                         qp->r_sge.sge.mr = NULL;
@@ -1535,12 +1549,10 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
                         reth = (struct ib_reth *)data;
                         data += sizeof(*reth);
                 }
-                spin_lock(&qp->s_lock);
-                if (qp->s_ack_state != OP(ACKNOWLEDGE) &&
-                    qp->s_ack_state >= IB_OPCODE_RDMA_READ_REQUEST) {
-                        spin_unlock(&qp->s_lock);
-                        goto done;
-                }
+                if (unlikely(!(qp->qp_access_flags &
+                               IB_ACCESS_REMOTE_READ)))
+                        goto nack_acc;
+                spin_lock_irq(&qp->s_lock);
                 qp->s_rdma_len = be32_to_cpu(reth->length);
                 if (qp->s_rdma_len != 0) {
                         u32 rkey = be32_to_cpu(reth->rkey);
@@ -1552,7 +1564,7 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
                                            qp->s_rdma_len, vaddr, rkey,
                                            IB_ACCESS_REMOTE_READ);
                         if (unlikely(!ok)) {
-                                spin_unlock(&qp->s_lock);
+                                spin_unlock_irq(&qp->s_lock);
                                 goto nack_acc;
                         }
                         /*
@@ -1569,21 +1581,25 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
                         qp->s_rdma_sge.sge.length = 0;
                         qp->s_rdma_sge.sge.sge_length = 0;
                 }
-                if (unlikely(!(qp->qp_access_flags &
-                               IB_ACCESS_REMOTE_READ)))
-                        goto nack_acc;
                 /*
                  * We need to increment the MSN here instead of when we
                  * finish sending the result since a duplicate request would
                  * increment it more than once.
                  */
-                atomic_inc(&qp->msn);
+                qp->r_msn++;
+
                 qp->s_ack_state = opcode;
-                qp->s_nak_state = 0;
                 qp->s_ack_psn = psn;
+                spin_unlock_irq(&qp->s_lock);
+
                 qp->r_psn++;
                 qp->r_state = opcode;
-                goto rdmadone;
+                qp->r_nak_state = 0;
+
+                /* Call ipath_do_rc_send() in another thread. */
+                tasklet_hi_schedule(&qp->s_task);
+
+                goto done;
 
         case OP(COMPARE_SWAP):
         case OP(FETCH_ADD): {
@@ -1612,7 +1628,7 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
                         goto nack_acc;
                 /* Perform atomic OP and save result. */
                 sdata = be64_to_cpu(ateth->swap_data);
-                spin_lock(&dev->pending_lock);
+                spin_lock_irq(&dev->pending_lock);
                 qp->r_atomic_data = *(u64 *) qp->r_sge.sge.vaddr;
                 if (opcode == OP(FETCH_ADD))
                         *(u64 *) qp->r_sge.sge.vaddr =
@@ -1620,8 +1636,8 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
                 else if (qp->r_atomic_data ==
                          be64_to_cpu(ateth->compare_data))
                         *(u64 *) qp->r_sge.sge.vaddr = sdata;
-                spin_unlock(&dev->pending_lock);
-                atomic_inc(&qp->msn);
+                spin_unlock_irq(&dev->pending_lock);
+                qp->r_msn++;
                 qp->r_atomic_psn = psn & IPS_PSN_MASK;
                 psn |= 1 << 31;
                 break;
@@ -1633,44 +1649,39 @@ void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
         }
         qp->r_psn++;
         qp->r_state = opcode;
+        qp->r_nak_state = 0;
         /* Send an ACK if requested or required. */
         if (psn & (1 << 31)) {
                 /*
                  * Coalesce ACKs unless there is a RDMA READ or
                  * ATOMIC pending.
                  */
-                spin_lock(&qp->s_lock);
-                if (qp->s_ack_state == OP(ACKNOWLEDGE) ||
-                    qp->s_ack_state < IB_OPCODE_RDMA_READ_REQUEST) {
-                        qp->s_ack_state = opcode;
-                        qp->s_nak_state = 0;
-                        qp->s_ack_psn = psn;
-                        qp->s_ack_atomic = qp->r_atomic_data;
-                        goto resched;
+                if (qp->r_ack_state < OP(COMPARE_SWAP)) {
+                        qp->r_ack_state = opcode;
+                        qp->r_ack_psn = psn;
                 }
-                spin_unlock(&qp->s_lock);
+                goto send_ack;
         }
-done:
-        spin_unlock_irqrestore(&qp->r_rq.lock, flags);
-        goto bail;
+        goto done;
 
-resched:
+nack_acc:
         /*
-         * Try to send ACK right away but not if ipath_do_rc_send() is
-         * active.
+         * A NAK will ACK earlier sends and RDMA writes.
+         * Don't queue the NAK if a RDMA read, atomic, or NAK
+         * is pending though.
          */
-        if (qp->s_hdrwords == 0 &&
-            (qp->s_ack_state < IB_OPCODE_RDMA_READ_REQUEST ||
-             qp->s_ack_state >= IB_OPCODE_COMPARE_SWAP))
+        if (qp->r_ack_state < OP(COMPARE_SWAP)) {
+                /* XXX Flush WQEs */
+                qp->state = IB_QPS_ERR;
+                qp->r_ack_state = OP(RDMA_WRITE_ONLY);
+                qp->r_nak_state = IB_NAK_REMOTE_ACCESS_ERROR;
+                qp->r_ack_psn = qp->r_psn;
+        }
+send_ack:
+        /* Send ACK right away unless the send tasklet has a pending ACK. */
+        if (qp->s_ack_state == OP(ACKNOWLEDGE))
                 send_rc_ack(qp);
 
-rdmadone:
-        spin_unlock(&qp->s_lock);
-        spin_unlock_irqrestore(&qp->r_rq.lock, flags);
-
-        /* Call ipath_do_rc_send() in another thread. */
-        tasklet_hi_schedule(&qp->s_task);
-
-bail:
+done:
         return;
 }