IB/ipath: Fix a race condition when generating ACKs

Fix a problem where simple ACKs can be sent ahead of RDMA read
responses thus implicitly NAKing the RDMA read.

Signed-off-by: Ralph Campbell <ralph.cambpell@qlogic.com>
Signed-off-by: Robert Walsh <robert.walsh@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 15 insertions, 13 deletions

diff --git a/drivers/infiniband/hw/ipath/ipath_rc.c b/drivers/infiniband/hw/ipath/ipath_rc.c
index f4d729d5dd1a..1915771fd038 100644
--- a/drivers/infiniband/hw/ipath/ipath_rc.c
+++ b/drivers/infiniband/hw/ipath/ipath_rc.c
@@ -98,13 +98,21 @@ static int ipath_make_rc_ack(struct ipath_qp *qp,
         case OP(RDMA_READ_RESPONSE_LAST):
         case OP(RDMA_READ_RESPONSE_ONLY):
         case OP(ATOMIC_ACKNOWLEDGE):
-                qp->s_ack_state = OP(ACKNOWLEDGE);
+                /*
+                 * We can increment the tail pointer now that the last
+                 * response has been sent instead of only being
+                 * constructed.
+                 */
+                if (++qp->s_tail_ack_queue > IPATH_MAX_RDMA_ATOMIC)
+                        qp->s_tail_ack_queue = 0;
                 /* FALLTHROUGH */
+        case OP(SEND_ONLY):
         case OP(ACKNOWLEDGE):
                 /* Check for no next entry in the queue. */
                 if (qp->r_head_ack_queue == qp->s_tail_ack_queue) {
                         if (qp->s_flags & IPATH_S_ACK_PENDING)
                                 goto normal;
+                        qp->s_ack_state = OP(ACKNOWLEDGE);
                         goto bail;
                 }
 
@@ -117,12 +125,8 @@ static int ipath_make_rc_ack(struct ipath_qp *qp,
                         if (len > pmtu) {
                                 len = pmtu;
                                 qp->s_ack_state = OP(RDMA_READ_RESPONSE_FIRST);
-                        } else {
+                        } else
                                 qp->s_ack_state = OP(RDMA_READ_RESPONSE_ONLY);
-                                if (++qp->s_tail_ack_queue >
-                                    IPATH_MAX_RDMA_ATOMIC)
-                                        qp->s_tail_ack_queue = 0;
-                        }
                         ohdr->u.aeth = ipath_compute_aeth(qp);
                         hwords++;
                         qp->s_ack_rdma_psn = e->psn;
@@ -139,8 +143,6 @@ static int ipath_make_rc_ack(struct ipath_qp *qp,
                                 cpu_to_be32(e->atomic_data);
                         hwords += sizeof(ohdr->u.at) / sizeof(u32);
                         bth2 = e->psn;
-                        if (++qp->s_tail_ack_queue > IPATH_MAX_RDMA_ATOMIC)
-                                qp->s_tail_ack_queue = 0;
                 }
                 bth0 = qp->s_ack_state << 24;
                 break;
@@ -156,8 +158,6 @@ static int ipath_make_rc_ack(struct ipath_qp *qp,
                         ohdr->u.aeth = ipath_compute_aeth(qp);
                         hwords++;
                         qp->s_ack_state = OP(RDMA_READ_RESPONSE_LAST);
-                        if (++qp->s_tail_ack_queue > IPATH_MAX_RDMA_ATOMIC)
-                                qp->s_tail_ack_queue = 0;
                 }
                 bth0 = qp->s_ack_state << 24;
                 bth2 = qp->s_ack_rdma_psn++ & IPATH_PSN_MASK;
@@ -171,7 +171,7 @@ static int ipath_make_rc_ack(struct ipath_qp *qp,
                  * the ACK before setting s_ack_state to ACKNOWLEDGE
                  * (see above).
                  */
-                qp->s_ack_state = OP(ATOMIC_ACKNOWLEDGE);
+                qp->s_ack_state = OP(SEND_ONLY);
                 qp->s_flags &= ~IPATH_S_ACK_PENDING;
                 qp->s_cur_sge = NULL;
                 if (qp->s_nak_state)
@@ -223,7 +223,7 @@ int ipath_make_rc_req(struct ipath_qp *qp,
         /* Sending responses has higher priority over sending requests. */
         if ((qp->r_head_ack_queue != qp->s_tail_ack_queue ||
              (qp->s_flags & IPATH_S_ACK_PENDING) ||
-             qp->s_ack_state != IB_OPCODE_RC_ACKNOWLEDGE) &&
+             qp->s_ack_state != OP(ACKNOWLEDGE)) &&
             ipath_make_rc_ack(qp, ohdr, pmtu, bth0p, bth2p))
                 goto done;
 
@@ -585,7 +585,9 @@ static void send_rc_ack(struct ipath_qp *qp)
         unsigned long flags;
 
         /* Don't send ACK or NAK if a RDMA read or atomic is pending. */
-        if (qp->r_head_ack_queue != qp->s_tail_ack_queue)
+        if (qp->r_head_ack_queue != qp->s_tail_ack_queue ||
+            (qp->s_flags & IPATH_S_ACK_PENDING) ||
+            qp->s_ack_state != OP(ACKNOWLEDGE))
                 goto queue_ack;
 
         /* Construct the header. */