drivers/infiniband/sw/rxe/rxe_comp.c

   1 /*
   2  * Copyright (c) 2016 Mellanox Technologies Ltd. All rights reserved.
   3  * Copyright (c) 2015 System Fabric Works, Inc. All rights reserved.
   4  *
   5  * This software is available to you under a choice of one of two
   6  * licenses.  You may choose to be licensed under the terms of the GNU
   7  * General Public License (GPL) Version 2, available from the file
   8  * COPYING in the main directory of this source tree, or the
   9  * OpenIB.org BSD license below:
  10  *
  11  *     Redistribution and use in source and binary forms, with or
  12  *     without modification, are permitted provided that the following
  13  *     conditions are met:
  14  *
  15  *      - Redistributions of source code must retain the above
  16  *        copyright notice, this list of conditions and the following
  17  *        disclaimer.
  18  *
  19  *      - Redistributions in binary form must reproduce the above
  20  *        copyright notice, this list of conditions and the following
  21  *        disclaimer in the documentation and/or other materials
  22  *        provided with the distribution.
  23  *
  24  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  25  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  26  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  27  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  28  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  29  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  30  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  31  * SOFTWARE.
  32  */
  33
  34 #include <linux/skbuff.h>
  35
  36 #include "rxe.h"
  37 #include "rxe_loc.h"
  38 #include "rxe_queue.h"
  39 #include "rxe_task.h"
  40
  41 enum comp_state {
  42         COMPST_GET_ACK,
  43         COMPST_GET_WQE,
  44         COMPST_COMP_WQE,
  45         COMPST_COMP_ACK,
  46         COMPST_CHECK_PSN,
  47         COMPST_CHECK_ACK,
  48         COMPST_READ,
  49         COMPST_ATOMIC,
  50         COMPST_WRITE_SEND,
  51         COMPST_UPDATE_COMP,
  52         COMPST_ERROR_RETRY,
  53         COMPST_RNR_RETRY,
  54         COMPST_ERROR,
  55         COMPST_EXIT, /* We have an issue, and we want to rerun the completer */
  56         COMPST_DONE, /* The completer finished successflly */
  57 };
  58
  59 static char *comp_state_name[] =  {
  60         [COMPST_GET_ACK]                = "GET ACK",
  61         [COMPST_GET_WQE]                = "GET WQE",
  62         [COMPST_COMP_WQE]               = "COMP WQE",
  63         [COMPST_COMP_ACK]               = "COMP ACK",
  64         [COMPST_CHECK_PSN]              = "CHECK PSN",
  65         [COMPST_CHECK_ACK]              = "CHECK ACK",
  66         [COMPST_READ]                   = "READ",
  67         [COMPST_ATOMIC]                 = "ATOMIC",
  68         [COMPST_WRITE_SEND]             = "WRITE/SEND",
  69         [COMPST_UPDATE_COMP]            = "UPDATE COMP",
  70         [COMPST_ERROR_RETRY]            = "ERROR RETRY",
  71         [COMPST_RNR_RETRY]              = "RNR RETRY",
  72         [COMPST_ERROR]                  = "ERROR",
  73         [COMPST_EXIT]                   = "EXIT",
  74         [COMPST_DONE]                   = "DONE",
  75 };
  76
  77 static unsigned long rnrnak_usec[32] = {
  78         [IB_RNR_TIMER_655_36] = 655360,
  79         [IB_RNR_TIMER_000_01] = 10,
  80         [IB_RNR_TIMER_000_02] = 20,
  81         [IB_RNR_TIMER_000_03] = 30,
  82         [IB_RNR_TIMER_000_04] = 40,
  83         [IB_RNR_TIMER_000_06] = 60,
  84         [IB_RNR_TIMER_000_08] = 80,
  85         [IB_RNR_TIMER_000_12] = 120,
  86         [IB_RNR_TIMER_000_16] = 160,
  87         [IB_RNR_TIMER_000_24] = 240,
  88         [IB_RNR_TIMER_000_32] = 320,
  89         [IB_RNR_TIMER_000_48] = 480,
  90         [IB_RNR_TIMER_000_64] = 640,
  91         [IB_RNR_TIMER_000_96] = 960,
  92         [IB_RNR_TIMER_001_28] = 1280,
  93         [IB_RNR_TIMER_001_92] = 1920,
  94         [IB_RNR_TIMER_002_56] = 2560,
  95         [IB_RNR_TIMER_003_84] = 3840,
  96         [IB_RNR_TIMER_005_12] = 5120,
  97         [IB_RNR_TIMER_007_68] = 7680,
  98         [IB_RNR_TIMER_010_24] = 10240,
  99         [IB_RNR_TIMER_015_36] = 15360,
 100         [IB_RNR_TIMER_020_48] = 20480,
 101         [IB_RNR_TIMER_030_72] = 30720,
 102         [IB_RNR_TIMER_040_96] = 40960,
 103         [IB_RNR_TIMER_061_44] = 61410,
 104         [IB_RNR_TIMER_081_92] = 81920,
 105         [IB_RNR_TIMER_122_88] = 122880,
 106         [IB_RNR_TIMER_163_84] = 163840,
 107         [IB_RNR_TIMER_245_76] = 245760,
 108         [IB_RNR_TIMER_327_68] = 327680,
 109         [IB_RNR_TIMER_491_52] = 491520,
 110 };
 111
 112 static inline unsigned long rnrnak_jiffies(u8 timeout)
 113 {
 114         return max_t(unsigned long,
 115                 usecs_to_jiffies(rnrnak_usec[timeout]), 1);
 116 }
 117
 118 static enum ib_wc_opcode wr_to_wc_opcode(enum ib_wr_opcode opcode)
 119 {
 120         switch (opcode) {
 121         case IB_WR_RDMA_WRITE:                  return IB_WC_RDMA_WRITE;
 122         case IB_WR_RDMA_WRITE_WITH_IMM:         return IB_WC_RDMA_WRITE;
 123         case IB_WR_SEND:                        return IB_WC_SEND;
 124         case IB_WR_SEND_WITH_IMM:               return IB_WC_SEND;
 125         case IB_WR_RDMA_READ:                   return IB_WC_RDMA_READ;
 126         case IB_WR_ATOMIC_CMP_AND_SWP:          return IB_WC_COMP_SWAP;
 127         case IB_WR_ATOMIC_FETCH_AND_ADD:        return IB_WC_FETCH_ADD;
 128         case IB_WR_LSO:                         return IB_WC_LSO;
 129         case IB_WR_SEND_WITH_INV:               return IB_WC_SEND;
 130         case IB_WR_RDMA_READ_WITH_INV:          return IB_WC_RDMA_READ;
 131         case IB_WR_LOCAL_INV:                   return IB_WC_LOCAL_INV;
 132         case IB_WR_REG_MR:                      return IB_WC_REG_MR;
 133
 134         default:
 135                 return 0xff;
 136         }
 137 }
 138
 139 void retransmit_timer(unsigned long data)
 140 {
 141         struct rxe_qp *qp = (struct rxe_qp *)data;
 142
 143         if (qp->valid) {
 144                 qp->comp.timeout = 1;
 145                 rxe_run_task(&qp->comp.task, 1);
 146         }
 147 }
 148
 149 void rxe_comp_queue_pkt(struct rxe_dev *rxe, struct rxe_qp *qp,
 150                         struct sk_buff *skb)
 151 {
 152         int must_sched;
 153
 154         skb_queue_tail(&qp->resp_pkts, skb);
 155
 156         must_sched = skb_queue_len(&qp->resp_pkts) > 1;
 157         rxe_run_task(&qp->comp.task, must_sched);
 158 }
 159
 160 static inline enum comp_state get_wqe(struct rxe_qp *qp,
 161                                       struct rxe_pkt_info *pkt,
 162                                       struct rxe_send_wqe **wqe_p)
 163 {
 164         struct rxe_send_wqe *wqe;
 165
 166         /* we come here whether or not we found a response packet to see if
 167          * there are any posted WQEs
 168          */
 169         wqe = queue_head(qp->sq.queue);
 170         *wqe_p = wqe;
 171
 172         /* no WQE or requester has not started it yet */
 173         if (!wqe || wqe->state == wqe_state_posted)
 174                 return pkt ? COMPST_DONE : COMPST_EXIT;
 175
 176         /* WQE does not require an ack */
 177         if (wqe->state == wqe_state_done)
 178                 return COMPST_COMP_WQE;
 179
 180         /* WQE caused an error */
 181         if (wqe->state == wqe_state_error)
 182                 return COMPST_ERROR;
 183
 184         /* we have a WQE, if we also have an ack check its PSN */
 185         return pkt ? COMPST_CHECK_PSN : COMPST_EXIT;
 186 }
 187
 188 static inline void reset_retry_counters(struct rxe_qp *qp)
 189 {
 190         qp->comp.retry_cnt = qp->attr.retry_cnt;
 191         qp->comp.rnr_retry = qp->attr.rnr_retry;
 192 }
 193
 194 static inline enum comp_state check_psn(struct rxe_qp *qp,
 195                                         struct rxe_pkt_info *pkt,
 196                                         struct rxe_send_wqe *wqe)
 197 {
 198         s32 diff;
 199
 200         /* check to see if response is past the oldest WQE. if it is, complete
 201          * send/write or error read/atomic
 202          */
 203         diff = psn_compare(pkt->psn, wqe->last_psn);
 204         if (diff > 0) {
 205                 if (wqe->state == wqe_state_pending) {
 206                         if (wqe->mask & WR_ATOMIC_OR_READ_MASK)
 207                                 return COMPST_ERROR_RETRY;
 208
 209                         reset_retry_counters(qp);
 210                         return COMPST_COMP_WQE;
 211                 } else {
 212                         return COMPST_DONE;
 213                 }
 214         }
 215
 216         /* compare response packet to expected response */
 217         diff = psn_compare(pkt->psn, qp->comp.psn);
 218         if (diff < 0) {
 219                 /* response is most likely a retried packet if it matches an
 220                  * uncompleted WQE go complete it else ignore it
 221                  */
 222                 if (pkt->psn == wqe->last_psn)
 223                         return COMPST_COMP_ACK;
 224                 else
 225                         return COMPST_DONE;
 226         } else if ((diff > 0) && (wqe->mask & WR_ATOMIC_OR_READ_MASK)) {
 227                 return COMPST_DONE;
 228         } else {
 229                 return COMPST_CHECK_ACK;
 230         }
 231 }
 232
 233 static inline enum comp_state check_ack(struct rxe_qp *qp,
 234                                         struct rxe_pkt_info *pkt,
 235                                         struct rxe_send_wqe *wqe)
 236 {
 237         unsigned int mask = pkt->mask;
 238         u8 syn;
 239
 240         /* Check the sequence only */
 241         switch (qp->comp.opcode) {
 242         case -1:
 243                 /* Will catch all *_ONLY cases. */
 244                 if (!(mask & RXE_START_MASK))
 245                         return COMPST_ERROR;
 246
 247                 break;
 248
 249         case IB_OPCODE_RC_RDMA_READ_RESPONSE_FIRST:
 250         case IB_OPCODE_RC_RDMA_READ_RESPONSE_MIDDLE:
 251                 if (pkt->opcode != IB_OPCODE_RC_RDMA_READ_RESPONSE_MIDDLE &&
 252                     pkt->opcode != IB_OPCODE_RC_RDMA_READ_RESPONSE_LAST) {
 253                         return COMPST_ERROR;
 254                 }
 255                 break;
 256         default:
 257                 WARN_ON_ONCE(1);
 258         }
 259
 260         /* Check operation validity. */
 261         switch (pkt->opcode) {
 262         case IB_OPCODE_RC_RDMA_READ_RESPONSE_FIRST:
 263         case IB_OPCODE_RC_RDMA_READ_RESPONSE_LAST:
 264         case IB_OPCODE_RC_RDMA_READ_RESPONSE_ONLY:
 265                 syn = aeth_syn(pkt);
 266
 267                 if ((syn & AETH_TYPE_MASK) != AETH_ACK)
 268                         return COMPST_ERROR;
 269
 270                 /* Fall through (IB_OPCODE_RC_RDMA_READ_RESPONSE_MIDDLE
 271                  * doesn't have an AETH)
 272                  */
 273         case IB_OPCODE_RC_RDMA_READ_RESPONSE_MIDDLE:
 274                 if (wqe->wr.opcode != IB_WR_RDMA_READ &&
 275                     wqe->wr.opcode != IB_WR_RDMA_READ_WITH_INV) {
 276                         return COMPST_ERROR;
 277                 }
 278                 reset_retry_counters(qp);
 279                 return COMPST_READ;
 280
 281         case IB_OPCODE_RC_ATOMIC_ACKNOWLEDGE:
 282                 syn = aeth_syn(pkt);
 283
 284                 if ((syn & AETH_TYPE_MASK) != AETH_ACK)
 285                         return COMPST_ERROR;
 286
 287                 if (wqe->wr.opcode != IB_WR_ATOMIC_CMP_AND_SWP &&
 288                     wqe->wr.opcode != IB_WR_ATOMIC_FETCH_AND_ADD)
 289                         return COMPST_ERROR;
 290                 reset_retry_counters(qp);
 291                 return COMPST_ATOMIC;
 292
 293         case IB_OPCODE_RC_ACKNOWLEDGE:
 294                 syn = aeth_syn(pkt);
 295                 switch (syn & AETH_TYPE_MASK) {
 296                 case AETH_ACK:
 297                         reset_retry_counters(qp);
 298                         return COMPST_WRITE_SEND;
 299
 300                 case AETH_RNR_NAK:
 301                         return COMPST_RNR_RETRY;
 302
 303                 case AETH_NAK:
 304                         switch (syn) {
 305                         case AETH_NAK_PSN_SEQ_ERROR:
 306                                 /* a nak implicitly acks all packets with psns
 307                                  * before
 308                                  */
 309                                 if (psn_compare(pkt->psn, qp->comp.psn) > 0) {
 310                                         qp->comp.psn = pkt->psn;
 311                                         if (qp->req.wait_psn) {
 312                                                 qp->req.wait_psn = 0;
 313                                                 rxe_run_task(&qp->req.task, 1);
 314                                         }
 315                                 }
 316                                 return COMPST_ERROR_RETRY;
 317
 318                         case AETH_NAK_INVALID_REQ:
 319                                 wqe->status = IB_WC_REM_INV_REQ_ERR;
 320                                 return COMPST_ERROR;
 321
 322                         case AETH_NAK_REM_ACC_ERR:
 323                                 wqe->status = IB_WC_REM_ACCESS_ERR;
 324                                 return COMPST_ERROR;
 325
 326                         case AETH_NAK_REM_OP_ERR:
 327                                 wqe->status = IB_WC_REM_OP_ERR;
 328                                 return COMPST_ERROR;
 329
 330                         default:
 331                                 pr_warn("unexpected nak %x\n", syn);
 332                                 wqe->status = IB_WC_REM_OP_ERR;
 333                                 return COMPST_ERROR;
 334                         }
 335
 336                 default:
 337                         return COMPST_ERROR;
 338                 }
 339                 break;
 340
 341         default:
 342                 pr_warn("unexpected opcode\n");
 343         }
 344
 345         return COMPST_ERROR;
 346 }
 347
 348 static inline enum comp_state do_read(struct rxe_qp *qp,
 349                                       struct rxe_pkt_info *pkt,
 350                                       struct rxe_send_wqe *wqe)
 351 {
 352         struct rxe_dev *rxe = to_rdev(qp->ibqp.device);
 353         int ret;
 354
 355         ret = copy_data(rxe, qp->pd, IB_ACCESS_LOCAL_WRITE,
 356                         &wqe->dma, payload_addr(pkt),
 357                         payload_size(pkt), to_mem_obj, NULL);
 358         if (ret)
 359                 return COMPST_ERROR;
 360
 361         if (wqe->dma.resid == 0 && (pkt->mask & RXE_END_MASK))
 362                 return COMPST_COMP_ACK;
 363         else
 364                 return COMPST_UPDATE_COMP;
 365 }
 366
 367 static inline enum comp_state do_atomic(struct rxe_qp *qp,
 368                                         struct rxe_pkt_info *pkt,
 369                                         struct rxe_send_wqe *wqe)
 370 {
 371         struct rxe_dev *rxe = to_rdev(qp->ibqp.device);
 372         int ret;
 373
 374         u64 atomic_orig = atmack_orig(pkt);
 375
 376         ret = copy_data(rxe, qp->pd, IB_ACCESS_LOCAL_WRITE,
 377                         &wqe->dma, &atomic_orig,
 378                         sizeof(u64), to_mem_obj, NULL);
 379         if (ret)
 380                 return COMPST_ERROR;
 381         else
 382                 return COMPST_COMP_ACK;
 383 }
 384
 385 static void make_send_cqe(struct rxe_qp *qp, struct rxe_send_wqe *wqe,
 386                           struct rxe_cqe *cqe)
 387 {
 388         memset(cqe, 0, sizeof(*cqe));
 389
 390         if (!qp->is_user) {
 391                 struct ib_wc            *wc     = &cqe->ibwc;
 392
 393                 wc->wr_id               = wqe->wr.wr_id;
 394                 wc->status              = wqe->status;
 395                 wc->opcode              = wr_to_wc_opcode(wqe->wr.opcode);
 396                 if (wqe->wr.opcode == IB_WR_RDMA_WRITE_WITH_IMM ||
 397                     wqe->wr.opcode == IB_WR_SEND_WITH_IMM)
 398                         wc->wc_flags = IB_WC_WITH_IMM;
 399                 wc->byte_len            = wqe->dma.length;
 400                 wc->qp                  = &qp->ibqp;
 401         } else {
 402                 struct ib_uverbs_wc     *uwc    = &cqe->uibwc;
 403
 404                 uwc->wr_id              = wqe->wr.wr_id;
 405                 uwc->status             = wqe->status;
 406                 uwc->opcode             = wr_to_wc_opcode(wqe->wr.opcode);
 407                 if (wqe->wr.opcode == IB_WR_RDMA_WRITE_WITH_IMM ||
 408                     wqe->wr.opcode == IB_WR_SEND_WITH_IMM)
 409                         uwc->wc_flags = IB_WC_WITH_IMM;
 410                 uwc->byte_len           = wqe->dma.length;
 411                 uwc->qp_num             = qp->ibqp.qp_num;
 412         }
 413 }
 414
 415 /*
 416  * IBA Spec. Section 10.7.3.1 SIGNALED COMPLETIONS
 417  * ---------8<---------8<-------------
 418  * ...Note that if a completion error occurs, a Work Completion
 419  * will always be generated, even if the signaling
 420  * indicator requests an Unsignaled Completion.
 421  * ---------8<---------8<-------------
 422  */
 423 static void do_complete(struct rxe_qp *qp, struct rxe_send_wqe *wqe)
 424 {
 425         struct rxe_cqe cqe;
 426
 427         if ((qp->sq_sig_type == IB_SIGNAL_ALL_WR) ||
 428             (wqe->wr.send_flags & IB_SEND_SIGNALED) ||
 429             wqe->status != IB_WC_SUCCESS) {
 430                 make_send_cqe(qp, wqe, &cqe);
 431                 advance_consumer(qp->sq.queue);
 432                 rxe_cq_post(qp->scq, &cqe, 0);
 433         } else {
 434                 advance_consumer(qp->sq.queue);
 435         }
 436
 437         /*
 438          * we completed something so let req run again
 439          * if it is trying to fence
 440          */
 441         if (qp->req.wait_fence) {
 442                 qp->req.wait_fence = 0;
 443                 rxe_run_task(&qp->req.task, 1);
 444         }
 445 }
 446
 447 static inline enum comp_state complete_ack(struct rxe_qp *qp,
 448                                            struct rxe_pkt_info *pkt,
 449                                            struct rxe_send_wqe *wqe)
 450 {
 451         unsigned long flags;
 452
 453         if (wqe->has_rd_atomic) {
 454                 wqe->has_rd_atomic = 0;
 455                 atomic_inc(&qp->req.rd_atomic);
 456                 if (qp->req.need_rd_atomic) {
 457                         qp->comp.timeout_retry = 0;
 458                         qp->req.need_rd_atomic = 0;
 459                         rxe_run_task(&qp->req.task, 1);
 460                 }
 461         }
 462
 463         if (unlikely(qp->req.state == QP_STATE_DRAIN)) {
 464                 /* state_lock used by requester & completer */
 465                 spin_lock_irqsave(&qp->state_lock, flags);
 466                 if ((qp->req.state == QP_STATE_DRAIN) &&
 467                     (qp->comp.psn == qp->req.psn)) {
 468                         qp->req.state = QP_STATE_DRAINED;
 469                         spin_unlock_irqrestore(&qp->state_lock, flags);
 470
 471                         if (qp->ibqp.event_handler) {
 472                                 struct ib_event ev;
 473
 474                                 ev.device = qp->ibqp.device;
 475                                 ev.element.qp = &qp->ibqp;
 476                                 ev.event = IB_EVENT_SQ_DRAINED;
 477                                 qp->ibqp.event_handler(&ev,
 478                                         qp->ibqp.qp_context);
 479                         }
 480                 } else {
 481                         spin_unlock_irqrestore(&qp->state_lock, flags);
 482                 }
 483         }
 484
 485         do_complete(qp, wqe);
 486
 487         if (psn_compare(pkt->psn, qp->comp.psn) >= 0)
 488                 return COMPST_UPDATE_COMP;
 489         else
 490                 return COMPST_DONE;
 491 }
 492
 493 static inline enum comp_state complete_wqe(struct rxe_qp *qp,
 494                                            struct rxe_pkt_info *pkt,
 495                                            struct rxe_send_wqe *wqe)
 496 {
 497         qp->comp.opcode = -1;
 498
 499         if (pkt) {
 500                 if (psn_compare(pkt->psn, qp->comp.psn) >= 0)
 501                         qp->comp.psn = (pkt->psn + 1) & BTH_PSN_MASK;
 502
 503                 if (qp->req.wait_psn) {
 504                         qp->req.wait_psn = 0;
 505                         rxe_run_task(&qp->req.task, 1);
 506                 }
 507         }
 508
 509         do_complete(qp, wqe);
 510
 511         return COMPST_GET_WQE;
 512 }
 513
 514 static void rxe_drain_resp_pkts(struct rxe_qp *qp, bool notify)
 515 {
 516         struct sk_buff *skb;
 517         struct rxe_send_wqe *wqe;
 518
 519         while ((skb = skb_dequeue(&qp->resp_pkts))) {
 520                 rxe_drop_ref(qp);
 521                 kfree_skb(skb);
 522         }
 523
 524         while ((wqe = queue_head(qp->sq.queue))) {
 525                 if (notify) {
 526                         wqe->status = IB_WC_WR_FLUSH_ERR;
 527                         do_complete(qp, wqe);
 528                 } else {
 529                         advance_consumer(qp->sq.queue);
 530                 }
 531         }
 532 }
 533
 534 int rxe_completer(void *arg)
 535 {
 536         struct rxe_qp *qp = (struct rxe_qp *)arg;
 537         struct rxe_send_wqe *wqe = wqe;
 538         struct sk_buff *skb = NULL;
 539         struct rxe_pkt_info *pkt = NULL;
 540         enum comp_state state;
 541
 542         rxe_add_ref(qp);
 543
 544         if (!qp->valid || qp->req.state == QP_STATE_ERROR ||
 545             qp->req.state == QP_STATE_RESET) {
 546                 rxe_drain_resp_pkts(qp, qp->valid &&
 547                                     qp->req.state == QP_STATE_ERROR);
 548                 goto exit;
 549         }
 550
 551         if (qp->comp.timeout) {
 552                 qp->comp.timeout_retry = 1;
 553                 qp->comp.timeout = 0;
 554         } else {
 555                 qp->comp.timeout_retry = 0;
 556         }
 557
 558         if (qp->req.need_retry)
 559                 goto exit;
 560
 561         state = COMPST_GET_ACK;
 562
 563         while (1) {
 564                 pr_debug("qp#%d state = %s\n", qp_num(qp),
 565                          comp_state_name[state]);
 566                 switch (state) {
 567                 case COMPST_GET_ACK:
 568                         skb = skb_dequeue(&qp->resp_pkts);
 569                         if (skb) {
 570                                 pkt = SKB_TO_PKT(skb);
 571                                 qp->comp.timeout_retry = 0;
 572                         }
 573                         state = COMPST_GET_WQE;
 574                         break;
 575
 576                 case COMPST_GET_WQE:
 577                         state = get_wqe(qp, pkt, &wqe);
 578                         break;
 579
 580                 case COMPST_CHECK_PSN:
 581                         state = check_psn(qp, pkt, wqe);
 582                         break;
 583
 584                 case COMPST_CHECK_ACK:
 585                         state = check_ack(qp, pkt, wqe);
 586                         break;
 587
 588                 case COMPST_READ:
 589                         state = do_read(qp, pkt, wqe);
 590                         break;
 591
 592                 case COMPST_ATOMIC:
 593                         state = do_atomic(qp, pkt, wqe);
 594                         break;
 595
 596                 case COMPST_WRITE_SEND:
 597                         if (wqe->state == wqe_state_pending &&
 598                             wqe->last_psn == pkt->psn)
 599                                 state = COMPST_COMP_ACK;
 600                         else
 601                                 state = COMPST_UPDATE_COMP;
 602                         break;
 603
 604                 case COMPST_COMP_ACK:
 605                         state = complete_ack(qp, pkt, wqe);
 606                         break;
 607
 608                 case COMPST_COMP_WQE:
 609                         state = complete_wqe(qp, pkt, wqe);
 610                         break;
 611
 612                 case COMPST_UPDATE_COMP:
 613                         if (pkt->mask & RXE_END_MASK)
 614                                 qp->comp.opcode = -1;
 615                         else
 616                                 qp->comp.opcode = pkt->opcode;
 617
 618                         if (psn_compare(pkt->psn, qp->comp.psn) >= 0)
 619                                 qp->comp.psn = (pkt->psn + 1) & BTH_PSN_MASK;
 620
 621                         if (qp->req.wait_psn) {
 622                                 qp->req.wait_psn = 0;
 623                                 rxe_run_task(&qp->req.task, 1);
 624                         }
 625
 626                         state = COMPST_DONE;
 627                         break;
 628
 629                 case COMPST_DONE:
 630                         if (pkt) {
 631                                 rxe_drop_ref(pkt->qp);
 632                                 kfree_skb(skb);
 633                                 skb = NULL;
 634                         }
 635                         goto done;
 636
 637                 case COMPST_EXIT:
 638                         if (qp->comp.timeout_retry && wqe) {
 639                                 state = COMPST_ERROR_RETRY;
 640                                 break;
 641                         }
 642
 643                         /* re reset the timeout counter if
 644                          * (1) QP is type RC
 645                          * (2) the QP is alive
 646                          * (3) there is a packet sent by the requester that
 647                          *     might be acked (we still might get spurious
 648                          *     timeouts but try to keep them as few as possible)
 649                          * (4) the timeout parameter is set
 650                          */
 651                         if ((qp_type(qp) == IB_QPT_RC) &&
 652                             (qp->req.state == QP_STATE_READY) &&
 653                             (psn_compare(qp->req.psn, qp->comp.psn) > 0) &&
 654                             qp->qp_timeout_jiffies)
 655                                 mod_timer(&qp->retrans_timer,
 656                                           jiffies + qp->qp_timeout_jiffies);
 657                         WARN_ON_ONCE(skb);
 658                         goto exit;
 659
 660                 case COMPST_ERROR_RETRY:
 661                         /* we come here if the retry timer fired and we did
 662                          * not receive a response packet. try to retry the send
 663                          * queue if that makes sense and the limits have not
 664                          * been exceeded. remember that some timeouts are
 665                          * spurious since we do not reset the timer but kick
 666                          * it down the road or let it expire
 667                          */
 668
 669                         /* there is nothing to retry in this case */
 670                         if (!wqe || (wqe->state == wqe_state_posted)) {
 671                                 WARN_ON_ONCE(skb);
 672                                 goto exit;
 673                         }
 674
 675                         if (qp->comp.retry_cnt > 0) {
 676                                 if (qp->comp.retry_cnt != 7)
 677                                         qp->comp.retry_cnt--;
 678
 679                                 /* no point in retrying if we have already
 680                                  * seen the last ack that the requester could
 681                                  * have caused
 682                                  */
 683                                 if (psn_compare(qp->req.psn,
 684                                                 qp->comp.psn) > 0) {
 685                                         /* tell the requester to retry the
 686                                          * send send queue next time around
 687                                          */
 688                                         qp->req.need_retry = 1;
 689                                         rxe_run_task(&qp->req.task, 1);
 690                                 }
 691
 692                                 if (pkt) {
 693                                         rxe_drop_ref(pkt->qp);
 694                                         kfree_skb(skb);
 695                                         skb = NULL;
 696                                 }
 697
 698                                 WARN_ON_ONCE(skb);
 699                                 goto exit;
 700
 701                         } else {
 702                                 wqe->status = IB_WC_RETRY_EXC_ERR;
 703                                 state = COMPST_ERROR;
 704                         }
 705                         break;
 706
 707                 case COMPST_RNR_RETRY:
 708                         if (qp->comp.rnr_retry > 0) {
 709                                 if (qp->comp.rnr_retry != 7)
 710                                         qp->comp.rnr_retry--;
 711
 712                                 qp->req.need_retry = 1;
 713                                 pr_debug("qp#%d set rnr nak timer\n",
 714                                          qp_num(qp));
 715                                 mod_timer(&qp->rnr_nak_timer,
 716                                           jiffies + rnrnak_jiffies(aeth_syn(pkt)
 717                                                 & ~AETH_TYPE_MASK));
 718                                 rxe_drop_ref(pkt->qp);
 719                                 kfree_skb(skb);
 720                                 skb = NULL;
 721                                 goto exit;
 722                         } else {
 723                                 wqe->status = IB_WC_RNR_RETRY_EXC_ERR;
 724                                 state = COMPST_ERROR;
 725                         }
 726                         break;
 727
 728                 case COMPST_ERROR:
 729                         WARN_ON_ONCE(wqe->status == IB_WC_SUCCESS);
 730                         do_complete(qp, wqe);
 731                         rxe_qp_error(qp);
 732
 733                         if (pkt) {
 734                                 rxe_drop_ref(pkt->qp);
 735                                 kfree_skb(skb);
 736                                 skb = NULL;
 737                         }
 738
 739                         WARN_ON_ONCE(skb);
 740                         goto exit;
 741                 }
 742         }
 743
 744 exit:
 745         /* we come here if we are done with processing and want the task to
 746          * exit from the loop calling us
 747          */
 748         WARN_ON_ONCE(skb);
 749         rxe_drop_ref(qp);
 750         return -EAGAIN;
 751
 752 done:
 753         /* we come here if we have processed a packet we want the task to call
 754          * us again to see if there is anything else to do
 755          */
 756         WARN_ON_ONCE(skb);
 757         rxe_drop_ref(qp);
 758         return 0;
 759 }