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         if (must_sched != 0)
 158                 rxe_counter_inc(rxe, RXE_CNT_COMPLETER_SCHED);
 159         rxe_run_task(&qp->comp.task, must_sched);
 160 }
 161
 162 static inline enum comp_state get_wqe(struct rxe_qp *qp,
 163                                       struct rxe_pkt_info *pkt,
 164                                       struct rxe_send_wqe **wqe_p)
 165 {
 166         struct rxe_send_wqe *wqe;
 167
 168         /* we come here whether or not we found a response packet to see if
 169          * there are any posted WQEs
 170          */
 171         wqe = queue_head(qp->sq.queue);
 172         *wqe_p = wqe;
 173
 174         /* no WQE or requester has not started it yet */
 175         if (!wqe || wqe->state == wqe_state_posted)
 176                 return pkt ? COMPST_DONE : COMPST_EXIT;
 177
 178         /* WQE does not require an ack */
 179         if (wqe->state == wqe_state_done)
 180                 return COMPST_COMP_WQE;
 181
 182         /* WQE caused an error */
 183         if (wqe->state == wqe_state_error)
 184                 return COMPST_ERROR;
 185
 186         /* we have a WQE, if we also have an ack check its PSN */
 187         return pkt ? COMPST_CHECK_PSN : COMPST_EXIT;
 188 }
 189
 190 static inline void reset_retry_counters(struct rxe_qp *qp)
 191 {
 192         qp->comp.retry_cnt = qp->attr.retry_cnt;
 193         qp->comp.rnr_retry = qp->attr.rnr_retry;
 194 }
 195
 196 static inline enum comp_state check_psn(struct rxe_qp *qp,
 197                                         struct rxe_pkt_info *pkt,
 198                                         struct rxe_send_wqe *wqe)
 199 {
 200         s32 diff;
 201
 202         /* check to see if response is past the oldest WQE. if it is, complete
 203          * send/write or error read/atomic
 204          */
 205         diff = psn_compare(pkt->psn, wqe->last_psn);
 206         if (diff > 0) {
 207                 if (wqe->state == wqe_state_pending) {
 208                         if (wqe->mask & WR_ATOMIC_OR_READ_MASK)
 209                                 return COMPST_ERROR_RETRY;
 210
 211                         reset_retry_counters(qp);
 212                         return COMPST_COMP_WQE;
 213                 } else {
 214                         return COMPST_DONE;
 215                 }
 216         }
 217
 218         /* compare response packet to expected response */
 219         diff = psn_compare(pkt->psn, qp->comp.psn);
 220         if (diff < 0) {
 221                 /* response is most likely a retried packet if it matches an
 222                  * uncompleted WQE go complete it else ignore it
 223                  */
 224                 if (pkt->psn == wqe->last_psn)
 225                         return COMPST_COMP_ACK;
 226                 else
 227                         return COMPST_DONE;
 228         } else if ((diff > 0) && (wqe->mask & WR_ATOMIC_OR_READ_MASK)) {
 229                 return COMPST_DONE;
 230         } else {
 231                 return COMPST_CHECK_ACK;
 232         }
 233 }
 234
 235 static inline enum comp_state check_ack(struct rxe_qp *qp,
 236                                         struct rxe_pkt_info *pkt,
 237                                         struct rxe_send_wqe *wqe)
 238 {
 239         unsigned int mask = pkt->mask;
 240         u8 syn;
 241         struct rxe_dev *rxe = to_rdev(qp->ibqp.device);
 242
 243         /* Check the sequence only */
 244         switch (qp->comp.opcode) {
 245         case -1:
 246                 /* Will catch all *_ONLY cases. */
 247                 if (!(mask & RXE_START_MASK))
 248                         return COMPST_ERROR;
 249
 250                 break;
 251
 252         case IB_OPCODE_RC_RDMA_READ_RESPONSE_FIRST:
 253         case IB_OPCODE_RC_RDMA_READ_RESPONSE_MIDDLE:
 254                 if (pkt->opcode != IB_OPCODE_RC_RDMA_READ_RESPONSE_MIDDLE &&
 255                     pkt->opcode != IB_OPCODE_RC_RDMA_READ_RESPONSE_LAST) {
 256                         /* read retries of partial data may restart from
 257                          * read response first or response only.
 258                          */
 259                         if ((pkt->psn == wqe->first_psn &&
 260                              pkt->opcode ==
 261                              IB_OPCODE_RC_RDMA_READ_RESPONSE_FIRST) ||
 262                             (wqe->first_psn == wqe->last_psn &&
 263                              pkt->opcode ==
 264                              IB_OPCODE_RC_RDMA_READ_RESPONSE_ONLY))
 265                                 break;
 266
 267                         return COMPST_ERROR;
 268                 }
 269                 break;
 270         default:
 271                 WARN_ON_ONCE(1);
 272         }
 273
 274         /* Check operation validity. */
 275         switch (pkt->opcode) {
 276         case IB_OPCODE_RC_RDMA_READ_RESPONSE_FIRST:
 277         case IB_OPCODE_RC_RDMA_READ_RESPONSE_LAST:
 278         case IB_OPCODE_RC_RDMA_READ_RESPONSE_ONLY:
 279                 syn = aeth_syn(pkt);
 280
 281                 if ((syn & AETH_TYPE_MASK) != AETH_ACK)
 282                         return COMPST_ERROR;
 283
 284                 /* Fall through (IB_OPCODE_RC_RDMA_READ_RESPONSE_MIDDLE
 285                  * doesn't have an AETH)
 286                  */
 287         case IB_OPCODE_RC_RDMA_READ_RESPONSE_MIDDLE:
 288                 if (wqe->wr.opcode != IB_WR_RDMA_READ &&
 289                     wqe->wr.opcode != IB_WR_RDMA_READ_WITH_INV) {
 290                         wqe->status = IB_WC_FATAL_ERR;
 291                         return COMPST_ERROR;
 292                 }
 293                 reset_retry_counters(qp);
 294                 return COMPST_READ;
 295
 296         case IB_OPCODE_RC_ATOMIC_ACKNOWLEDGE:
 297                 syn = aeth_syn(pkt);
 298
 299                 if ((syn & AETH_TYPE_MASK) != AETH_ACK)
 300                         return COMPST_ERROR;
 301
 302                 if (wqe->wr.opcode != IB_WR_ATOMIC_CMP_AND_SWP &&
 303                     wqe->wr.opcode != IB_WR_ATOMIC_FETCH_AND_ADD)
 304                         return COMPST_ERROR;
 305                 reset_retry_counters(qp);
 306                 return COMPST_ATOMIC;
 307
 308         case IB_OPCODE_RC_ACKNOWLEDGE:
 309                 syn = aeth_syn(pkt);
 310                 switch (syn & AETH_TYPE_MASK) {
 311                 case AETH_ACK:
 312                         reset_retry_counters(qp);
 313                         return COMPST_WRITE_SEND;
 314
 315                 case AETH_RNR_NAK:
 316                         rxe_counter_inc(rxe, RXE_CNT_RCV_RNR);
 317                         return COMPST_RNR_RETRY;
 318
 319                 case AETH_NAK:
 320                         switch (syn) {
 321                         case AETH_NAK_PSN_SEQ_ERROR:
 322                                 /* a nak implicitly acks all packets with psns
 323                                  * before
 324                                  */
 325                                 if (psn_compare(pkt->psn, qp->comp.psn) > 0) {
 326                                         rxe_counter_inc(rxe,
 327                                                         RXE_CNT_RCV_SEQ_ERR);
 328                                         qp->comp.psn = pkt->psn;
 329                                         if (qp->req.wait_psn) {
 330                                                 qp->req.wait_psn = 0;
 331                                                 rxe_run_task(&qp->req.task, 1);
 332                                         }
 333                                 }
 334                                 return COMPST_ERROR_RETRY;
 335
 336                         case AETH_NAK_INVALID_REQ:
 337                                 wqe->status = IB_WC_REM_INV_REQ_ERR;
 338                                 return COMPST_ERROR;
 339
 340                         case AETH_NAK_REM_ACC_ERR:
 341                                 wqe->status = IB_WC_REM_ACCESS_ERR;
 342                                 return COMPST_ERROR;
 343
 344                         case AETH_NAK_REM_OP_ERR:
 345                                 wqe->status = IB_WC_REM_OP_ERR;
 346                                 return COMPST_ERROR;
 347
 348                         default:
 349                                 pr_warn("unexpected nak %x\n", syn);
 350                                 wqe->status = IB_WC_REM_OP_ERR;
 351                                 return COMPST_ERROR;
 352                         }
 353
 354                 default:
 355                         return COMPST_ERROR;
 356                 }
 357                 break;
 358
 359         default:
 360                 pr_warn("unexpected opcode\n");
 361         }
 362
 363         return COMPST_ERROR;
 364 }
 365
 366 static inline enum comp_state do_read(struct rxe_qp *qp,
 367                                       struct rxe_pkt_info *pkt,
 368                                       struct rxe_send_wqe *wqe)
 369 {
 370         struct rxe_dev *rxe = to_rdev(qp->ibqp.device);
 371         int ret;
 372
 373         ret = copy_data(rxe, qp->pd, IB_ACCESS_LOCAL_WRITE,
 374                         &wqe->dma, payload_addr(pkt),
 375                         payload_size(pkt), to_mem_obj, NULL);
 376         if (ret)
 377                 return COMPST_ERROR;
 378
 379         if (wqe->dma.resid == 0 && (pkt->mask & RXE_END_MASK))
 380                 return COMPST_COMP_ACK;
 381         else
 382                 return COMPST_UPDATE_COMP;
 383 }
 384
 385 static inline enum comp_state do_atomic(struct rxe_qp *qp,
 386                                         struct rxe_pkt_info *pkt,
 387                                         struct rxe_send_wqe *wqe)
 388 {
 389         struct rxe_dev *rxe = to_rdev(qp->ibqp.device);
 390         int ret;
 391
 392         u64 atomic_orig = atmack_orig(pkt);
 393
 394         ret = copy_data(rxe, qp->pd, IB_ACCESS_LOCAL_WRITE,
 395                         &wqe->dma, &atomic_orig,
 396                         sizeof(u64), to_mem_obj, NULL);
 397         if (ret)
 398                 return COMPST_ERROR;
 399         else
 400                 return COMPST_COMP_ACK;
 401 }
 402
 403 static void make_send_cqe(struct rxe_qp *qp, struct rxe_send_wqe *wqe,
 404                           struct rxe_cqe *cqe)
 405 {
 406         memset(cqe, 0, sizeof(*cqe));
 407
 408         if (!qp->is_user) {
 409                 struct ib_wc            *wc     = &cqe->ibwc;
 410
 411                 wc->wr_id               = wqe->wr.wr_id;
 412                 wc->status              = wqe->status;
 413                 wc->opcode              = wr_to_wc_opcode(wqe->wr.opcode);
 414                 if (wqe->wr.opcode == IB_WR_RDMA_WRITE_WITH_IMM ||
 415                     wqe->wr.opcode == IB_WR_SEND_WITH_IMM)
 416                         wc->wc_flags = IB_WC_WITH_IMM;
 417                 wc->byte_len            = wqe->dma.length;
 418                 wc->qp                  = &qp->ibqp;
 419         } else {
 420                 struct ib_uverbs_wc     *uwc    = &cqe->uibwc;
 421
 422                 uwc->wr_id              = wqe->wr.wr_id;
 423                 uwc->status             = wqe->status;
 424                 uwc->opcode             = wr_to_wc_opcode(wqe->wr.opcode);
 425                 if (wqe->wr.opcode == IB_WR_RDMA_WRITE_WITH_IMM ||
 426                     wqe->wr.opcode == IB_WR_SEND_WITH_IMM)
 427                         uwc->wc_flags = IB_WC_WITH_IMM;
 428                 uwc->byte_len           = wqe->dma.length;
 429                 uwc->qp_num             = qp->ibqp.qp_num;
 430         }
 431 }
 432
 433 /*
 434  * IBA Spec. Section 10.7.3.1 SIGNALED COMPLETIONS
 435  * ---------8<---------8<-------------
 436  * ...Note that if a completion error occurs, a Work Completion
 437  * will always be generated, even if the signaling
 438  * indicator requests an Unsignaled Completion.
 439  * ---------8<---------8<-------------
 440  */
 441 static void do_complete(struct rxe_qp *qp, struct rxe_send_wqe *wqe)
 442 {
 443         struct rxe_cqe cqe;
 444
 445         if ((qp->sq_sig_type == IB_SIGNAL_ALL_WR) ||
 446             (wqe->wr.send_flags & IB_SEND_SIGNALED) ||
 447             wqe->status != IB_WC_SUCCESS) {
 448                 make_send_cqe(qp, wqe, &cqe);
 449                 advance_consumer(qp->sq.queue);
 450                 rxe_cq_post(qp->scq, &cqe, 0);
 451         } else {
 452                 advance_consumer(qp->sq.queue);
 453         }
 454
 455         /*
 456          * we completed something so let req run again
 457          * if it is trying to fence
 458          */
 459         if (qp->req.wait_fence) {
 460                 qp->req.wait_fence = 0;
 461                 rxe_run_task(&qp->req.task, 1);
 462         }
 463 }
 464
 465 static inline enum comp_state complete_ack(struct rxe_qp *qp,
 466                                            struct rxe_pkt_info *pkt,
 467                                            struct rxe_send_wqe *wqe)
 468 {
 469         unsigned long flags;
 470
 471         if (wqe->has_rd_atomic) {
 472                 wqe->has_rd_atomic = 0;
 473                 atomic_inc(&qp->req.rd_atomic);
 474                 if (qp->req.need_rd_atomic) {
 475                         qp->comp.timeout_retry = 0;
 476                         qp->req.need_rd_atomic = 0;
 477                         rxe_run_task(&qp->req.task, 1);
 478                 }
 479         }
 480
 481         if (unlikely(qp->req.state == QP_STATE_DRAIN)) {
 482                 /* state_lock used by requester & completer */
 483                 spin_lock_irqsave(&qp->state_lock, flags);
 484                 if ((qp->req.state == QP_STATE_DRAIN) &&
 485                     (qp->comp.psn == qp->req.psn)) {
 486                         qp->req.state = QP_STATE_DRAINED;
 487                         spin_unlock_irqrestore(&qp->state_lock, flags);
 488
 489                         if (qp->ibqp.event_handler) {
 490                                 struct ib_event ev;
 491
 492                                 ev.device = qp->ibqp.device;
 493                                 ev.element.qp = &qp->ibqp;
 494                                 ev.event = IB_EVENT_SQ_DRAINED;
 495                                 qp->ibqp.event_handler(&ev,
 496                                         qp->ibqp.qp_context);
 497                         }
 498                 } else {
 499                         spin_unlock_irqrestore(&qp->state_lock, flags);
 500                 }
 501         }
 502
 503         do_complete(qp, wqe);
 504
 505         if (psn_compare(pkt->psn, qp->comp.psn) >= 0)
 506                 return COMPST_UPDATE_COMP;
 507         else
 508                 return COMPST_DONE;
 509 }
 510
 511 static inline enum comp_state complete_wqe(struct rxe_qp *qp,
 512                                            struct rxe_pkt_info *pkt,
 513                                            struct rxe_send_wqe *wqe)
 514 {
 515         if (pkt && wqe->state == wqe_state_pending) {
 516                 if (psn_compare(wqe->last_psn, qp->comp.psn) >= 0) {
 517                         qp->comp.psn = (wqe->last_psn + 1) & BTH_PSN_MASK;
 518                         qp->comp.opcode = -1;
 519                 }
 520
 521                 if (qp->req.wait_psn) {
 522                         qp->req.wait_psn = 0;
 523                         rxe_run_task(&qp->req.task, 1);
 524                 }
 525         }
 526
 527         do_complete(qp, wqe);
 528
 529         return COMPST_GET_WQE;
 530 }
 531
 532 static void rxe_drain_resp_pkts(struct rxe_qp *qp, bool notify)
 533 {
 534         struct sk_buff *skb;
 535         struct rxe_send_wqe *wqe;
 536
 537         while ((skb = skb_dequeue(&qp->resp_pkts))) {
 538                 rxe_drop_ref(qp);
 539                 kfree_skb(skb);
 540         }
 541
 542         while ((wqe = queue_head(qp->sq.queue))) {
 543                 if (notify) {
 544                         wqe->status = IB_WC_WR_FLUSH_ERR;
 545                         do_complete(qp, wqe);
 546                 } else {
 547                         advance_consumer(qp->sq.queue);
 548                 }
 549         }
 550 }
 551
 552 int rxe_completer(void *arg)
 553 {
 554         struct rxe_qp *qp = (struct rxe_qp *)arg;
 555         struct rxe_dev *rxe = to_rdev(qp->ibqp.device);
 556         struct rxe_send_wqe *wqe = wqe;
 557         struct sk_buff *skb = NULL;
 558         struct rxe_pkt_info *pkt = NULL;
 559         enum comp_state state;
 560
 561         rxe_add_ref(qp);
 562
 563         if (!qp->valid || qp->req.state == QP_STATE_ERROR ||
 564             qp->req.state == QP_STATE_RESET) {
 565                 rxe_drain_resp_pkts(qp, qp->valid &&
 566                                     qp->req.state == QP_STATE_ERROR);
 567                 goto exit;
 568         }
 569
 570         if (qp->comp.timeout) {
 571                 qp->comp.timeout_retry = 1;
 572                 qp->comp.timeout = 0;
 573         } else {
 574                 qp->comp.timeout_retry = 0;
 575         }
 576
 577         if (qp->req.need_retry)
 578                 goto exit;
 579
 580         state = COMPST_GET_ACK;
 581
 582         while (1) {
 583                 pr_debug("qp#%d state = %s\n", qp_num(qp),
 584                          comp_state_name[state]);
 585                 switch (state) {
 586                 case COMPST_GET_ACK:
 587                         skb = skb_dequeue(&qp->resp_pkts);
 588                         if (skb) {
 589                                 pkt = SKB_TO_PKT(skb);
 590                                 qp->comp.timeout_retry = 0;
 591                         }
 592                         state = COMPST_GET_WQE;
 593                         break;
 594
 595                 case COMPST_GET_WQE:
 596                         state = get_wqe(qp, pkt, &wqe);
 597                         break;
 598
 599                 case COMPST_CHECK_PSN:
 600                         state = check_psn(qp, pkt, wqe);
 601                         break;
 602
 603                 case COMPST_CHECK_ACK:
 604                         state = check_ack(qp, pkt, wqe);
 605                         break;
 606
 607                 case COMPST_READ:
 608                         state = do_read(qp, pkt, wqe);
 609                         break;
 610
 611                 case COMPST_ATOMIC:
 612                         state = do_atomic(qp, pkt, wqe);
 613                         break;
 614
 615                 case COMPST_WRITE_SEND:
 616                         if (wqe->state == wqe_state_pending &&
 617                             wqe->last_psn == pkt->psn)
 618                                 state = COMPST_COMP_ACK;
 619                         else
 620                                 state = COMPST_UPDATE_COMP;
 621                         break;
 622
 623                 case COMPST_COMP_ACK:
 624                         state = complete_ack(qp, pkt, wqe);
 625                         break;
 626
 627                 case COMPST_COMP_WQE:
 628                         state = complete_wqe(qp, pkt, wqe);
 629                         break;
 630
 631                 case COMPST_UPDATE_COMP:
 632                         if (pkt->mask & RXE_END_MASK)
 633                                 qp->comp.opcode = -1;
 634                         else
 635                                 qp->comp.opcode = pkt->opcode;
 636
 637                         if (psn_compare(pkt->psn, qp->comp.psn) >= 0)
 638                                 qp->comp.psn = (pkt->psn + 1) & BTH_PSN_MASK;
 639
 640                         if (qp->req.wait_psn) {
 641                                 qp->req.wait_psn = 0;
 642                                 rxe_run_task(&qp->req.task, 1);
 643                         }
 644
 645                         state = COMPST_DONE;
 646                         break;
 647
 648                 case COMPST_DONE:
 649                         if (pkt) {
 650                                 rxe_drop_ref(pkt->qp);
 651                                 kfree_skb(skb);
 652                                 skb = NULL;
 653                         }
 654                         goto done;
 655
 656                 case COMPST_EXIT:
 657                         if (qp->comp.timeout_retry && wqe) {
 658                                 state = COMPST_ERROR_RETRY;
 659                                 break;
 660                         }
 661
 662                         /* re reset the timeout counter if
 663                          * (1) QP is type RC
 664                          * (2) the QP is alive
 665                          * (3) there is a packet sent by the requester that
 666                          *     might be acked (we still might get spurious
 667                          *     timeouts but try to keep them as few as possible)
 668                          * (4) the timeout parameter is set
 669                          */
 670                         if ((qp_type(qp) == IB_QPT_RC) &&
 671                             (qp->req.state == QP_STATE_READY) &&
 672                             (psn_compare(qp->req.psn, qp->comp.psn) > 0) &&
 673                             qp->qp_timeout_jiffies)
 674                                 mod_timer(&qp->retrans_timer,
 675                                           jiffies + qp->qp_timeout_jiffies);
 676                         WARN_ON_ONCE(skb);
 677                         goto exit;
 678
 679                 case COMPST_ERROR_RETRY:
 680                         /* we come here if the retry timer fired and we did
 681                          * not receive a response packet. try to retry the send
 682                          * queue if that makes sense and the limits have not
 683                          * been exceeded. remember that some timeouts are
 684                          * spurious since we do not reset the timer but kick
 685                          * it down the road or let it expire
 686                          */
 687
 688                         /* there is nothing to retry in this case */
 689                         if (!wqe || (wqe->state == wqe_state_posted)) {
 690                                 WARN_ON_ONCE(skb);
 691                                 goto exit;
 692                         }
 693
 694                         if (qp->comp.retry_cnt > 0) {
 695                                 if (qp->comp.retry_cnt != 7)
 696                                         qp->comp.retry_cnt--;
 697
 698                                 /* no point in retrying if we have already
 699                                  * seen the last ack that the requester could
 700                                  * have caused
 701                                  */
 702                                 if (psn_compare(qp->req.psn,
 703                                                 qp->comp.psn) > 0) {
 704                                         /* tell the requester to retry the
 705                                          * send queue next time around
 706                                          */
 707                                         rxe_counter_inc(rxe,
 708                                                         RXE_CNT_COMP_RETRY);
 709                                         qp->req.need_retry = 1;
 710                                         rxe_run_task(&qp->req.task, 1);
 711                                 }
 712
 713                                 if (pkt) {
 714                                         rxe_drop_ref(pkt->qp);
 715                                         kfree_skb(skb);
 716                                         skb = NULL;
 717                                 }
 718
 719                                 WARN_ON_ONCE(skb);
 720                                 goto exit;
 721
 722                         } else {
 723                                 rxe_counter_inc(rxe, RXE_CNT_RETRY_EXCEEDED);
 724                                 wqe->status = IB_WC_RETRY_EXC_ERR;
 725                                 state = COMPST_ERROR;
 726                         }
 727                         break;
 728
 729                 case COMPST_RNR_RETRY:
 730                         if (qp->comp.rnr_retry > 0) {
 731                                 if (qp->comp.rnr_retry != 7)
 732                                         qp->comp.rnr_retry--;
 733
 734                                 qp->req.need_retry = 1;
 735                                 pr_debug("qp#%d set rnr nak timer\n",
 736                                          qp_num(qp));
 737                                 mod_timer(&qp->rnr_nak_timer,
 738                                           jiffies + rnrnak_jiffies(aeth_syn(pkt)
 739                                                 & ~AETH_TYPE_MASK));
 740                                 rxe_drop_ref(pkt->qp);
 741                                 kfree_skb(skb);
 742                                 skb = NULL;
 743                                 goto exit;
 744                         } else {
 745                                 rxe_counter_inc(rxe,
 746                                                 RXE_CNT_RNR_RETRY_EXCEEDED);
 747                                 wqe->status = IB_WC_RNR_RETRY_EXC_ERR;
 748                                 state = COMPST_ERROR;
 749                         }
 750                         break;
 751
 752                 case COMPST_ERROR:
 753                         WARN_ON_ONCE(wqe->status == IB_WC_SUCCESS);
 754                         do_complete(qp, wqe);
 755                         rxe_qp_error(qp);
 756
 757                         if (pkt) {
 758                                 rxe_drop_ref(pkt->qp);
 759                                 kfree_skb(skb);
 760                                 skb = NULL;
 761                         }
 762
 763                         WARN_ON_ONCE(skb);
 764                         goto exit;
 765                 }
 766         }
 767
 768 exit:
 769         /* we come here if we are done with processing and want the task to
 770          * exit from the loop calling us
 771          */
 772         WARN_ON_ONCE(skb);
 773         rxe_drop_ref(qp);
 774         return -EAGAIN;
 775
 776 done:
 777         /* we come here if we have processed a packet we want the task to call
 778          * us again to see if there is anything else to do
 779          */
 780         WARN_ON_ONCE(skb);
 781         rxe_drop_ref(qp);
 782         return 0;
 783 }