migration/colo.c

   1 /*
   2  * COarse-grain LOck-stepping Virtual Machines for Non-stop Service (COLO)
   3  * (a.k.a. Fault Tolerance or Continuous Replication)
   4  *
   5  * Copyright (c) 2016 HUAWEI TECHNOLOGIES CO., LTD.
   6  * Copyright (c) 2016 FUJITSU LIMITED
   7  * Copyright (c) 2016 Intel Corporation
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or
  10  * later.  See the COPYING file in the top-level directory.
  11  */
  12
  13 #include "qemu/osdep.h"
  14 #include "sysemu/sysemu.h"
  15 #include "qapi/error.h"
  16 #include "qapi/qapi-commands-migration.h"
  17 #include "qemu-file-channel.h"
  18 #include "migration.h"
  19 #include "qemu-file.h"
  20 #include "savevm.h"
  21 #include "migration/colo.h"
  22 #include "block.h"
  23 #include "io/channel-buffer.h"
  24 #include "trace.h"
  25 #include "qemu/error-report.h"
  26 #include "migration/failover.h"
  27 #include "replication.h"
  28 #include "net/colo-compare.h"
  29 #include "net/colo.h"
  30
  31 static bool vmstate_loading;
  32 static Notifier packets_compare_notifier;
  33
  34 #define COLO_BUFFER_BASE_SIZE (4 * 1024 * 1024)
  35
  36 bool migration_in_colo_state(void)
  37 {
  38     MigrationState *s = migrate_get_current();
  39
  40     return (s->state == MIGRATION_STATUS_COLO);
  41 }
  42
  43 bool migration_incoming_in_colo_state(void)
  44 {
  45     MigrationIncomingState *mis = migration_incoming_get_current();
  46
  47     return mis && (mis->state == MIGRATION_STATUS_COLO);
  48 }
  49
  50 static bool colo_runstate_is_stopped(void)
  51 {
  52     return runstate_check(RUN_STATE_COLO) || !runstate_is_running();
  53 }
  54
  55 static void secondary_vm_do_failover(void)
  56 {
  57     int old_state;
  58     MigrationIncomingState *mis = migration_incoming_get_current();
  59
  60     /* Can not do failover during the process of VM's loading VMstate, Or
  61      * it will break the secondary VM.
  62      */
  63     if (vmstate_loading) {
  64         old_state = failover_set_state(FAILOVER_STATUS_ACTIVE,
  65                         FAILOVER_STATUS_RELAUNCH);
  66         if (old_state != FAILOVER_STATUS_ACTIVE) {
  67             error_report("Unknown error while do failover for secondary VM,"
  68                          "old_state: %s", FailoverStatus_str(old_state));
  69         }
  70         return;
  71     }
  72
  73     migrate_set_state(&mis->state, MIGRATION_STATUS_COLO,
  74                       MIGRATION_STATUS_COMPLETED);
  75
  76     if (!autostart) {
  77         error_report("\"-S\" qemu option will be ignored in secondary side");
  78         /* recover runstate to normal migration finish state */
  79         autostart = true;
  80     }
  81     /*
  82      * Make sure COLO incoming thread not block in recv or send,
  83      * If mis->from_src_file and mis->to_src_file use the same fd,
  84      * The second shutdown() will return -1, we ignore this value,
  85      * It is harmless.
  86      */
  87     if (mis->from_src_file) {
  88         qemu_file_shutdown(mis->from_src_file);
  89     }
  90     if (mis->to_src_file) {
  91         qemu_file_shutdown(mis->to_src_file);
  92     }
  93
  94     old_state = failover_set_state(FAILOVER_STATUS_ACTIVE,
  95                                    FAILOVER_STATUS_COMPLETED);
  96     if (old_state != FAILOVER_STATUS_ACTIVE) {
  97         error_report("Incorrect state (%s) while doing failover for "
  98                      "secondary VM", FailoverStatus_str(old_state));
  99         return;
 100     }
 101     /* Notify COLO incoming thread that failover work is finished */
 102     qemu_sem_post(&mis->colo_incoming_sem);
 103     /* For Secondary VM, jump to incoming co */
 104     if (mis->migration_incoming_co) {
 105         qemu_coroutine_enter(mis->migration_incoming_co);
 106     }
 107 }
 108
 109 static void primary_vm_do_failover(void)
 110 {
 111     MigrationState *s = migrate_get_current();
 112     int old_state;
 113
 114     migrate_set_state(&s->state, MIGRATION_STATUS_COLO,
 115                       MIGRATION_STATUS_COMPLETED);
 116
 117     /*
 118      * Wake up COLO thread which may blocked in recv() or send(),
 119      * The s->rp_state.from_dst_file and s->to_dst_file may use the
 120      * same fd, but we still shutdown the fd for twice, it is harmless.
 121      */
 122     if (s->to_dst_file) {
 123         qemu_file_shutdown(s->to_dst_file);
 124     }
 125     if (s->rp_state.from_dst_file) {
 126         qemu_file_shutdown(s->rp_state.from_dst_file);
 127     }
 128
 129     old_state = failover_set_state(FAILOVER_STATUS_ACTIVE,
 130                                    FAILOVER_STATUS_COMPLETED);
 131     if (old_state != FAILOVER_STATUS_ACTIVE) {
 132         error_report("Incorrect state (%s) while doing failover for Primary VM",
 133                      FailoverStatus_str(old_state));
 134         return;
 135     }
 136     /* Notify COLO thread that failover work is finished */
 137     qemu_sem_post(&s->colo_exit_sem);
 138 }
 139
 140 void colo_do_failover(MigrationState *s)
 141 {
 142     /* Make sure VM stopped while failover happened. */
 143     if (!colo_runstate_is_stopped()) {
 144         vm_stop_force_state(RUN_STATE_COLO);
 145     }
 146
 147     if (get_colo_mode() == COLO_MODE_PRIMARY) {
 148         primary_vm_do_failover();
 149     } else {
 150         secondary_vm_do_failover();
 151     }
 152 }
 153
 154 void qmp_xen_set_replication(bool enable, bool primary,
 155                              bool has_failover, bool failover,
 156                              Error **errp)
 157 {
 158 #ifdef CONFIG_REPLICATION
 159     ReplicationMode mode = primary ?
 160                            REPLICATION_MODE_PRIMARY :
 161                            REPLICATION_MODE_SECONDARY;
 162
 163     if (has_failover && enable) {
 164         error_setg(errp, "Parameter 'failover' is only for"
 165                    " stopping replication");
 166         return;
 167     }
 168
 169     if (enable) {
 170         replication_start_all(mode, errp);
 171     } else {
 172         if (!has_failover) {
 173             failover = NULL;
 174         }
 175         replication_stop_all(failover, failover ? NULL : errp);
 176     }
 177 #else
 178     abort();
 179 #endif
 180 }
 181
 182 ReplicationStatus *qmp_query_xen_replication_status(Error **errp)
 183 {
 184 #ifdef CONFIG_REPLICATION
 185     Error *err = NULL;
 186     ReplicationStatus *s = g_new0(ReplicationStatus, 1);
 187
 188     replication_get_error_all(&err);
 189     if (err) {
 190         s->error = true;
 191         s->has_desc = true;
 192         s->desc = g_strdup(error_get_pretty(err));
 193     } else {
 194         s->error = false;
 195     }
 196
 197     error_free(err);
 198     return s;
 199 #else
 200     abort();
 201 #endif
 202 }
 203
 204 void qmp_xen_colo_do_checkpoint(Error **errp)
 205 {
 206 #ifdef CONFIG_REPLICATION
 207     replication_do_checkpoint_all(errp);
 208 #else
 209     abort();
 210 #endif
 211 }
 212
 213 static void colo_send_message(QEMUFile *f, COLOMessage msg,
 214                               Error **errp)
 215 {
 216     int ret;
 217
 218     if (msg >= COLO_MESSAGE__MAX) {
 219         error_setg(errp, "%s: Invalid message", __func__);
 220         return;
 221     }
 222     qemu_put_be32(f, msg);
 223     qemu_fflush(f);
 224
 225     ret = qemu_file_get_error(f);
 226     if (ret < 0) {
 227         error_setg_errno(errp, -ret, "Can't send COLO message");
 228     }
 229     trace_colo_send_message(COLOMessage_str(msg));
 230 }
 231
 232 static void colo_send_message_value(QEMUFile *f, COLOMessage msg,
 233                                     uint64_t value, Error **errp)
 234 {
 235     Error *local_err = NULL;
 236     int ret;
 237
 238     colo_send_message(f, msg, &local_err);
 239     if (local_err) {
 240         error_propagate(errp, local_err);
 241         return;
 242     }
 243     qemu_put_be64(f, value);
 244     qemu_fflush(f);
 245
 246     ret = qemu_file_get_error(f);
 247     if (ret < 0) {
 248         error_setg_errno(errp, -ret, "Failed to send value for message:%s",
 249                          COLOMessage_str(msg));
 250     }
 251 }
 252
 253 static COLOMessage colo_receive_message(QEMUFile *f, Error **errp)
 254 {
 255     COLOMessage msg;
 256     int ret;
 257
 258     msg = qemu_get_be32(f);
 259     ret = qemu_file_get_error(f);
 260     if (ret < 0) {
 261         error_setg_errno(errp, -ret, "Can't receive COLO message");
 262         return msg;
 263     }
 264     if (msg >= COLO_MESSAGE__MAX) {
 265         error_setg(errp, "%s: Invalid message", __func__);
 266         return msg;
 267     }
 268     trace_colo_receive_message(COLOMessage_str(msg));
 269     return msg;
 270 }
 271
 272 static void colo_receive_check_message(QEMUFile *f, COLOMessage expect_msg,
 273                                        Error **errp)
 274 {
 275     COLOMessage msg;
 276     Error *local_err = NULL;
 277
 278     msg = colo_receive_message(f, &local_err);
 279     if (local_err) {
 280         error_propagate(errp, local_err);
 281         return;
 282     }
 283     if (msg != expect_msg) {
 284         error_setg(errp, "Unexpected COLO message %d, expected %d",
 285                           msg, expect_msg);
 286     }
 287 }
 288
 289 static uint64_t colo_receive_message_value(QEMUFile *f, uint32_t expect_msg,
 290                                            Error **errp)
 291 {
 292     Error *local_err = NULL;
 293     uint64_t value;
 294     int ret;
 295
 296     colo_receive_check_message(f, expect_msg, &local_err);
 297     if (local_err) {
 298         error_propagate(errp, local_err);
 299         return 0;
 300     }
 301
 302     value = qemu_get_be64(f);
 303     ret = qemu_file_get_error(f);
 304     if (ret < 0) {
 305         error_setg_errno(errp, -ret, "Failed to get value for COLO message: %s",
 306                          COLOMessage_str(expect_msg));
 307     }
 308     return value;
 309 }
 310
 311 static int colo_do_checkpoint_transaction(MigrationState *s,
 312                                           QIOChannelBuffer *bioc,
 313                                           QEMUFile *fb)
 314 {
 315     Error *local_err = NULL;
 316     int ret = -1;
 317
 318     colo_send_message(s->to_dst_file, COLO_MESSAGE_CHECKPOINT_REQUEST,
 319                       &local_err);
 320     if (local_err) {
 321         goto out;
 322     }
 323
 324     colo_receive_check_message(s->rp_state.from_dst_file,
 325                     COLO_MESSAGE_CHECKPOINT_REPLY, &local_err);
 326     if (local_err) {
 327         goto out;
 328     }
 329     /* Reset channel-buffer directly */
 330     qio_channel_io_seek(QIO_CHANNEL(bioc), 0, 0, NULL);
 331     bioc->usage = 0;
 332
 333     qemu_mutex_lock_iothread();
 334     if (failover_get_state() != FAILOVER_STATUS_NONE) {
 335         qemu_mutex_unlock_iothread();
 336         goto out;
 337     }
 338     vm_stop_force_state(RUN_STATE_COLO);
 339     qemu_mutex_unlock_iothread();
 340     trace_colo_vm_state_change("run", "stop");
 341     /*
 342      * Failover request bh could be called after vm_stop_force_state(),
 343      * So we need check failover_request_is_active() again.
 344      */
 345     if (failover_get_state() != FAILOVER_STATUS_NONE) {
 346         goto out;
 347     }
 348
 349     colo_notify_compares_event(NULL, COLO_EVENT_CHECKPOINT, &local_err);
 350     if (local_err) {
 351         goto out;
 352     }
 353
 354     /* Disable block migration */
 355     migrate_set_block_enabled(false, &local_err);
 356     qemu_savevm_state_header(fb);
 357     qemu_savevm_state_setup(fb);
 358     qemu_mutex_lock_iothread();
 359     qemu_savevm_state_complete_precopy(fb, false, false);
 360     qemu_mutex_unlock_iothread();
 361
 362     qemu_fflush(fb);
 363
 364     colo_send_message(s->to_dst_file, COLO_MESSAGE_VMSTATE_SEND, &local_err);
 365     if (local_err) {
 366         goto out;
 367     }
 368     /*
 369      * We need the size of the VMstate data in Secondary side,
 370      * With which we can decide how much data should be read.
 371      */
 372     colo_send_message_value(s->to_dst_file, COLO_MESSAGE_VMSTATE_SIZE,
 373                             bioc->usage, &local_err);
 374     if (local_err) {
 375         goto out;
 376     }
 377
 378     qemu_put_buffer(s->to_dst_file, bioc->data, bioc->usage);
 379     qemu_fflush(s->to_dst_file);
 380     ret = qemu_file_get_error(s->to_dst_file);
 381     if (ret < 0) {
 382         goto out;
 383     }
 384
 385     colo_receive_check_message(s->rp_state.from_dst_file,
 386                        COLO_MESSAGE_VMSTATE_RECEIVED, &local_err);
 387     if (local_err) {
 388         goto out;
 389     }
 390
 391     colo_receive_check_message(s->rp_state.from_dst_file,
 392                        COLO_MESSAGE_VMSTATE_LOADED, &local_err);
 393     if (local_err) {
 394         goto out;
 395     }
 396
 397     ret = 0;
 398
 399     qemu_mutex_lock_iothread();
 400     vm_start();
 401     qemu_mutex_unlock_iothread();
 402     trace_colo_vm_state_change("stop", "run");
 403
 404 out:
 405     if (local_err) {
 406         error_report_err(local_err);
 407     }
 408     return ret;
 409 }
 410
 411 static void colo_compare_notify_checkpoint(Notifier *notifier, void *data)
 412 {
 413     colo_checkpoint_notify(data);
 414 }
 415
 416 static void colo_process_checkpoint(MigrationState *s)
 417 {
 418     QIOChannelBuffer *bioc;
 419     QEMUFile *fb = NULL;
 420     int64_t current_time = qemu_clock_get_ms(QEMU_CLOCK_HOST);
 421     Error *local_err = NULL;
 422     int ret;
 423
 424     failover_init_state();
 425
 426     s->rp_state.from_dst_file = qemu_file_get_return_path(s->to_dst_file);
 427     if (!s->rp_state.from_dst_file) {
 428         error_report("Open QEMUFile from_dst_file failed");
 429         goto out;
 430     }
 431
 432     packets_compare_notifier.notify = colo_compare_notify_checkpoint;
 433     colo_compare_register_notifier(&packets_compare_notifier);
 434
 435     /*
 436      * Wait for Secondary finish loading VM states and enter COLO
 437      * restore.
 438      */
 439     colo_receive_check_message(s->rp_state.from_dst_file,
 440                        COLO_MESSAGE_CHECKPOINT_READY, &local_err);
 441     if (local_err) {
 442         goto out;
 443     }
 444     bioc = qio_channel_buffer_new(COLO_BUFFER_BASE_SIZE);
 445     fb = qemu_fopen_channel_output(QIO_CHANNEL(bioc));
 446     object_unref(OBJECT(bioc));
 447
 448     qemu_mutex_lock_iothread();
 449     vm_start();
 450     qemu_mutex_unlock_iothread();
 451     trace_colo_vm_state_change("stop", "run");
 452
 453     timer_mod(s->colo_delay_timer,
 454             current_time + s->parameters.x_checkpoint_delay);
 455
 456     while (s->state == MIGRATION_STATUS_COLO) {
 457         if (failover_get_state() != FAILOVER_STATUS_NONE) {
 458             error_report("failover request");
 459             goto out;
 460         }
 461
 462         qemu_sem_wait(&s->colo_checkpoint_sem);
 463
 464         ret = colo_do_checkpoint_transaction(s, bioc, fb);
 465         if (ret < 0) {
 466             goto out;
 467         }
 468     }
 469
 470 out:
 471     /* Throw the unreported error message after exited from loop */
 472     if (local_err) {
 473         error_report_err(local_err);
 474     }
 475
 476     if (fb) {
 477         qemu_fclose(fb);
 478     }
 479
 480     /* Hope this not to be too long to wait here */
 481     qemu_sem_wait(&s->colo_exit_sem);
 482     qemu_sem_destroy(&s->colo_exit_sem);
 483
 484     /*
 485      * It is safe to unregister notifier after failover finished.
 486      * Besides, colo_delay_timer and colo_checkpoint_sem can't be
 487      * released befor unregister notifier, or there will be use-after-free
 488      * error.
 489      */
 490     colo_compare_unregister_notifier(&packets_compare_notifier);
 491     timer_del(s->colo_delay_timer);
 492     timer_free(s->colo_delay_timer);
 493     qemu_sem_destroy(&s->colo_checkpoint_sem);
 494
 495     /*
 496      * Must be called after failover BH is completed,
 497      * Or the failover BH may shutdown the wrong fd that
 498      * re-used by other threads after we release here.
 499      */
 500     if (s->rp_state.from_dst_file) {
 501         qemu_fclose(s->rp_state.from_dst_file);
 502     }
 503 }
 504
 505 void colo_checkpoint_notify(void *opaque)
 506 {
 507     MigrationState *s = opaque;
 508     int64_t next_notify_time;
 509
 510     qemu_sem_post(&s->colo_checkpoint_sem);
 511     s->colo_checkpoint_time = qemu_clock_get_ms(QEMU_CLOCK_HOST);
 512     next_notify_time = s->colo_checkpoint_time +
 513                     s->parameters.x_checkpoint_delay;
 514     timer_mod(s->colo_delay_timer, next_notify_time);
 515 }
 516
 517 void migrate_start_colo_process(MigrationState *s)
 518 {
 519     qemu_mutex_unlock_iothread();
 520     qemu_sem_init(&s->colo_checkpoint_sem, 0);
 521     s->colo_delay_timer =  timer_new_ms(QEMU_CLOCK_HOST,
 522                                 colo_checkpoint_notify, s);
 523
 524     qemu_sem_init(&s->colo_exit_sem, 0);
 525     migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE,
 526                       MIGRATION_STATUS_COLO);
 527     colo_process_checkpoint(s);
 528     qemu_mutex_lock_iothread();
 529 }
 530
 531 static void colo_wait_handle_message(QEMUFile *f, int *checkpoint_request,
 532                                      Error **errp)
 533 {
 534     COLOMessage msg;
 535     Error *local_err = NULL;
 536
 537     msg = colo_receive_message(f, &local_err);
 538     if (local_err) {
 539         error_propagate(errp, local_err);
 540         return;
 541     }
 542
 543     switch (msg) {
 544     case COLO_MESSAGE_CHECKPOINT_REQUEST:
 545         *checkpoint_request = 1;
 546         break;
 547     default:
 548         *checkpoint_request = 0;
 549         error_setg(errp, "Got unknown COLO message: %d", msg);
 550         break;
 551     }
 552 }
 553
 554 void *colo_process_incoming_thread(void *opaque)
 555 {
 556     MigrationIncomingState *mis = opaque;
 557     QEMUFile *fb = NULL;
 558     QIOChannelBuffer *bioc = NULL; /* Cache incoming device state */
 559     uint64_t total_size;
 560     uint64_t value;
 561     Error *local_err = NULL;
 562
 563     rcu_register_thread();
 564     qemu_sem_init(&mis->colo_incoming_sem, 0);
 565
 566     migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
 567                       MIGRATION_STATUS_COLO);
 568
 569     failover_init_state();
 570
 571     mis->to_src_file = qemu_file_get_return_path(mis->from_src_file);
 572     if (!mis->to_src_file) {
 573         error_report("COLO incoming thread: Open QEMUFile to_src_file failed");
 574         goto out;
 575     }
 576     /*
 577      * Note: the communication between Primary side and Secondary side
 578      * should be sequential, we set the fd to unblocked in migration incoming
 579      * coroutine, and here we are in the COLO incoming thread, so it is ok to
 580      * set the fd back to blocked.
 581      */
 582     qemu_file_set_blocking(mis->from_src_file, true);
 583
 584     bioc = qio_channel_buffer_new(COLO_BUFFER_BASE_SIZE);
 585     fb = qemu_fopen_channel_input(QIO_CHANNEL(bioc));
 586     object_unref(OBJECT(bioc));
 587
 588     qemu_mutex_lock_iothread();
 589     vm_start();
 590     trace_colo_vm_state_change("stop", "run");
 591     qemu_mutex_unlock_iothread();
 592
 593     colo_send_message(mis->to_src_file, COLO_MESSAGE_CHECKPOINT_READY,
 594                       &local_err);
 595     if (local_err) {
 596         goto out;
 597     }
 598
 599     while (mis->state == MIGRATION_STATUS_COLO) {
 600         int request = 0;
 601
 602         colo_wait_handle_message(mis->from_src_file, &request, &local_err);
 603         if (local_err) {
 604             goto out;
 605         }
 606         assert(request);
 607         if (failover_get_state() != FAILOVER_STATUS_NONE) {
 608             error_report("failover request");
 609             goto out;
 610         }
 611
 612         qemu_mutex_lock_iothread();
 613         vm_stop_force_state(RUN_STATE_COLO);
 614         trace_colo_vm_state_change("run", "stop");
 615         qemu_mutex_unlock_iothread();
 616
 617         /* FIXME: This is unnecessary for periodic checkpoint mode */
 618         colo_send_message(mis->to_src_file, COLO_MESSAGE_CHECKPOINT_REPLY,
 619                      &local_err);
 620         if (local_err) {
 621             goto out;
 622         }
 623
 624         colo_receive_check_message(mis->from_src_file,
 625                            COLO_MESSAGE_VMSTATE_SEND, &local_err);
 626         if (local_err) {
 627             goto out;
 628         }
 629
 630         value = colo_receive_message_value(mis->from_src_file,
 631                                  COLO_MESSAGE_VMSTATE_SIZE, &local_err);
 632         if (local_err) {
 633             goto out;
 634         }
 635
 636         /*
 637          * Read VM device state data into channel buffer,
 638          * It's better to re-use the memory allocated.
 639          * Here we need to handle the channel buffer directly.
 640          */
 641         if (value > bioc->capacity) {
 642             bioc->capacity = value;
 643             bioc->data = g_realloc(bioc->data, bioc->capacity);
 644         }
 645         total_size = qemu_get_buffer(mis->from_src_file, bioc->data, value);
 646         if (total_size != value) {
 647             error_report("Got %" PRIu64 " VMState data, less than expected"
 648                         " %" PRIu64, total_size, value);
 649             goto out;
 650         }
 651         bioc->usage = total_size;
 652         qio_channel_io_seek(QIO_CHANNEL(bioc), 0, 0, NULL);
 653
 654         colo_send_message(mis->to_src_file, COLO_MESSAGE_VMSTATE_RECEIVED,
 655                      &local_err);
 656         if (local_err) {
 657             goto out;
 658         }
 659
 660         qemu_mutex_lock_iothread();
 661         qemu_system_reset(SHUTDOWN_CAUSE_NONE);
 662         vmstate_loading = true;
 663         if (qemu_loadvm_state(fb) < 0) {
 664             error_report("COLO: loadvm failed");
 665             qemu_mutex_unlock_iothread();
 666             goto out;
 667         }
 668
 669         vmstate_loading = false;
 670         vm_start();
 671         trace_colo_vm_state_change("stop", "run");
 672         qemu_mutex_unlock_iothread();
 673
 674         if (failover_get_state() == FAILOVER_STATUS_RELAUNCH) {
 675             failover_set_state(FAILOVER_STATUS_RELAUNCH,
 676                             FAILOVER_STATUS_NONE);
 677             failover_request_active(NULL);
 678             goto out;
 679         }
 680
 681         colo_send_message(mis->to_src_file, COLO_MESSAGE_VMSTATE_LOADED,
 682                      &local_err);
 683         if (local_err) {
 684             goto out;
 685         }
 686     }
 687
 688 out:
 689     vmstate_loading = false;
 690     /* Throw the unreported error message after exited from loop */
 691     if (local_err) {
 692         error_report_err(local_err);
 693     }
 694
 695     if (fb) {
 696         qemu_fclose(fb);
 697     }
 698
 699     /* Hope this not to be too long to loop here */
 700     qemu_sem_wait(&mis->colo_incoming_sem);
 701     qemu_sem_destroy(&mis->colo_incoming_sem);
 702     /* Must be called after failover BH is completed */
 703     if (mis->to_src_file) {
 704         qemu_fclose(mis->to_src_file);
 705     }
 706     migration_incoming_exit_colo();
 707
 708     rcu_unregister_thread();
 709     return NULL;
 710 }