qemu-timer.c

   1 /*
   2  * QEMU System Emulator
   3  *
   4  * Copyright (c) 2003-2008 Fabrice Bellard
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24
  25 #include "sysemu.h"
  26 #include "net.h"
  27 #include "monitor.h"
  28 #include "console.h"
  29
  30 #include "hw/hw.h"
  31
  32 #include "qemu-timer.h"
  33
  34 #ifdef __FreeBSD__
  35 #include <sys/param.h>
  36 #endif
  37
  38 #ifdef _WIN32
  39 #include <mmsystem.h>
  40 #endif
  41
  42 /***********************************************************/
  43 /* timers */
  44
  45 #define QEMU_CLOCK_REALTIME 0
  46 #define QEMU_CLOCK_VIRTUAL  1
  47 #define QEMU_CLOCK_HOST     2
  48
  49 struct QEMUClock {
  50     int type;
  51     bool enabled;
  52
  53     QEMUTimer *active_timers;
  54
  55     NotifierList reset_notifiers;
  56     int64_t last;
  57 };
  58
  59 struct QEMUTimer {
  60     QEMUClock *clock;
  61     int64_t expire_time;        /* in nanoseconds */
  62     int scale;
  63     QEMUTimerCB *cb;
  64     void *opaque;
  65     struct QEMUTimer *next;
  66 };
  67
  68 struct qemu_alarm_timer {
  69     char const *name;
  70     int (*start)(struct qemu_alarm_timer *t);
  71     void (*stop)(struct qemu_alarm_timer *t);
  72     void (*rearm)(struct qemu_alarm_timer *t, int64_t nearest_delta_ns);
  73 #if defined(__linux__)
  74     int fd;
  75     timer_t timer;
  76 #elif defined(_WIN32)
  77     HANDLE timer;
  78 #endif
  79     bool expired;
  80     bool pending;
  81 };
  82
  83 static struct qemu_alarm_timer *alarm_timer;
  84
  85 static bool qemu_timer_expired_ns(QEMUTimer *timer_head, int64_t current_time)
  86 {
  87     return timer_head && (timer_head->expire_time <= current_time);
  88 }
  89
  90 static inline int alarm_has_dynticks(struct qemu_alarm_timer *t)
  91 {
  92     return !!t->rearm;
  93 }
  94
  95 static int64_t qemu_next_alarm_deadline(void)
  96 {
  97     int64_t delta = INT64_MAX;
  98     int64_t rtdelta;
  99
 100     if (!use_icount && vm_clock->enabled && vm_clock->active_timers) {
 101         delta = vm_clock->active_timers->expire_time -
 102                      qemu_get_clock_ns(vm_clock);
 103     }
 104     if (host_clock->enabled && host_clock->active_timers) {
 105         int64_t hdelta = host_clock->active_timers->expire_time -
 106                  qemu_get_clock_ns(host_clock);
 107         if (hdelta < delta) {
 108             delta = hdelta;
 109         }
 110     }
 111     if (rt_clock->enabled && rt_clock->active_timers) {
 112         rtdelta = (rt_clock->active_timers->expire_time -
 113                  qemu_get_clock_ns(rt_clock));
 114         if (rtdelta < delta) {
 115             delta = rtdelta;
 116         }
 117     }
 118
 119     return delta;
 120 }
 121
 122 static void qemu_rearm_alarm_timer(struct qemu_alarm_timer *t)
 123 {
 124     int64_t nearest_delta_ns;
 125     assert(alarm_has_dynticks(t));
 126     if (!rt_clock->active_timers &&
 127         !vm_clock->active_timers &&
 128         !host_clock->active_timers) {
 129         return;
 130     }
 131     nearest_delta_ns = qemu_next_alarm_deadline();
 132     t->rearm(t, nearest_delta_ns);
 133 }
 134
 135 /* TODO: MIN_TIMER_REARM_NS should be optimized */
 136 #define MIN_TIMER_REARM_NS 250000
 137
 138 #ifdef _WIN32
 139
 140 static int mm_start_timer(struct qemu_alarm_timer *t);
 141 static void mm_stop_timer(struct qemu_alarm_timer *t);
 142 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 143
 144 static int win32_start_timer(struct qemu_alarm_timer *t);
 145 static void win32_stop_timer(struct qemu_alarm_timer *t);
 146 static void win32_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 147
 148 #else
 149
 150 static int unix_start_timer(struct qemu_alarm_timer *t);
 151 static void unix_stop_timer(struct qemu_alarm_timer *t);
 152 static void unix_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 153
 154 #ifdef __linux__
 155
 156 static int dynticks_start_timer(struct qemu_alarm_timer *t);
 157 static void dynticks_stop_timer(struct qemu_alarm_timer *t);
 158 static void dynticks_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 159
 160 #endif /* __linux__ */
 161
 162 #endif /* _WIN32 */
 163
 164 static struct qemu_alarm_timer alarm_timers[] = {
 165 #ifndef _WIN32
 166 #ifdef __linux__
 167     {"dynticks", dynticks_start_timer,
 168      dynticks_stop_timer, dynticks_rearm_timer},
 169 #endif
 170     {"unix", unix_start_timer, unix_stop_timer, unix_rearm_timer},
 171 #else
 172     {"mmtimer", mm_start_timer, mm_stop_timer, mm_rearm_timer},
 173     {"dynticks", win32_start_timer, win32_stop_timer, win32_rearm_timer},
 174 #endif
 175     {NULL, }
 176 };
 177
 178 static void show_available_alarms(void)
 179 {
 180     int i;
 181
 182     printf("Available alarm timers, in order of precedence:\n");
 183     for (i = 0; alarm_timers[i].name; i++)
 184         printf("%s\n", alarm_timers[i].name);
 185 }
 186
 187 void configure_alarms(char const *opt)
 188 {
 189     int i;
 190     int cur = 0;
 191     int count = ARRAY_SIZE(alarm_timers) - 1;
 192     char *arg;
 193     char *name;
 194     struct qemu_alarm_timer tmp;
 195
 196     if (!strcmp(opt, "?")) {
 197         show_available_alarms();
 198         exit(0);
 199     }
 200
 201     arg = g_strdup(opt);
 202
 203     /* Reorder the array */
 204     name = strtok(arg, ",");
 205     while (name) {
 206         for (i = 0; i < count && alarm_timers[i].name; i++) {
 207             if (!strcmp(alarm_timers[i].name, name))
 208                 break;
 209         }
 210
 211         if (i == count) {
 212             fprintf(stderr, "Unknown clock %s\n", name);
 213             goto next;
 214         }
 215
 216         if (i < cur)
 217             /* Ignore */
 218             goto next;
 219
 220         /* Swap */
 221         tmp = alarm_timers[i];
 222         alarm_timers[i] = alarm_timers[cur];
 223         alarm_timers[cur] = tmp;
 224
 225         cur++;
 226 next:
 227         name = strtok(NULL, ",");
 228     }
 229
 230     g_free(arg);
 231
 232     if (cur) {
 233         /* Disable remaining timers */
 234         for (i = cur; i < count; i++)
 235             alarm_timers[i].name = NULL;
 236     } else {
 237         show_available_alarms();
 238         exit(1);
 239     }
 240 }
 241
 242 QEMUClock *rt_clock;
 243 QEMUClock *vm_clock;
 244 QEMUClock *host_clock;
 245
 246 static QEMUClock *qemu_new_clock(int type)
 247 {
 248     QEMUClock *clock;
 249
 250     clock = g_malloc0(sizeof(QEMUClock));
 251     clock->type = type;
 252     clock->enabled = true;
 253     clock->last = INT64_MIN;
 254     notifier_list_init(&clock->reset_notifiers);
 255     return clock;
 256 }
 257
 258 void qemu_clock_enable(QEMUClock *clock, bool enabled)
 259 {
 260     bool old = clock->enabled;
 261     clock->enabled = enabled;
 262     if (enabled && !old) {
 263         qemu_rearm_alarm_timer(alarm_timer);
 264     }
 265 }
 266
 267 int64_t qemu_clock_has_timers(QEMUClock *clock)
 268 {
 269     return !!clock->active_timers;
 270 }
 271
 272 int64_t qemu_clock_expired(QEMUClock *clock)
 273 {
 274     return (clock->active_timers &&
 275             clock->active_timers->expire_time < qemu_get_clock_ns(clock));
 276 }
 277
 278 int64_t qemu_clock_deadline(QEMUClock *clock)
 279 {
 280     /* To avoid problems with overflow limit this to 2^32.  */
 281     int64_t delta = INT32_MAX;
 282
 283     if (clock->active_timers) {
 284         delta = clock->active_timers->expire_time - qemu_get_clock_ns(clock);
 285     }
 286     if (delta < 0) {
 287         delta = 0;
 288     }
 289     return delta;
 290 }
 291
 292 QEMUTimer *qemu_new_timer(QEMUClock *clock, int scale,
 293                           QEMUTimerCB *cb, void *opaque)
 294 {
 295     QEMUTimer *ts;
 296
 297     ts = g_malloc0(sizeof(QEMUTimer));
 298     ts->clock = clock;
 299     ts->cb = cb;
 300     ts->opaque = opaque;
 301     ts->scale = scale;
 302     return ts;
 303 }
 304
 305 void qemu_free_timer(QEMUTimer *ts)
 306 {
 307     g_free(ts);
 308 }
 309
 310 /* stop a timer, but do not dealloc it */
 311 void qemu_del_timer(QEMUTimer *ts)
 312 {
 313     QEMUTimer **pt, *t;
 314
 315     /* NOTE: this code must be signal safe because
 316        qemu_timer_expired() can be called from a signal. */
 317     pt = &ts->clock->active_timers;
 318     for(;;) {
 319         t = *pt;
 320         if (!t)
 321             break;
 322         if (t == ts) {
 323             *pt = t->next;
 324             break;
 325         }
 326         pt = &t->next;
 327     }
 328 }
 329
 330 /* modify the current timer so that it will be fired when current_time
 331    >= expire_time. The corresponding callback will be called. */
 332 void qemu_mod_timer_ns(QEMUTimer *ts, int64_t expire_time)
 333 {
 334     QEMUTimer **pt, *t;
 335
 336     qemu_del_timer(ts);
 337
 338     /* add the timer in the sorted list */
 339     /* NOTE: this code must be signal safe because
 340        qemu_timer_expired() can be called from a signal. */
 341     pt = &ts->clock->active_timers;
 342     for(;;) {
 343         t = *pt;
 344         if (!qemu_timer_expired_ns(t, expire_time)) {
 345             break;
 346         }
 347         pt = &t->next;
 348     }
 349     ts->expire_time = expire_time;
 350     ts->next = *pt;
 351     *pt = ts;
 352
 353     /* Rearm if necessary  */
 354     if (pt == &ts->clock->active_timers) {
 355         if (!alarm_timer->pending) {
 356             qemu_rearm_alarm_timer(alarm_timer);
 357         }
 358         /* Interrupt execution to force deadline recalculation.  */
 359         qemu_clock_warp(ts->clock);
 360         if (use_icount) {
 361             qemu_notify_event();
 362         }
 363     }
 364 }
 365
 366 void qemu_mod_timer(QEMUTimer *ts, int64_t expire_time)
 367 {
 368     qemu_mod_timer_ns(ts, expire_time * ts->scale);
 369 }
 370
 371 bool qemu_timer_pending(QEMUTimer *ts)
 372 {
 373     QEMUTimer *t;
 374     for (t = ts->clock->active_timers; t != NULL; t = t->next) {
 375         if (t == ts) {
 376             return true;
 377         }
 378     }
 379     return false;
 380 }
 381
 382 bool qemu_timer_expired(QEMUTimer *timer_head, int64_t current_time)
 383 {
 384     return qemu_timer_expired_ns(timer_head, current_time * timer_head->scale);
 385 }
 386
 387 void qemu_run_timers(QEMUClock *clock)
 388 {
 389     QEMUTimer **ptimer_head, *ts;
 390     int64_t current_time;
 391
 392     if (!clock->enabled)
 393         return;
 394
 395     current_time = qemu_get_clock_ns(clock);
 396     ptimer_head = &clock->active_timers;
 397     for(;;) {
 398         ts = *ptimer_head;
 399         if (!qemu_timer_expired_ns(ts, current_time)) {
 400             break;
 401         }
 402         /* remove timer from the list before calling the callback */
 403         *ptimer_head = ts->next;
 404         ts->next = NULL;
 405
 406         /* run the callback (the timer list can be modified) */
 407         ts->cb(ts->opaque);
 408     }
 409 }
 410
 411 int64_t qemu_get_clock_ns(QEMUClock *clock)
 412 {
 413     int64_t now, last;
 414
 415     switch(clock->type) {
 416     case QEMU_CLOCK_REALTIME:
 417         return get_clock();
 418     default:
 419     case QEMU_CLOCK_VIRTUAL:
 420         if (use_icount) {
 421             return cpu_get_icount();
 422         } else {
 423             return cpu_get_clock();
 424         }
 425     case QEMU_CLOCK_HOST:
 426         now = get_clock_realtime();
 427         last = clock->last;
 428         clock->last = now;
 429         if (now < last) {
 430             notifier_list_notify(&clock->reset_notifiers, &now);
 431         }
 432         return now;
 433     }
 434 }
 435
 436 void qemu_register_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 437 {
 438     notifier_list_add(&clock->reset_notifiers, notifier);
 439 }
 440
 441 void qemu_unregister_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 442 {
 443     notifier_remove(notifier);
 444 }
 445
 446 void init_clocks(void)
 447 {
 448     rt_clock = qemu_new_clock(QEMU_CLOCK_REALTIME);
 449     vm_clock = qemu_new_clock(QEMU_CLOCK_VIRTUAL);
 450     host_clock = qemu_new_clock(QEMU_CLOCK_HOST);
 451 }
 452
 453 uint64_t qemu_timer_expire_time_ns(QEMUTimer *ts)
 454 {
 455     return qemu_timer_pending(ts) ? ts->expire_time : -1;
 456 }
 457
 458 void qemu_run_all_timers(void)
 459 {
 460     alarm_timer->pending = false;
 461
 462     /* vm time timers */
 463     qemu_run_timers(vm_clock);
 464     qemu_run_timers(rt_clock);
 465     qemu_run_timers(host_clock);
 466
 467     /* rearm timer, if not periodic */
 468     if (alarm_timer->expired) {
 469         alarm_timer->expired = false;
 470         qemu_rearm_alarm_timer(alarm_timer);
 471     }
 472 }
 473
 474 #ifdef _WIN32
 475 static void CALLBACK host_alarm_handler(PVOID lpParam, BOOLEAN unused)
 476 #else
 477 static void host_alarm_handler(int host_signum)
 478 #endif
 479 {
 480     struct qemu_alarm_timer *t = alarm_timer;
 481     if (!t)
 482         return;
 483
 484     if (alarm_has_dynticks(t) ||
 485         qemu_next_alarm_deadline () <= 0) {
 486         t->expired = alarm_has_dynticks(t);
 487         t->pending = true;
 488         qemu_notify_event();
 489     }
 490 }
 491
 492 #if defined(__linux__)
 493
 494 #include "compatfd.h"
 495
 496 static int dynticks_start_timer(struct qemu_alarm_timer *t)
 497 {
 498     struct sigevent ev;
 499     timer_t host_timer;
 500     struct sigaction act;
 501
 502     sigfillset(&act.sa_mask);
 503     act.sa_flags = 0;
 504     act.sa_handler = host_alarm_handler;
 505
 506     sigaction(SIGALRM, &act, NULL);
 507
 508     /*
 509      * Initialize ev struct to 0 to avoid valgrind complaining
 510      * about uninitialized data in timer_create call
 511      */
 512     memset(&ev, 0, sizeof(ev));
 513     ev.sigev_value.sival_int = 0;
 514     ev.sigev_notify = SIGEV_SIGNAL;
 515 #ifdef SIGEV_THREAD_ID
 516     if (qemu_signalfd_available()) {
 517         ev.sigev_notify = SIGEV_THREAD_ID;
 518         ev._sigev_un._tid = qemu_get_thread_id();
 519     }
 520 #endif /* SIGEV_THREAD_ID */
 521     ev.sigev_signo = SIGALRM;
 522
 523     if (timer_create(CLOCK_REALTIME, &ev, &host_timer)) {
 524         perror("timer_create");
 525
 526         /* disable dynticks */
 527         fprintf(stderr, "Dynamic Ticks disabled\n");
 528
 529         return -1;
 530     }
 531
 532     t->timer = host_timer;
 533
 534     return 0;
 535 }
 536
 537 static void dynticks_stop_timer(struct qemu_alarm_timer *t)
 538 {
 539     timer_t host_timer = t->timer;
 540
 541     timer_delete(host_timer);
 542 }
 543
 544 static void dynticks_rearm_timer(struct qemu_alarm_timer *t,
 545                                  int64_t nearest_delta_ns)
 546 {
 547     timer_t host_timer = t->timer;
 548     struct itimerspec timeout;
 549     int64_t current_ns;
 550
 551     if (nearest_delta_ns < MIN_TIMER_REARM_NS)
 552         nearest_delta_ns = MIN_TIMER_REARM_NS;
 553
 554     /* check whether a timer is already running */
 555     if (timer_gettime(host_timer, &timeout)) {
 556         perror("gettime");
 557         fprintf(stderr, "Internal timer error: aborting\n");
 558         exit(1);
 559     }
 560     current_ns = timeout.it_value.tv_sec * 1000000000LL + timeout.it_value.tv_nsec;
 561     if (current_ns && current_ns <= nearest_delta_ns)
 562         return;
 563
 564     timeout.it_interval.tv_sec = 0;
 565     timeout.it_interval.tv_nsec = 0; /* 0 for one-shot timer */
 566     timeout.it_value.tv_sec =  nearest_delta_ns / 1000000000;
 567     timeout.it_value.tv_nsec = nearest_delta_ns % 1000000000;
 568     if (timer_settime(host_timer, 0 /* RELATIVE */, &timeout, NULL)) {
 569         perror("settime");
 570         fprintf(stderr, "Internal timer error: aborting\n");
 571         exit(1);
 572     }
 573 }
 574
 575 #endif /* defined(__linux__) */
 576
 577 #if !defined(_WIN32)
 578
 579 static int unix_start_timer(struct qemu_alarm_timer *t)
 580 {
 581     struct sigaction act;
 582
 583     /* timer signal */
 584     sigfillset(&act.sa_mask);
 585     act.sa_flags = 0;
 586     act.sa_handler = host_alarm_handler;
 587
 588     sigaction(SIGALRM, &act, NULL);
 589     return 0;
 590 }
 591
 592 static void unix_rearm_timer(struct qemu_alarm_timer *t,
 593                              int64_t nearest_delta_ns)
 594 {
 595     struct itimerval itv;
 596     int err;
 597
 598     if (nearest_delta_ns < MIN_TIMER_REARM_NS)
 599         nearest_delta_ns = MIN_TIMER_REARM_NS;
 600
 601     itv.it_interval.tv_sec = 0;
 602     itv.it_interval.tv_usec = 0; /* 0 for one-shot timer */
 603     itv.it_value.tv_sec =  nearest_delta_ns / 1000000000;
 604     itv.it_value.tv_usec = (nearest_delta_ns % 1000000000) / 1000;
 605     err = setitimer(ITIMER_REAL, &itv, NULL);
 606     if (err) {
 607         perror("setitimer");
 608         fprintf(stderr, "Internal timer error: aborting\n");
 609         exit(1);
 610     }
 611 }
 612
 613 static void unix_stop_timer(struct qemu_alarm_timer *t)
 614 {
 615     struct itimerval itv;
 616
 617     memset(&itv, 0, sizeof(itv));
 618     setitimer(ITIMER_REAL, &itv, NULL);
 619 }
 620
 621 #endif /* !defined(_WIN32) */
 622
 623
 624 #ifdef _WIN32
 625
 626 static MMRESULT mm_timer;
 627 static unsigned mm_period;
 628
 629 static void CALLBACK mm_alarm_handler(UINT uTimerID, UINT uMsg,
 630                                       DWORD_PTR dwUser, DWORD_PTR dw1,
 631                                       DWORD_PTR dw2)
 632 {
 633     struct qemu_alarm_timer *t = alarm_timer;
 634     if (!t) {
 635         return;
 636     }
 637     if (alarm_has_dynticks(t) || qemu_next_alarm_deadline() <= 0) {
 638         t->expired = alarm_has_dynticks(t);
 639         t->pending = true;
 640         qemu_notify_event();
 641     }
 642 }
 643
 644 static int mm_start_timer(struct qemu_alarm_timer *t)
 645 {
 646     TIMECAPS tc;
 647     UINT flags;
 648
 649     memset(&tc, 0, sizeof(tc));
 650     timeGetDevCaps(&tc, sizeof(tc));
 651
 652     mm_period = tc.wPeriodMin;
 653     timeBeginPeriod(mm_period);
 654
 655     flags = TIME_CALLBACK_FUNCTION;
 656     if (alarm_has_dynticks(t)) {
 657         flags |= TIME_ONESHOT;
 658     } else {
 659         flags |= TIME_PERIODIC;
 660     }
 661
 662     mm_timer = timeSetEvent(1,                  /* interval (ms) */
 663                             mm_period,          /* resolution */
 664                             mm_alarm_handler,   /* function */
 665                             (DWORD_PTR)t,       /* parameter */
 666                             flags);
 667
 668     if (!mm_timer) {
 669         fprintf(stderr, "Failed to initialize win32 alarm timer: %ld\n",
 670                 GetLastError());
 671         timeEndPeriod(mm_period);
 672         return -1;
 673     }
 674
 675     return 0;
 676 }
 677
 678 static void mm_stop_timer(struct qemu_alarm_timer *t)
 679 {
 680     timeKillEvent(mm_timer);
 681     timeEndPeriod(mm_period);
 682 }
 683
 684 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta)
 685 {
 686     int64_t nearest_delta_ms = delta / 1000000;
 687     if (nearest_delta_ms < 1) {
 688         nearest_delta_ms = 1;
 689     }
 690     /* UINT_MAX can be 32 bit */
 691     if (nearest_delta_ms > UINT_MAX) {
 692         nearest_delta_ms = UINT_MAX;
 693     }
 694
 695     timeKillEvent(mm_timer);
 696     mm_timer = timeSetEvent((unsigned int) nearest_delta_ms,
 697                             mm_period,
 698                             mm_alarm_handler,
 699                             (DWORD_PTR)t,
 700                             TIME_ONESHOT | TIME_CALLBACK_FUNCTION);
 701
 702     if (!mm_timer) {
 703         fprintf(stderr, "Failed to re-arm win32 alarm timer %ld\n",
 704                 GetLastError());
 705
 706         timeEndPeriod(mm_period);
 707         exit(1);
 708     }
 709 }
 710
 711 static int win32_start_timer(struct qemu_alarm_timer *t)
 712 {
 713     HANDLE hTimer;
 714     BOOLEAN success;
 715
 716     /* If you call ChangeTimerQueueTimer on a one-shot timer (its period
 717        is zero) that has already expired, the timer is not updated.  Since
 718        creating a new timer is relatively expensive, set a bogus one-hour
 719        interval in the dynticks case.  */
 720     success = CreateTimerQueueTimer(&hTimer,
 721                           NULL,
 722                           host_alarm_handler,
 723                           t,
 724                           1,
 725                           alarm_has_dynticks(t) ? 3600000 : 1,
 726                           WT_EXECUTEINTIMERTHREAD);
 727
 728     if (!success) {
 729         fprintf(stderr, "Failed to initialize win32 alarm timer: %ld\n",
 730                 GetLastError());
 731         return -1;
 732     }
 733
 734     t->timer = hTimer;
 735     return 0;
 736 }
 737
 738 static void win32_stop_timer(struct qemu_alarm_timer *t)
 739 {
 740     HANDLE hTimer = t->timer;
 741
 742     if (hTimer) {
 743         DeleteTimerQueueTimer(NULL, hTimer, NULL);
 744     }
 745 }
 746
 747 static void win32_rearm_timer(struct qemu_alarm_timer *t,
 748                               int64_t nearest_delta_ns)
 749 {
 750     HANDLE hTimer = t->timer;
 751     int64_t nearest_delta_ms;
 752     BOOLEAN success;
 753
 754     nearest_delta_ms = nearest_delta_ns / 1000000;
 755     if (nearest_delta_ms < 1) {
 756         nearest_delta_ms = 1;
 757     }
 758     /* ULONG_MAX can be 32 bit */
 759     if (nearest_delta_ms > ULONG_MAX) {
 760         nearest_delta_ms = ULONG_MAX;
 761     }
 762     success = ChangeTimerQueueTimer(NULL,
 763                                     hTimer,
 764                                     (unsigned long) nearest_delta_ms,
 765                                     3600000);
 766
 767     if (!success) {
 768         fprintf(stderr, "Failed to rearm win32 alarm timer: %ld\n",
 769                 GetLastError());
 770         exit(-1);
 771     }
 772
 773 }
 774
 775 #endif /* _WIN32 */
 776
 777 static void quit_timers(void)
 778 {
 779     struct qemu_alarm_timer *t = alarm_timer;
 780     alarm_timer = NULL;
 781     t->stop(t);
 782 }
 783
 784 int init_timer_alarm(void)
 785 {
 786     struct qemu_alarm_timer *t = NULL;
 787     int i, err = -1;
 788
 789     for (i = 0; alarm_timers[i].name; i++) {
 790         t = &alarm_timers[i];
 791
 792         err = t->start(t);
 793         if (!err)
 794             break;
 795     }
 796
 797     if (err) {
 798         err = -ENOENT;
 799         goto fail;
 800     }
 801
 802     /* first event is at time 0 */
 803     atexit(quit_timers);
 804     t->pending = true;
 805     alarm_timer = t;
 806
 807     return 0;
 808
 809 fail:
 810     return err;
 811 }
 812