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 <unistd.h>
  33 #include <fcntl.h>
  34 #include <time.h>
  35 #include <errno.h>
  36 #include <sys/time.h>
  37 #include <signal.h>
  38 #ifdef __FreeBSD__
  39 #include <sys/param.h>
  40 #endif
  41
  42 #ifdef _WIN32
  43 #include <windows.h>
  44 #include <mmsystem.h>
  45 #endif
  46
  47 #include "qemu-timer.h"
  48
  49 /***********************************************************/
  50 /* timers */
  51
  52 #define QEMU_CLOCK_REALTIME 0
  53 #define QEMU_CLOCK_VIRTUAL  1
  54 #define QEMU_CLOCK_HOST     2
  55
  56 struct QEMUClock {
  57     int type;
  58     int enabled;
  59
  60     QEMUTimer *active_timers;
  61
  62     NotifierList reset_notifiers;
  63     int64_t last;
  64 };
  65
  66 struct QEMUTimer {
  67     QEMUClock *clock;
  68     int64_t expire_time;        /* in nanoseconds */
  69     int scale;
  70     QEMUTimerCB *cb;
  71     void *opaque;
  72     struct QEMUTimer *next;
  73 };
  74
  75 struct qemu_alarm_timer {
  76     char const *name;
  77     int (*start)(struct qemu_alarm_timer *t);
  78     void (*stop)(struct qemu_alarm_timer *t);
  79     void (*rearm)(struct qemu_alarm_timer *t, int64_t nearest_delta_ns);
  80 #if defined(__linux__)
  81     int fd;
  82     timer_t timer;
  83 #elif defined(_WIN32)
  84     HANDLE timer;
  85 #endif
  86     char expired;
  87     char pending;
  88 };
  89
  90 static struct qemu_alarm_timer *alarm_timer;
  91
  92 static bool qemu_timer_expired_ns(QEMUTimer *timer_head, int64_t current_time)
  93 {
  94     return timer_head && (timer_head->expire_time <= current_time);
  95 }
  96
  97 int qemu_alarm_pending(void)
  98 {
  99     return alarm_timer->pending;
 100 }
 101
 102 static inline int alarm_has_dynticks(struct qemu_alarm_timer *t)
 103 {
 104     return !!t->rearm;
 105 }
 106
 107 static int64_t qemu_next_alarm_deadline(void)
 108 {
 109     int64_t delta;
 110     int64_t rtdelta;
 111
 112     if (!use_icount && vm_clock->active_timers) {
 113         delta = vm_clock->active_timers->expire_time -
 114                      qemu_get_clock_ns(vm_clock);
 115     } else {
 116         delta = INT32_MAX;
 117     }
 118     if (host_clock->active_timers) {
 119         int64_t hdelta = host_clock->active_timers->expire_time -
 120                  qemu_get_clock_ns(host_clock);
 121         if (hdelta < delta) {
 122             delta = hdelta;
 123         }
 124     }
 125     if (rt_clock->active_timers) {
 126         rtdelta = (rt_clock->active_timers->expire_time -
 127                  qemu_get_clock_ns(rt_clock));
 128         if (rtdelta < delta) {
 129             delta = rtdelta;
 130         }
 131     }
 132
 133     return delta;
 134 }
 135
 136 static void qemu_rearm_alarm_timer(struct qemu_alarm_timer *t)
 137 {
 138     int64_t nearest_delta_ns;
 139     assert(alarm_has_dynticks(t));
 140     if (!rt_clock->active_timers &&
 141         !vm_clock->active_timers &&
 142         !host_clock->active_timers) {
 143         return;
 144     }
 145     nearest_delta_ns = qemu_next_alarm_deadline();
 146     t->rearm(t, nearest_delta_ns);
 147 }
 148
 149 /* TODO: MIN_TIMER_REARM_NS should be optimized */
 150 #define MIN_TIMER_REARM_NS 250000
 151
 152 #ifdef _WIN32
 153
 154 static int mm_start_timer(struct qemu_alarm_timer *t);
 155 static void mm_stop_timer(struct qemu_alarm_timer *t);
 156 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 157
 158 static int win32_start_timer(struct qemu_alarm_timer *t);
 159 static void win32_stop_timer(struct qemu_alarm_timer *t);
 160 static void win32_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 161
 162 #else
 163
 164 static int unix_start_timer(struct qemu_alarm_timer *t);
 165 static void unix_stop_timer(struct qemu_alarm_timer *t);
 166 static void unix_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 167
 168 #ifdef __linux__
 169
 170 static int dynticks_start_timer(struct qemu_alarm_timer *t);
 171 static void dynticks_stop_timer(struct qemu_alarm_timer *t);
 172 static void dynticks_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 173
 174 #endif /* __linux__ */
 175
 176 #endif /* _WIN32 */
 177
 178 static struct qemu_alarm_timer alarm_timers[] = {
 179 #ifndef _WIN32
 180 #ifdef __linux__
 181     {"dynticks", dynticks_start_timer,
 182      dynticks_stop_timer, dynticks_rearm_timer},
 183 #endif
 184     {"unix", unix_start_timer, unix_stop_timer, unix_rearm_timer},
 185 #else
 186     {"mmtimer", mm_start_timer, mm_stop_timer, mm_rearm_timer},
 187     {"dynticks", win32_start_timer, win32_stop_timer, win32_rearm_timer},
 188 #endif
 189     {NULL, }
 190 };
 191
 192 static void show_available_alarms(void)
 193 {
 194     int i;
 195
 196     printf("Available alarm timers, in order of precedence:\n");
 197     for (i = 0; alarm_timers[i].name; i++)
 198         printf("%s\n", alarm_timers[i].name);
 199 }
 200
 201 void configure_alarms(char const *opt)
 202 {
 203     int i;
 204     int cur = 0;
 205     int count = ARRAY_SIZE(alarm_timers) - 1;
 206     char *arg;
 207     char *name;
 208     struct qemu_alarm_timer tmp;
 209
 210     if (!strcmp(opt, "?")) {
 211         show_available_alarms();
 212         exit(0);
 213     }
 214
 215     arg = g_strdup(opt);
 216
 217     /* Reorder the array */
 218     name = strtok(arg, ",");
 219     while (name) {
 220         for (i = 0; i < count && alarm_timers[i].name; i++) {
 221             if (!strcmp(alarm_timers[i].name, name))
 222                 break;
 223         }
 224
 225         if (i == count) {
 226             fprintf(stderr, "Unknown clock %s\n", name);
 227             goto next;
 228         }
 229
 230         if (i < cur)
 231             /* Ignore */
 232             goto next;
 233
 234         /* Swap */
 235         tmp = alarm_timers[i];
 236         alarm_timers[i] = alarm_timers[cur];
 237         alarm_timers[cur] = tmp;
 238
 239         cur++;
 240 next:
 241         name = strtok(NULL, ",");
 242     }
 243
 244     g_free(arg);
 245
 246     if (cur) {
 247         /* Disable remaining timers */
 248         for (i = cur; i < count; i++)
 249             alarm_timers[i].name = NULL;
 250     } else {
 251         show_available_alarms();
 252         exit(1);
 253     }
 254 }
 255
 256 QEMUClock *rt_clock;
 257 QEMUClock *vm_clock;
 258 QEMUClock *host_clock;
 259
 260 static QEMUClock *qemu_new_clock(int type)
 261 {
 262     QEMUClock *clock;
 263
 264     clock = g_malloc0(sizeof(QEMUClock));
 265     clock->type = type;
 266     clock->enabled = 1;
 267     clock->last = INT64_MIN;
 268     notifier_list_init(&clock->reset_notifiers);
 269     return clock;
 270 }
 271
 272 void qemu_clock_enable(QEMUClock *clock, int enabled)
 273 {
 274     bool old = clock->enabled;
 275     clock->enabled = enabled;
 276     if (enabled && !old) {
 277         qemu_rearm_alarm_timer(alarm_timer);
 278     }
 279 }
 280
 281 int64_t qemu_clock_has_timers(QEMUClock *clock)
 282 {
 283     return !!clock->active_timers;
 284 }
 285
 286 int64_t qemu_clock_expired(QEMUClock *clock)
 287 {
 288     return (clock->active_timers &&
 289             clock->active_timers->expire_time < qemu_get_clock_ns(clock));
 290 }
 291
 292 int64_t qemu_clock_deadline(QEMUClock *clock)
 293 {
 294     /* To avoid problems with overflow limit this to 2^32.  */
 295     int64_t delta = INT32_MAX;
 296
 297     if (clock->active_timers) {
 298         delta = clock->active_timers->expire_time - qemu_get_clock_ns(clock);
 299     }
 300     if (delta < 0) {
 301         delta = 0;
 302     }
 303     return delta;
 304 }
 305
 306 QEMUTimer *qemu_new_timer(QEMUClock *clock, int scale,
 307                           QEMUTimerCB *cb, void *opaque)
 308 {
 309     QEMUTimer *ts;
 310
 311     ts = g_malloc0(sizeof(QEMUTimer));
 312     ts->clock = clock;
 313     ts->cb = cb;
 314     ts->opaque = opaque;
 315     ts->scale = scale;
 316     return ts;
 317 }
 318
 319 void qemu_free_timer(QEMUTimer *ts)
 320 {
 321     g_free(ts);
 322 }
 323
 324 /* stop a timer, but do not dealloc it */
 325 void qemu_del_timer(QEMUTimer *ts)
 326 {
 327     QEMUTimer **pt, *t;
 328
 329     /* NOTE: this code must be signal safe because
 330        qemu_timer_expired() can be called from a signal. */
 331     pt = &ts->clock->active_timers;
 332     for(;;) {
 333         t = *pt;
 334         if (!t)
 335             break;
 336         if (t == ts) {
 337             *pt = t->next;
 338             break;
 339         }
 340         pt = &t->next;
 341     }
 342 }
 343
 344 /* modify the current timer so that it will be fired when current_time
 345    >= expire_time. The corresponding callback will be called. */
 346 void qemu_mod_timer_ns(QEMUTimer *ts, int64_t expire_time)
 347 {
 348     QEMUTimer **pt, *t;
 349
 350     qemu_del_timer(ts);
 351
 352     /* add the timer in the sorted list */
 353     /* NOTE: this code must be signal safe because
 354        qemu_timer_expired() can be called from a signal. */
 355     pt = &ts->clock->active_timers;
 356     for(;;) {
 357         t = *pt;
 358         if (!qemu_timer_expired_ns(t, expire_time)) {
 359             break;
 360         }
 361         pt = &t->next;
 362     }
 363     ts->expire_time = expire_time;
 364     ts->next = *pt;
 365     *pt = ts;
 366
 367     /* Rearm if necessary  */
 368     if (pt == &ts->clock->active_timers) {
 369         if (!alarm_timer->pending) {
 370             qemu_rearm_alarm_timer(alarm_timer);
 371         }
 372         /* Interrupt execution to force deadline recalculation.  */
 373         qemu_clock_warp(ts->clock);
 374         if (use_icount) {
 375             qemu_notify_event();
 376         }
 377     }
 378 }
 379
 380 void qemu_mod_timer(QEMUTimer *ts, int64_t expire_time)
 381 {
 382     qemu_mod_timer_ns(ts, expire_time * ts->scale);
 383 }
 384
 385 int qemu_timer_pending(QEMUTimer *ts)
 386 {
 387     QEMUTimer *t;
 388     for (t = ts->clock->active_timers; t != NULL; t = t->next) {
 389         if (t == ts)
 390             return 1;
 391     }
 392     return 0;
 393 }
 394
 395 int qemu_timer_expired(QEMUTimer *timer_head, int64_t current_time)
 396 {
 397     return qemu_timer_expired_ns(timer_head, current_time * timer_head->scale);
 398 }
 399
 400 static void qemu_run_timers(QEMUClock *clock)
 401 {
 402     QEMUTimer **ptimer_head, *ts;
 403     int64_t current_time;
 404
 405     if (!clock->enabled)
 406         return;
 407
 408     current_time = qemu_get_clock_ns(clock);
 409     ptimer_head = &clock->active_timers;
 410     for(;;) {
 411         ts = *ptimer_head;
 412         if (!qemu_timer_expired_ns(ts, current_time)) {
 413             break;
 414         }
 415         /* remove timer from the list before calling the callback */
 416         *ptimer_head = ts->next;
 417         ts->next = NULL;
 418
 419         /* run the callback (the timer list can be modified) */
 420         ts->cb(ts->opaque);
 421     }
 422 }
 423
 424 int64_t qemu_get_clock_ns(QEMUClock *clock)
 425 {
 426     int64_t now, last;
 427
 428     switch(clock->type) {
 429     case QEMU_CLOCK_REALTIME:
 430         return get_clock();
 431     default:
 432     case QEMU_CLOCK_VIRTUAL:
 433         if (use_icount) {
 434             return cpu_get_icount();
 435         } else {
 436             return cpu_get_clock();
 437         }
 438     case QEMU_CLOCK_HOST:
 439         now = get_clock_realtime();
 440         last = clock->last;
 441         clock->last = now;
 442         if (now < last) {
 443             notifier_list_notify(&clock->reset_notifiers, &now);
 444         }
 445         return now;
 446     }
 447 }
 448
 449 void qemu_register_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 450 {
 451     notifier_list_add(&clock->reset_notifiers, notifier);
 452 }
 453
 454 void qemu_unregister_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 455 {
 456     notifier_remove(notifier);
 457 }
 458
 459 void init_clocks(void)
 460 {
 461     rt_clock = qemu_new_clock(QEMU_CLOCK_REALTIME);
 462     vm_clock = qemu_new_clock(QEMU_CLOCK_VIRTUAL);
 463     host_clock = qemu_new_clock(QEMU_CLOCK_HOST);
 464 }
 465
 466 uint64_t qemu_timer_expire_time_ns(QEMUTimer *ts)
 467 {
 468     return qemu_timer_pending(ts) ? ts->expire_time : -1;
 469 }
 470
 471 void qemu_run_all_timers(void)
 472 {
 473     alarm_timer->pending = 0;
 474
 475     /* rearm timer, if not periodic */
 476     if (alarm_timer->expired) {
 477         alarm_timer->expired = 0;
 478         qemu_rearm_alarm_timer(alarm_timer);
 479     }
 480
 481     /* vm time timers */
 482     qemu_run_timers(vm_clock);
 483     qemu_run_timers(rt_clock);
 484     qemu_run_timers(host_clock);
 485 }
 486
 487 #ifdef _WIN32
 488 static void CALLBACK host_alarm_handler(PVOID lpParam, BOOLEAN unused)
 489 #else
 490 static void host_alarm_handler(int host_signum)
 491 #endif
 492 {
 493     struct qemu_alarm_timer *t = alarm_timer;
 494     if (!t)
 495         return;
 496
 497     if (alarm_has_dynticks(t) ||
 498         qemu_next_alarm_deadline () <= 0) {
 499         t->expired = alarm_has_dynticks(t);
 500         t->pending = 1;
 501         qemu_notify_event();
 502     }
 503 }
 504
 505 #if defined(__linux__)
 506
 507 #include "compatfd.h"
 508
 509 static int dynticks_start_timer(struct qemu_alarm_timer *t)
 510 {
 511     struct sigevent ev;
 512     timer_t host_timer;
 513     struct sigaction act;
 514
 515     sigfillset(&act.sa_mask);
 516     act.sa_flags = 0;
 517     act.sa_handler = host_alarm_handler;
 518
 519     sigaction(SIGALRM, &act, NULL);
 520
 521     /*
 522      * Initialize ev struct to 0 to avoid valgrind complaining
 523      * about uninitialized data in timer_create call
 524      */
 525     memset(&ev, 0, sizeof(ev));
 526     ev.sigev_value.sival_int = 0;
 527     ev.sigev_notify = SIGEV_SIGNAL;
 528 #ifdef SIGEV_THREAD_ID
 529     if (qemu_signalfd_available()) {
 530         ev.sigev_notify = SIGEV_THREAD_ID;
 531         ev._sigev_un._tid = qemu_get_thread_id();
 532     }
 533 #endif /* SIGEV_THREAD_ID */
 534     ev.sigev_signo = SIGALRM;
 535
 536     if (timer_create(CLOCK_REALTIME, &ev, &host_timer)) {
 537         perror("timer_create");
 538
 539         /* disable dynticks */
 540         fprintf(stderr, "Dynamic Ticks disabled\n");
 541
 542         return -1;
 543     }
 544
 545     t->timer = host_timer;
 546
 547     return 0;
 548 }
 549
 550 static void dynticks_stop_timer(struct qemu_alarm_timer *t)
 551 {
 552     timer_t host_timer = t->timer;
 553
 554     timer_delete(host_timer);
 555 }
 556
 557 static void dynticks_rearm_timer(struct qemu_alarm_timer *t,
 558                                  int64_t nearest_delta_ns)
 559 {
 560     timer_t host_timer = t->timer;
 561     struct itimerspec timeout;
 562     int64_t current_ns;
 563
 564     if (nearest_delta_ns < MIN_TIMER_REARM_NS)
 565         nearest_delta_ns = MIN_TIMER_REARM_NS;
 566
 567     /* check whether a timer is already running */
 568     if (timer_gettime(host_timer, &timeout)) {
 569         perror("gettime");
 570         fprintf(stderr, "Internal timer error: aborting\n");
 571         exit(1);
 572     }
 573     current_ns = timeout.it_value.tv_sec * 1000000000LL + timeout.it_value.tv_nsec;
 574     if (current_ns && current_ns <= nearest_delta_ns)
 575         return;
 576
 577     timeout.it_interval.tv_sec = 0;
 578     timeout.it_interval.tv_nsec = 0; /* 0 for one-shot timer */
 579     timeout.it_value.tv_sec =  nearest_delta_ns / 1000000000;
 580     timeout.it_value.tv_nsec = nearest_delta_ns % 1000000000;
 581     if (timer_settime(host_timer, 0 /* RELATIVE */, &timeout, NULL)) {
 582         perror("settime");
 583         fprintf(stderr, "Internal timer error: aborting\n");
 584         exit(1);
 585     }
 586 }
 587
 588 #endif /* defined(__linux__) */
 589
 590 #if !defined(_WIN32)
 591
 592 static int unix_start_timer(struct qemu_alarm_timer *t)
 593 {
 594     struct sigaction act;
 595
 596     /* timer signal */
 597     sigfillset(&act.sa_mask);
 598     act.sa_flags = 0;
 599     act.sa_handler = host_alarm_handler;
 600
 601     sigaction(SIGALRM, &act, NULL);
 602     return 0;
 603 }
 604
 605 static void unix_rearm_timer(struct qemu_alarm_timer *t,
 606                              int64_t nearest_delta_ns)
 607 {
 608     struct itimerval itv;
 609     int err;
 610
 611     if (nearest_delta_ns < MIN_TIMER_REARM_NS)
 612         nearest_delta_ns = MIN_TIMER_REARM_NS;
 613
 614     itv.it_interval.tv_sec = 0;
 615     itv.it_interval.tv_usec = 0; /* 0 for one-shot timer */
 616     itv.it_value.tv_sec =  nearest_delta_ns / 1000000000;
 617     itv.it_value.tv_usec = (nearest_delta_ns % 1000000000) / 1000;
 618     err = setitimer(ITIMER_REAL, &itv, NULL);
 619     if (err) {
 620         perror("setitimer");
 621         fprintf(stderr, "Internal timer error: aborting\n");
 622         exit(1);
 623     }
 624 }
 625
 626 static void unix_stop_timer(struct qemu_alarm_timer *t)
 627 {
 628     struct itimerval itv;
 629
 630     memset(&itv, 0, sizeof(itv));
 631     setitimer(ITIMER_REAL, &itv, NULL);
 632 }
 633
 634 #endif /* !defined(_WIN32) */
 635
 636
 637 #ifdef _WIN32
 638
 639 static MMRESULT mm_timer;
 640 static unsigned mm_period;
 641
 642 static void CALLBACK mm_alarm_handler(UINT uTimerID, UINT uMsg,
 643                                       DWORD_PTR dwUser, DWORD_PTR dw1,
 644                                       DWORD_PTR dw2)
 645 {
 646     struct qemu_alarm_timer *t = alarm_timer;
 647     if (!t) {
 648         return;
 649     }
 650     if (alarm_has_dynticks(t) || qemu_next_alarm_deadline() <= 0) {
 651         t->expired = alarm_has_dynticks(t);
 652         t->pending = 1;
 653         qemu_notify_event();
 654     }
 655 }
 656
 657 static int mm_start_timer(struct qemu_alarm_timer *t)
 658 {
 659     TIMECAPS tc;
 660     UINT flags;
 661
 662     memset(&tc, 0, sizeof(tc));
 663     timeGetDevCaps(&tc, sizeof(tc));
 664
 665     mm_period = tc.wPeriodMin;
 666     timeBeginPeriod(mm_period);
 667
 668     flags = TIME_CALLBACK_FUNCTION;
 669     if (alarm_has_dynticks(t)) {
 670         flags |= TIME_ONESHOT;
 671     } else {
 672         flags |= TIME_PERIODIC;
 673     }
 674
 675     mm_timer = timeSetEvent(1,                  /* interval (ms) */
 676                             mm_period,          /* resolution */
 677                             mm_alarm_handler,   /* function */
 678                             (DWORD_PTR)t,       /* parameter */
 679                             flags);
 680
 681     if (!mm_timer) {
 682         fprintf(stderr, "Failed to initialize win32 alarm timer: %ld\n",
 683                 GetLastError());
 684         timeEndPeriod(mm_period);
 685         return -1;
 686     }
 687
 688     return 0;
 689 }
 690
 691 static void mm_stop_timer(struct qemu_alarm_timer *t)
 692 {
 693     timeKillEvent(mm_timer);
 694     timeEndPeriod(mm_period);
 695 }
 696
 697 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta)
 698 {
 699     int nearest_delta_ms = (delta + 999999) / 1000000;
 700     if (nearest_delta_ms < 1) {
 701         nearest_delta_ms = 1;
 702     }
 703
 704     timeKillEvent(mm_timer);
 705     mm_timer = timeSetEvent(nearest_delta_ms,
 706                             mm_period,
 707                             mm_alarm_handler,
 708                             (DWORD_PTR)t,
 709                             TIME_ONESHOT | TIME_CALLBACK_FUNCTION);
 710
 711     if (!mm_timer) {
 712         fprintf(stderr, "Failed to re-arm win32 alarm timer %ld\n",
 713                 GetLastError());
 714
 715         timeEndPeriod(mm_period);
 716         exit(1);
 717     }
 718 }
 719
 720 static int win32_start_timer(struct qemu_alarm_timer *t)
 721 {
 722     HANDLE hTimer;
 723     BOOLEAN success;
 724
 725     /* If you call ChangeTimerQueueTimer on a one-shot timer (its period
 726        is zero) that has already expired, the timer is not updated.  Since
 727        creating a new timer is relatively expensive, set a bogus one-hour
 728        interval in the dynticks case.  */
 729     success = CreateTimerQueueTimer(&hTimer,
 730                           NULL,
 731                           host_alarm_handler,
 732                           t,
 733                           1,
 734                           alarm_has_dynticks(t) ? 3600000 : 1,
 735                           WT_EXECUTEINTIMERTHREAD);
 736
 737     if (!success) {
 738         fprintf(stderr, "Failed to initialize win32 alarm timer: %ld\n",
 739                 GetLastError());
 740         return -1;
 741     }
 742
 743     t->timer = hTimer;
 744     return 0;
 745 }
 746
 747 static void win32_stop_timer(struct qemu_alarm_timer *t)
 748 {
 749     HANDLE hTimer = t->timer;
 750
 751     if (hTimer) {
 752         DeleteTimerQueueTimer(NULL, hTimer, NULL);
 753     }
 754 }
 755
 756 static void win32_rearm_timer(struct qemu_alarm_timer *t,
 757                               int64_t nearest_delta_ns)
 758 {
 759     HANDLE hTimer = t->timer;
 760     int nearest_delta_ms;
 761     BOOLEAN success;
 762
 763     nearest_delta_ms = (nearest_delta_ns + 999999) / 1000000;
 764     if (nearest_delta_ms < 1) {
 765         nearest_delta_ms = 1;
 766     }
 767     success = ChangeTimerQueueTimer(NULL,
 768                                     hTimer,
 769                                     nearest_delta_ms,
 770                                     3600000);
 771
 772     if (!success) {
 773         fprintf(stderr, "Failed to rearm win32 alarm timer: %ld\n",
 774                 GetLastError());
 775         exit(-1);
 776     }
 777
 778 }
 779
 780 #endif /* _WIN32 */
 781
 782 static void quit_timers(void)
 783 {
 784     struct qemu_alarm_timer *t = alarm_timer;
 785     alarm_timer = NULL;
 786     t->stop(t);
 787 }
 788
 789 int init_timer_alarm(void)
 790 {
 791     struct qemu_alarm_timer *t = NULL;
 792     int i, err = -1;
 793
 794     for (i = 0; alarm_timers[i].name; i++) {
 795         t = &alarm_timers[i];
 796
 797         err = t->start(t);
 798         if (!err)
 799             break;
 800     }
 801
 802     if (err) {
 803         err = -ENOENT;
 804         goto fail;
 805     }
 806
 807     /* first event is at time 0 */
 808     atexit(quit_timers);
 809     t->pending = 1;
 810     alarm_timer = t;
 811
 812     return 0;
 813
 814 fail:
 815     return err;
 816 }
 817
 818 int qemu_calculate_timeout(void)
 819 {
 820     return 1000;
 821 }
 822