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 = INT64_MAX;
 110     int64_t rtdelta;
 111
 112     if (!use_icount && vm_clock->enabled && vm_clock->active_timers) {
 113         delta = vm_clock->active_timers->expire_time -
 114                      qemu_get_clock_ns(vm_clock);
 115     }
 116     if (host_clock->enabled && host_clock->active_timers) {
 117         int64_t hdelta = host_clock->active_timers->expire_time -
 118                  qemu_get_clock_ns(host_clock);
 119         if (hdelta < delta) {
 120             delta = hdelta;
 121         }
 122     }
 123     if (rt_clock->enabled && rt_clock->active_timers) {
 124         rtdelta = (rt_clock->active_timers->expire_time -
 125                  qemu_get_clock_ns(rt_clock));
 126         if (rtdelta < delta) {
 127             delta = rtdelta;
 128         }
 129     }
 130
 131     return delta;
 132 }
 133
 134 static void qemu_rearm_alarm_timer(struct qemu_alarm_timer *t)
 135 {
 136     int64_t nearest_delta_ns;
 137     assert(alarm_has_dynticks(t));
 138     if (!rt_clock->active_timers &&
 139         !vm_clock->active_timers &&
 140         !host_clock->active_timers) {
 141         return;
 142     }
 143     nearest_delta_ns = qemu_next_alarm_deadline();
 144     t->rearm(t, nearest_delta_ns);
 145 }
 146
 147 /* TODO: MIN_TIMER_REARM_NS should be optimized */
 148 #define MIN_TIMER_REARM_NS 250000
 149
 150 #ifdef _WIN32
 151
 152 static int mm_start_timer(struct qemu_alarm_timer *t);
 153 static void mm_stop_timer(struct qemu_alarm_timer *t);
 154 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 155
 156 static int win32_start_timer(struct qemu_alarm_timer *t);
 157 static void win32_stop_timer(struct qemu_alarm_timer *t);
 158 static void win32_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 159
 160 #else
 161
 162 static int unix_start_timer(struct qemu_alarm_timer *t);
 163 static void unix_stop_timer(struct qemu_alarm_timer *t);
 164 static void unix_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 165
 166 #ifdef __linux__
 167
 168 static int dynticks_start_timer(struct qemu_alarm_timer *t);
 169 static void dynticks_stop_timer(struct qemu_alarm_timer *t);
 170 static void dynticks_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 171
 172 #endif /* __linux__ */
 173
 174 #endif /* _WIN32 */
 175
 176 static struct qemu_alarm_timer alarm_timers[] = {
 177 #ifndef _WIN32
 178 #ifdef __linux__
 179     {"dynticks", dynticks_start_timer,
 180      dynticks_stop_timer, dynticks_rearm_timer},
 181 #endif
 182     {"unix", unix_start_timer, unix_stop_timer, unix_rearm_timer},
 183 #else
 184     {"mmtimer", mm_start_timer, mm_stop_timer, mm_rearm_timer},
 185     {"dynticks", win32_start_timer, win32_stop_timer, win32_rearm_timer},
 186 #endif
 187     {NULL, }
 188 };
 189
 190 static void show_available_alarms(void)
 191 {
 192     int i;
 193
 194     printf("Available alarm timers, in order of precedence:\n");
 195     for (i = 0; alarm_timers[i].name; i++)
 196         printf("%s\n", alarm_timers[i].name);
 197 }
 198
 199 void configure_alarms(char const *opt)
 200 {
 201     int i;
 202     int cur = 0;
 203     int count = ARRAY_SIZE(alarm_timers) - 1;
 204     char *arg;
 205     char *name;
 206     struct qemu_alarm_timer tmp;
 207
 208     if (!strcmp(opt, "?")) {
 209         show_available_alarms();
 210         exit(0);
 211     }
 212
 213     arg = g_strdup(opt);
 214
 215     /* Reorder the array */
 216     name = strtok(arg, ",");
 217     while (name) {
 218         for (i = 0; i < count && alarm_timers[i].name; i++) {
 219             if (!strcmp(alarm_timers[i].name, name))
 220                 break;
 221         }
 222
 223         if (i == count) {
 224             fprintf(stderr, "Unknown clock %s\n", name);
 225             goto next;
 226         }
 227
 228         if (i < cur)
 229             /* Ignore */
 230             goto next;
 231
 232         /* Swap */
 233         tmp = alarm_timers[i];
 234         alarm_timers[i] = alarm_timers[cur];
 235         alarm_timers[cur] = tmp;
 236
 237         cur++;
 238 next:
 239         name = strtok(NULL, ",");
 240     }
 241
 242     g_free(arg);
 243
 244     if (cur) {
 245         /* Disable remaining timers */
 246         for (i = cur; i < count; i++)
 247             alarm_timers[i].name = NULL;
 248     } else {
 249         show_available_alarms();
 250         exit(1);
 251     }
 252 }
 253
 254 QEMUClock *rt_clock;
 255 QEMUClock *vm_clock;
 256 QEMUClock *host_clock;
 257
 258 static QEMUClock *qemu_new_clock(int type)
 259 {
 260     QEMUClock *clock;
 261
 262     clock = g_malloc0(sizeof(QEMUClock));
 263     clock->type = type;
 264     clock->enabled = 1;
 265     clock->last = INT64_MIN;
 266     notifier_list_init(&clock->reset_notifiers);
 267     return clock;
 268 }
 269
 270 void qemu_clock_enable(QEMUClock *clock, int enabled)
 271 {
 272     bool old = clock->enabled;
 273     clock->enabled = enabled;
 274     if (enabled && !old) {
 275         qemu_rearm_alarm_timer(alarm_timer);
 276     }
 277 }
 278
 279 int64_t qemu_clock_has_timers(QEMUClock *clock)
 280 {
 281     return !!clock->active_timers;
 282 }
 283
 284 int64_t qemu_clock_expired(QEMUClock *clock)
 285 {
 286     return (clock->active_timers &&
 287             clock->active_timers->expire_time < qemu_get_clock_ns(clock));
 288 }
 289
 290 int64_t qemu_clock_deadline(QEMUClock *clock)
 291 {
 292     /* To avoid problems with overflow limit this to 2^32.  */
 293     int64_t delta = INT32_MAX;
 294
 295     if (clock->active_timers) {
 296         delta = clock->active_timers->expire_time - qemu_get_clock_ns(clock);
 297     }
 298     if (delta < 0) {
 299         delta = 0;
 300     }
 301     return delta;
 302 }
 303
 304 QEMUTimer *qemu_new_timer(QEMUClock *clock, int scale,
 305                           QEMUTimerCB *cb, void *opaque)
 306 {
 307     QEMUTimer *ts;
 308
 309     ts = g_malloc0(sizeof(QEMUTimer));
 310     ts->clock = clock;
 311     ts->cb = cb;
 312     ts->opaque = opaque;
 313     ts->scale = scale;
 314     return ts;
 315 }
 316
 317 void qemu_free_timer(QEMUTimer *ts)
 318 {
 319     g_free(ts);
 320 }
 321
 322 /* stop a timer, but do not dealloc it */
 323 void qemu_del_timer(QEMUTimer *ts)
 324 {
 325     QEMUTimer **pt, *t;
 326
 327     /* NOTE: this code must be signal safe because
 328        qemu_timer_expired() can be called from a signal. */
 329     pt = &ts->clock->active_timers;
 330     for(;;) {
 331         t = *pt;
 332         if (!t)
 333             break;
 334         if (t == ts) {
 335             *pt = t->next;
 336             break;
 337         }
 338         pt = &t->next;
 339     }
 340 }
 341
 342 /* modify the current timer so that it will be fired when current_time
 343    >= expire_time. The corresponding callback will be called. */
 344 void qemu_mod_timer_ns(QEMUTimer *ts, int64_t expire_time)
 345 {
 346     QEMUTimer **pt, *t;
 347
 348     qemu_del_timer(ts);
 349
 350     /* add the timer in the sorted list */
 351     /* NOTE: this code must be signal safe because
 352        qemu_timer_expired() can be called from a signal. */
 353     pt = &ts->clock->active_timers;
 354     for(;;) {
 355         t = *pt;
 356         if (!qemu_timer_expired_ns(t, expire_time)) {
 357             break;
 358         }
 359         pt = &t->next;
 360     }
 361     ts->expire_time = expire_time;
 362     ts->next = *pt;
 363     *pt = ts;
 364
 365     /* Rearm if necessary  */
 366     if (pt == &ts->clock->active_timers) {
 367         if (!alarm_timer->pending) {
 368             qemu_rearm_alarm_timer(alarm_timer);
 369         }
 370         /* Interrupt execution to force deadline recalculation.  */
 371         qemu_clock_warp(ts->clock);
 372         if (use_icount) {
 373             qemu_notify_event();
 374         }
 375     }
 376 }
 377
 378 void qemu_mod_timer(QEMUTimer *ts, int64_t expire_time)
 379 {
 380     qemu_mod_timer_ns(ts, expire_time * ts->scale);
 381 }
 382
 383 int qemu_timer_pending(QEMUTimer *ts)
 384 {
 385     QEMUTimer *t;
 386     for (t = ts->clock->active_timers; t != NULL; t = t->next) {
 387         if (t == ts)
 388             return 1;
 389     }
 390     return 0;
 391 }
 392
 393 int qemu_timer_expired(QEMUTimer *timer_head, int64_t current_time)
 394 {
 395     return qemu_timer_expired_ns(timer_head, current_time * timer_head->scale);
 396 }
 397
 398 void qemu_run_timers(QEMUClock *clock)
 399 {
 400     QEMUTimer **ptimer_head, *ts;
 401     int64_t current_time;
 402
 403     if (!clock->enabled)
 404         return;
 405
 406     current_time = qemu_get_clock_ns(clock);
 407     ptimer_head = &clock->active_timers;
 408     for(;;) {
 409         ts = *ptimer_head;
 410         if (!qemu_timer_expired_ns(ts, current_time)) {
 411             break;
 412         }
 413         /* remove timer from the list before calling the callback */
 414         *ptimer_head = ts->next;
 415         ts->next = NULL;
 416
 417         /* run the callback (the timer list can be modified) */
 418         ts->cb(ts->opaque);
 419     }
 420 }
 421
 422 int64_t qemu_get_clock_ns(QEMUClock *clock)
 423 {
 424     int64_t now, last;
 425
 426     switch(clock->type) {
 427     case QEMU_CLOCK_REALTIME:
 428         return get_clock();
 429     default:
 430     case QEMU_CLOCK_VIRTUAL:
 431         if (use_icount) {
 432             return cpu_get_icount();
 433         } else {
 434             return cpu_get_clock();
 435         }
 436     case QEMU_CLOCK_HOST:
 437         now = get_clock_realtime();
 438         last = clock->last;
 439         clock->last = now;
 440         if (now < last) {
 441             notifier_list_notify(&clock->reset_notifiers, &now);
 442         }
 443         return now;
 444     }
 445 }
 446
 447 void qemu_register_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 448 {
 449     notifier_list_add(&clock->reset_notifiers, notifier);
 450 }
 451
 452 void qemu_unregister_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 453 {
 454     notifier_remove(notifier);
 455 }
 456
 457 void init_clocks(void)
 458 {
 459     rt_clock = qemu_new_clock(QEMU_CLOCK_REALTIME);
 460     vm_clock = qemu_new_clock(QEMU_CLOCK_VIRTUAL);
 461     host_clock = qemu_new_clock(QEMU_CLOCK_HOST);
 462 }
 463
 464 uint64_t qemu_timer_expire_time_ns(QEMUTimer *ts)
 465 {
 466     return qemu_timer_pending(ts) ? ts->expire_time : -1;
 467 }
 468
 469 void qemu_run_all_timers(void)
 470 {
 471     alarm_timer->pending = 0;
 472
 473     /* vm time timers */
 474     qemu_run_timers(vm_clock);
 475     qemu_run_timers(rt_clock);
 476     qemu_run_timers(host_clock);
 477
 478     /* rearm timer, if not periodic */
 479     if (alarm_timer->expired) {
 480         alarm_timer->expired = 0;
 481         qemu_rearm_alarm_timer(alarm_timer);
 482     }
 483 }
 484
 485 #ifdef _WIN32
 486 static void CALLBACK host_alarm_handler(PVOID lpParam, BOOLEAN unused)
 487 #else
 488 static void host_alarm_handler(int host_signum)
 489 #endif
 490 {
 491     struct qemu_alarm_timer *t = alarm_timer;
 492     if (!t)
 493         return;
 494
 495     if (alarm_has_dynticks(t) ||
 496         qemu_next_alarm_deadline () <= 0) {
 497         t->expired = alarm_has_dynticks(t);
 498         t->pending = 1;
 499         qemu_notify_event();
 500     }
 501 }
 502
 503 #if defined(__linux__)
 504
 505 #include "compatfd.h"
 506
 507 static int dynticks_start_timer(struct qemu_alarm_timer *t)
 508 {
 509     struct sigevent ev;
 510     timer_t host_timer;
 511     struct sigaction act;
 512
 513     sigfillset(&act.sa_mask);
 514     act.sa_flags = 0;
 515     act.sa_handler = host_alarm_handler;
 516
 517     sigaction(SIGALRM, &act, NULL);
 518
 519     /*
 520      * Initialize ev struct to 0 to avoid valgrind complaining
 521      * about uninitialized data in timer_create call
 522      */
 523     memset(&ev, 0, sizeof(ev));
 524     ev.sigev_value.sival_int = 0;
 525     ev.sigev_notify = SIGEV_SIGNAL;
 526 #ifdef SIGEV_THREAD_ID
 527     if (qemu_signalfd_available()) {
 528         ev.sigev_notify = SIGEV_THREAD_ID;
 529         ev._sigev_un._tid = qemu_get_thread_id();
 530     }
 531 #endif /* SIGEV_THREAD_ID */
 532     ev.sigev_signo = SIGALRM;
 533
 534     if (timer_create(CLOCK_REALTIME, &ev, &host_timer)) {
 535         perror("timer_create");
 536
 537         /* disable dynticks */
 538         fprintf(stderr, "Dynamic Ticks disabled\n");
 539
 540         return -1;
 541     }
 542
 543     t->timer = host_timer;
 544
 545     return 0;
 546 }
 547
 548 static void dynticks_stop_timer(struct qemu_alarm_timer *t)
 549 {
 550     timer_t host_timer = t->timer;
 551
 552     timer_delete(host_timer);
 553 }
 554
 555 static void dynticks_rearm_timer(struct qemu_alarm_timer *t,
 556                                  int64_t nearest_delta_ns)
 557 {
 558     timer_t host_timer = t->timer;
 559     struct itimerspec timeout;
 560     int64_t current_ns;
 561
 562     if (nearest_delta_ns < MIN_TIMER_REARM_NS)
 563         nearest_delta_ns = MIN_TIMER_REARM_NS;
 564
 565     /* check whether a timer is already running */
 566     if (timer_gettime(host_timer, &timeout)) {
 567         perror("gettime");
 568         fprintf(stderr, "Internal timer error: aborting\n");
 569         exit(1);
 570     }
 571     current_ns = timeout.it_value.tv_sec * 1000000000LL + timeout.it_value.tv_nsec;
 572     if (current_ns && current_ns <= nearest_delta_ns)
 573         return;
 574
 575     timeout.it_interval.tv_sec = 0;
 576     timeout.it_interval.tv_nsec = 0; /* 0 for one-shot timer */
 577     timeout.it_value.tv_sec =  nearest_delta_ns / 1000000000;
 578     timeout.it_value.tv_nsec = nearest_delta_ns % 1000000000;
 579     if (timer_settime(host_timer, 0 /* RELATIVE */, &timeout, NULL)) {
 580         perror("settime");
 581         fprintf(stderr, "Internal timer error: aborting\n");
 582         exit(1);
 583     }
 584 }
 585
 586 #endif /* defined(__linux__) */
 587
 588 #if !defined(_WIN32)
 589
 590 static int unix_start_timer(struct qemu_alarm_timer *t)
 591 {
 592     struct sigaction act;
 593
 594     /* timer signal */
 595     sigfillset(&act.sa_mask);
 596     act.sa_flags = 0;
 597     act.sa_handler = host_alarm_handler;
 598
 599     sigaction(SIGALRM, &act, NULL);
 600     return 0;
 601 }
 602
 603 static void unix_rearm_timer(struct qemu_alarm_timer *t,
 604                              int64_t nearest_delta_ns)
 605 {
 606     struct itimerval itv;
 607     int err;
 608
 609     if (nearest_delta_ns < MIN_TIMER_REARM_NS)
 610         nearest_delta_ns = MIN_TIMER_REARM_NS;
 611
 612     itv.it_interval.tv_sec = 0;
 613     itv.it_interval.tv_usec = 0; /* 0 for one-shot timer */
 614     itv.it_value.tv_sec =  nearest_delta_ns / 1000000000;
 615     itv.it_value.tv_usec = (nearest_delta_ns % 1000000000) / 1000;
 616     err = setitimer(ITIMER_REAL, &itv, NULL);
 617     if (err) {
 618         perror("setitimer");
 619         fprintf(stderr, "Internal timer error: aborting\n");
 620         exit(1);
 621     }
 622 }
 623
 624 static void unix_stop_timer(struct qemu_alarm_timer *t)
 625 {
 626     struct itimerval itv;
 627
 628     memset(&itv, 0, sizeof(itv));
 629     setitimer(ITIMER_REAL, &itv, NULL);
 630 }
 631
 632 #endif /* !defined(_WIN32) */
 633
 634
 635 #ifdef _WIN32
 636
 637 static MMRESULT mm_timer;
 638 static unsigned mm_period;
 639
 640 static void CALLBACK mm_alarm_handler(UINT uTimerID, UINT uMsg,
 641                                       DWORD_PTR dwUser, DWORD_PTR dw1,
 642                                       DWORD_PTR dw2)
 643 {
 644     struct qemu_alarm_timer *t = alarm_timer;
 645     if (!t) {
 646         return;
 647     }
 648     if (alarm_has_dynticks(t) || qemu_next_alarm_deadline() <= 0) {
 649         t->expired = alarm_has_dynticks(t);
 650         t->pending = 1;
 651         qemu_notify_event();
 652     }
 653 }
 654
 655 static int mm_start_timer(struct qemu_alarm_timer *t)
 656 {
 657     TIMECAPS tc;
 658     UINT flags;
 659
 660     memset(&tc, 0, sizeof(tc));
 661     timeGetDevCaps(&tc, sizeof(tc));
 662
 663     mm_period = tc.wPeriodMin;
 664     timeBeginPeriod(mm_period);
 665
 666     flags = TIME_CALLBACK_FUNCTION;
 667     if (alarm_has_dynticks(t)) {
 668         flags |= TIME_ONESHOT;
 669     } else {
 670         flags |= TIME_PERIODIC;
 671     }
 672
 673     mm_timer = timeSetEvent(1,                  /* interval (ms) */
 674                             mm_period,          /* resolution */
 675                             mm_alarm_handler,   /* function */
 676                             (DWORD_PTR)t,       /* parameter */
 677                             flags);
 678
 679     if (!mm_timer) {
 680         fprintf(stderr, "Failed to initialize win32 alarm timer: %ld\n",
 681                 GetLastError());
 682         timeEndPeriod(mm_period);
 683         return -1;
 684     }
 685
 686     return 0;
 687 }
 688
 689 static void mm_stop_timer(struct qemu_alarm_timer *t)
 690 {
 691     timeKillEvent(mm_timer);
 692     timeEndPeriod(mm_period);
 693 }
 694
 695 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta)
 696 {
 697     int64_t nearest_delta_ms = delta / 1000000;
 698     if (nearest_delta_ms < 1) {
 699         nearest_delta_ms = 1;
 700     }
 701     /* UINT_MAX can be 32 bit */
 702     if (nearest_delta_ms > UINT_MAX) {
 703         nearest_delta_ms = UINT_MAX;
 704     }
 705
 706     timeKillEvent(mm_timer);
 707     mm_timer = timeSetEvent((unsigned int) nearest_delta_ms,
 708                             mm_period,
 709                             mm_alarm_handler,
 710                             (DWORD_PTR)t,
 711                             TIME_ONESHOT | TIME_CALLBACK_FUNCTION);
 712
 713     if (!mm_timer) {
 714         fprintf(stderr, "Failed to re-arm win32 alarm timer %ld\n",
 715                 GetLastError());
 716
 717         timeEndPeriod(mm_period);
 718         exit(1);
 719     }
 720 }
 721
 722 static int win32_start_timer(struct qemu_alarm_timer *t)
 723 {
 724     HANDLE hTimer;
 725     BOOLEAN success;
 726
 727     /* If you call ChangeTimerQueueTimer on a one-shot timer (its period
 728        is zero) that has already expired, the timer is not updated.  Since
 729        creating a new timer is relatively expensive, set a bogus one-hour
 730        interval in the dynticks case.  */
 731     success = CreateTimerQueueTimer(&hTimer,
 732                           NULL,
 733                           host_alarm_handler,
 734                           t,
 735                           1,
 736                           alarm_has_dynticks(t) ? 3600000 : 1,
 737                           WT_EXECUTEINTIMERTHREAD);
 738
 739     if (!success) {
 740         fprintf(stderr, "Failed to initialize win32 alarm timer: %ld\n",
 741                 GetLastError());
 742         return -1;
 743     }
 744
 745     t->timer = hTimer;
 746     return 0;
 747 }
 748
 749 static void win32_stop_timer(struct qemu_alarm_timer *t)
 750 {
 751     HANDLE hTimer = t->timer;
 752
 753     if (hTimer) {
 754         DeleteTimerQueueTimer(NULL, hTimer, NULL);
 755     }
 756 }
 757
 758 static void win32_rearm_timer(struct qemu_alarm_timer *t,
 759                               int64_t nearest_delta_ns)
 760 {
 761     HANDLE hTimer = t->timer;
 762     int64_t nearest_delta_ms;
 763     BOOLEAN success;
 764
 765     nearest_delta_ms = nearest_delta_ns / 1000000;
 766     if (nearest_delta_ms < 1) {
 767         nearest_delta_ms = 1;
 768     }
 769     /* ULONG_MAX can be 32 bit */
 770     if (nearest_delta_ms > ULONG_MAX) {
 771         nearest_delta_ms = ULONG_MAX;
 772     }
 773     success = ChangeTimerQueueTimer(NULL,
 774                                     hTimer,
 775                                     (unsigned long) nearest_delta_ms,
 776                                     3600000);
 777
 778     if (!success) {
 779         fprintf(stderr, "Failed to rearm win32 alarm timer: %ld\n",
 780                 GetLastError());
 781         exit(-1);
 782     }
 783
 784 }
 785
 786 #endif /* _WIN32 */
 787
 788 static void quit_timers(void)
 789 {
 790     struct qemu_alarm_timer *t = alarm_timer;
 791     alarm_timer = NULL;
 792     t->stop(t);
 793 }
 794
 795 int init_timer_alarm(void)
 796 {
 797     struct qemu_alarm_timer *t = NULL;
 798     int i, err = -1;
 799
 800     for (i = 0; alarm_timers[i].name; i++) {
 801         t = &alarm_timers[i];
 802
 803         err = t->start(t);
 804         if (!err)
 805             break;
 806     }
 807
 808     if (err) {
 809         err = -ENOENT;
 810         goto fail;
 811     }
 812
 813     /* first event is at time 0 */
 814     atexit(quit_timers);
 815     t->pending = 1;
 816     alarm_timer = t;
 817
 818     return 0;
 819
 820 fail:
 821     return err;
 822 }
 823