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