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 #ifdef CONFIG_PPOLL
  41 #include <poll.h>
  42 #endif
  43
  44 #ifdef CONFIG_PRCTL_PR_SET_TIMERSLACK
  45 #include <sys/prctl.h>
  46 #endif
  47
  48 /***********************************************************/
  49 /* timers */
  50
  51 struct QEMUClock {
  52     QEMUTimerList *main_loop_timerlist;
  53     QLIST_HEAD(, QEMUTimerList) timerlists;
  54
  55     NotifierList reset_notifiers;
  56     int64_t last;
  57
  58     QEMUClockType type;
  59     bool enabled;
  60 };
  61
  62 QEMUTimerListGroup main_loop_tlg;
  63 QEMUClock *qemu_clocks[QEMU_CLOCK_MAX];
  64
  65 /* A QEMUTimerList is a list of timers attached to a clock. More
  66  * than one QEMUTimerList can be attached to each clock, for instance
  67  * used by different AioContexts / threads. Each clock also has
  68  * a list of the QEMUTimerLists associated with it, in order that
  69  * reenabling the clock can call all the notifiers.
  70  */
  71
  72 struct QEMUTimerList {
  73     QEMUClock *clock;
  74     QEMUTimer *active_timers;
  75     QLIST_ENTRY(QEMUTimerList) list;
  76     QEMUTimerListNotifyCB *notify_cb;
  77     void *notify_opaque;
  78 };
  79
  80 struct qemu_alarm_timer {
  81     char const *name;
  82     int (*start)(struct qemu_alarm_timer *t);
  83     void (*stop)(struct qemu_alarm_timer *t);
  84     void (*rearm)(struct qemu_alarm_timer *t, int64_t nearest_delta_ns);
  85 #if defined(__linux__)
  86     timer_t timer;
  87     int fd;
  88 #elif defined(_WIN32)
  89     HANDLE timer;
  90 #endif
  91     bool expired;
  92     bool pending;
  93 };
  94
  95 static struct qemu_alarm_timer *alarm_timer;
  96
  97 static bool timer_expired_ns(QEMUTimer *timer_head, int64_t current_time)
  98 {
  99     return timer_head && (timer_head->expire_time <= current_time);
 100 }
 101
 102 static int64_t qemu_next_alarm_deadline(void)
 103 {
 104     int64_t delta = INT64_MAX;
 105     int64_t rtdelta;
 106     int64_t hdelta;
 107
 108     if (!use_icount && vm_clock->enabled &&
 109         vm_clock->main_loop_timerlist->active_timers) {
 110         delta = vm_clock->main_loop_timerlist->active_timers->expire_time -
 111             qemu_get_clock_ns(vm_clock);
 112     }
 113     if (host_clock->enabled &&
 114         host_clock->main_loop_timerlist->active_timers) {
 115         hdelta = host_clock->main_loop_timerlist->active_timers->expire_time -
 116             qemu_get_clock_ns(host_clock);
 117         if (hdelta < delta) {
 118             delta = hdelta;
 119         }
 120     }
 121     if (rt_clock->enabled &&
 122         rt_clock->main_loop_timerlist->active_timers) {
 123         rtdelta = (rt_clock->main_loop_timerlist->active_timers->expire_time -
 124                    qemu_get_clock_ns(rt_clock));
 125         if (rtdelta < delta) {
 126             delta = rtdelta;
 127         }
 128     }
 129
 130     return delta;
 131 }
 132
 133 static void qemu_rearm_alarm_timer(struct qemu_alarm_timer *t)
 134 {
 135     int64_t nearest_delta_ns = qemu_next_alarm_deadline();
 136     if (nearest_delta_ns < INT64_MAX) {
 137         t->rearm(t, nearest_delta_ns);
 138     }
 139 }
 140
 141 /* TODO: MIN_TIMER_REARM_NS should be optimized */
 142 #define MIN_TIMER_REARM_NS 250000
 143
 144 #ifdef _WIN32
 145
 146 static int mm_start_timer(struct qemu_alarm_timer *t);
 147 static void mm_stop_timer(struct qemu_alarm_timer *t);
 148 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 149
 150 static int win32_start_timer(struct qemu_alarm_timer *t);
 151 static void win32_stop_timer(struct qemu_alarm_timer *t);
 152 static void win32_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 153
 154 #else
 155
 156 static int unix_start_timer(struct qemu_alarm_timer *t);
 157 static void unix_stop_timer(struct qemu_alarm_timer *t);
 158 static void unix_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 159
 160 #ifdef __linux__
 161
 162 static int dynticks_start_timer(struct qemu_alarm_timer *t);
 163 static void dynticks_stop_timer(struct qemu_alarm_timer *t);
 164 static void dynticks_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 165
 166 #endif /* __linux__ */
 167
 168 #endif /* _WIN32 */
 169
 170 static struct qemu_alarm_timer alarm_timers[] = {
 171 #ifndef _WIN32
 172 #ifdef __linux__
 173     {"dynticks", dynticks_start_timer,
 174      dynticks_stop_timer, dynticks_rearm_timer},
 175 #endif
 176     {"unix", unix_start_timer, unix_stop_timer, unix_rearm_timer},
 177 #else
 178     {"mmtimer", mm_start_timer, mm_stop_timer, mm_rearm_timer},
 179     {"dynticks", win32_start_timer, win32_stop_timer, win32_rearm_timer},
 180 #endif
 181     {NULL, }
 182 };
 183
 184 static void show_available_alarms(void)
 185 {
 186     int i;
 187
 188     printf("Available alarm timers, in order of precedence:\n");
 189     for (i = 0; alarm_timers[i].name; i++)
 190         printf("%s\n", alarm_timers[i].name);
 191 }
 192
 193 void configure_alarms(char const *opt)
 194 {
 195     int i;
 196     int cur = 0;
 197     int count = ARRAY_SIZE(alarm_timers) - 1;
 198     char *arg;
 199     char *name;
 200     struct qemu_alarm_timer tmp;
 201
 202     if (is_help_option(opt)) {
 203         show_available_alarms();
 204         exit(0);
 205     }
 206
 207     arg = g_strdup(opt);
 208
 209     /* Reorder the array */
 210     name = strtok(arg, ",");
 211     while (name) {
 212         for (i = 0; i < count && alarm_timers[i].name; i++) {
 213             if (!strcmp(alarm_timers[i].name, name))
 214                 break;
 215         }
 216
 217         if (i == count) {
 218             fprintf(stderr, "Unknown clock %s\n", name);
 219             goto next;
 220         }
 221
 222         if (i < cur)
 223             /* Ignore */
 224             goto next;
 225
 226         /* Swap */
 227         tmp = alarm_timers[i];
 228         alarm_timers[i] = alarm_timers[cur];
 229         alarm_timers[cur] = tmp;
 230
 231         cur++;
 232 next:
 233         name = strtok(NULL, ",");
 234     }
 235
 236     g_free(arg);
 237
 238     if (cur) {
 239         /* Disable remaining timers */
 240         for (i = cur; i < count; i++)
 241             alarm_timers[i].name = NULL;
 242     } else {
 243         show_available_alarms();
 244         exit(1);
 245     }
 246 }
 247
 248 static QEMUTimerList *timerlist_new_from_clock(QEMUClock *clock,
 249                                                QEMUTimerListNotifyCB *cb,
 250                                                void *opaque)
 251 {
 252     QEMUTimerList *timer_list;
 253
 254     /* Assert if we do not have a clock. If you see this
 255      * assertion in means that the clocks have not been
 256      * initialised before a timerlist is needed. This
 257      * normally happens if an AioContext is used before
 258      * init_clocks() is called within main().
 259      */
 260     assert(clock);
 261
 262     timer_list = g_malloc0(sizeof(QEMUTimerList));
 263     timer_list->clock = clock;
 264     timer_list->notify_cb = cb;
 265     timer_list->notify_opaque = opaque;
 266     QLIST_INSERT_HEAD(&clock->timerlists, timer_list, list);
 267     return timer_list;
 268 }
 269
 270 QEMUTimerList *timerlist_new(QEMUClockType type,
 271                              QEMUTimerListNotifyCB *cb, void *opaque)
 272 {
 273     return timerlist_new_from_clock(qemu_clock_ptr(type), cb, opaque);
 274 }
 275
 276 void timerlist_free(QEMUTimerList *timer_list)
 277 {
 278     assert(!timerlist_has_timers(timer_list));
 279     if (timer_list->clock) {
 280         QLIST_REMOVE(timer_list, list);
 281         if (timer_list->clock->main_loop_timerlist == timer_list) {
 282             timer_list->clock->main_loop_timerlist = NULL;
 283         }
 284     }
 285     g_free(timer_list);
 286 }
 287
 288 static QEMUClock *qemu_clock_new(QEMUClockType type)
 289 {
 290     QEMUClock *clock;
 291
 292     clock = g_malloc0(sizeof(QEMUClock));
 293     clock->type = type;
 294     clock->enabled = true;
 295     clock->last = INT64_MIN;
 296     QLIST_INIT(&clock->timerlists);
 297     notifier_list_init(&clock->reset_notifiers);
 298     clock->main_loop_timerlist = timerlist_new_from_clock(clock, NULL, NULL);
 299     return clock;
 300 }
 301
 302 bool qemu_clock_use_for_deadline(QEMUClock *clock)
 303 {
 304     return !(use_icount && (clock->type == QEMU_CLOCK_VIRTUAL));
 305 }
 306
 307 void qemu_clock_notify(QEMUClock *clock)
 308 {
 309     QEMUTimerList *timer_list;
 310     QLIST_FOREACH(timer_list, &clock->timerlists, list) {
 311         timerlist_notify(timer_list);
 312     }
 313 }
 314
 315 void qemu_clock_enable(QEMUClock *clock, bool enabled)
 316 {
 317     bool old = clock->enabled;
 318     clock->enabled = enabled;
 319     if (enabled && !old) {
 320         qemu_clock_notify(clock);
 321         qemu_rearm_alarm_timer(alarm_timer);
 322     }
 323 }
 324
 325 bool timerlist_has_timers(QEMUTimerList *timer_list)
 326 {
 327     return !!timer_list->active_timers;
 328 }
 329
 330 bool qemu_clock_has_timers(QEMUClock *clock)
 331 {
 332     return timerlist_has_timers(clock->main_loop_timerlist);
 333 }
 334
 335 bool timerlist_expired(QEMUTimerList *timer_list)
 336 {
 337     return (timer_list->active_timers &&
 338             timer_list->active_timers->expire_time <
 339             qemu_get_clock_ns(timer_list->clock));
 340 }
 341
 342 bool qemu_clock_expired(QEMUClock *clock)
 343 {
 344     return timerlist_expired(clock->main_loop_timerlist);
 345 }
 346
 347 int64_t timerlist_deadline(QEMUTimerList *timer_list)
 348 {
 349     /* To avoid problems with overflow limit this to 2^32.  */
 350     int64_t delta = INT32_MAX;
 351
 352     if (timer_list->clock->enabled && timer_list->active_timers) {
 353         delta = timer_list->active_timers->expire_time -
 354             qemu_get_clock_ns(timer_list->clock);
 355     }
 356     if (delta < 0) {
 357         delta = 0;
 358     }
 359     return delta;
 360 }
 361
 362 int64_t qemu_clock_deadline(QEMUClock *clock)
 363 {
 364     return timerlist_deadline(clock->main_loop_timerlist);
 365 }
 366
 367 /*
 368  * As above, but return -1 for no deadline, and do not cap to 2^32
 369  * as we know the result is always positive.
 370  */
 371
 372 int64_t timerlist_deadline_ns(QEMUTimerList *timer_list)
 373 {
 374     int64_t delta;
 375
 376     if (!timer_list->clock->enabled || !timer_list->active_timers) {
 377         return -1;
 378     }
 379
 380     delta = timer_list->active_timers->expire_time -
 381         qemu_get_clock_ns(timer_list->clock);
 382
 383     if (delta <= 0) {
 384         return 0;
 385     }
 386
 387     return delta;
 388 }
 389
 390 int64_t qemu_clock_deadline_ns(QEMUClock *clock)
 391 {
 392     return timerlist_deadline_ns(clock->main_loop_timerlist);
 393 }
 394
 395 QEMUClock *timerlist_get_clock(QEMUTimerList *timer_list)
 396 {
 397     return timer_list->clock;
 398 }
 399
 400 QEMUTimerList *qemu_clock_get_main_loop_timerlist(QEMUClock *clock)
 401 {
 402     return clock->main_loop_timerlist;
 403 }
 404
 405 void timerlist_notify(QEMUTimerList *timer_list)
 406 {
 407     if (timer_list->notify_cb) {
 408         timer_list->notify_cb(timer_list->notify_opaque);
 409     } else {
 410         qemu_notify_event();
 411     }
 412 }
 413
 414 /* Transition function to convert a nanosecond timeout to ms
 415  * This is used where a system does not support ppoll
 416  */
 417 int qemu_timeout_ns_to_ms(int64_t ns)
 418 {
 419     int64_t ms;
 420     if (ns < 0) {
 421         return -1;
 422     }
 423
 424     if (!ns) {
 425         return 0;
 426     }
 427
 428     /* Always round up, because it's better to wait too long than to wait too
 429      * little and effectively busy-wait
 430      */
 431     ms = (ns + SCALE_MS - 1) / SCALE_MS;
 432
 433     /* To avoid overflow problems, limit this to 2^31, i.e. approx 25 days */
 434     if (ms > (int64_t) INT32_MAX) {
 435         ms = INT32_MAX;
 436     }
 437
 438     return (int) ms;
 439 }
 440
 441
 442 /* qemu implementation of g_poll which uses a nanosecond timeout but is
 443  * otherwise identical to g_poll
 444  */
 445 int qemu_poll_ns(GPollFD *fds, guint nfds, int64_t timeout)
 446 {
 447 #ifdef CONFIG_PPOLL
 448     if (timeout < 0) {
 449         return ppoll((struct pollfd *)fds, nfds, NULL, NULL);
 450     } else {
 451         struct timespec ts;
 452         ts.tv_sec = timeout / 1000000000LL;
 453         ts.tv_nsec = timeout % 1000000000LL;
 454         return ppoll((struct pollfd *)fds, nfds, &ts, NULL);
 455     }
 456 #else
 457     return g_poll(fds, nfds, qemu_timeout_ns_to_ms(timeout));
 458 #endif
 459 }
 460
 461
 462 void timer_init(QEMUTimer *ts,
 463                 QEMUTimerList *timer_list, int scale,
 464                 QEMUTimerCB *cb, void *opaque)
 465 {
 466     ts->timer_list = timer_list;
 467     ts->cb = cb;
 468     ts->opaque = opaque;
 469     ts->scale = scale;
 470 }
 471
 472 QEMUTimer *qemu_new_timer(QEMUClock *clock, int scale,
 473                           QEMUTimerCB *cb, void *opaque)
 474 {
 475     return timer_new_tl(clock->main_loop_timerlist,
 476                      scale, cb, opaque);
 477 }
 478
 479 void qemu_free_timer(QEMUTimer *ts)
 480 {
 481     g_free(ts);
 482 }
 483
 484 /* stop a timer, but do not dealloc it */
 485 void qemu_del_timer(QEMUTimer *ts)
 486 {
 487     QEMUTimer **pt, *t;
 488
 489     /* NOTE: this code must be signal safe because
 490        timer_expired() can be called from a signal. */
 491     pt = &ts->timer_list->active_timers;
 492     for(;;) {
 493         t = *pt;
 494         if (!t)
 495             break;
 496         if (t == ts) {
 497             *pt = t->next;
 498             break;
 499         }
 500         pt = &t->next;
 501     }
 502 }
 503
 504 /* modify the current timer so that it will be fired when current_time
 505    >= expire_time. The corresponding callback will be called. */
 506 void qemu_mod_timer_ns(QEMUTimer *ts, int64_t expire_time)
 507 {
 508     QEMUTimer **pt, *t;
 509
 510     qemu_del_timer(ts);
 511
 512     /* add the timer in the sorted list */
 513     /* NOTE: this code must be signal safe because
 514        timer_expired() can be called from a signal. */
 515     pt = &ts->timer_list->active_timers;
 516     for(;;) {
 517         t = *pt;
 518         if (!timer_expired_ns(t, expire_time)) {
 519             break;
 520         }
 521         pt = &t->next;
 522     }
 523     ts->expire_time = expire_time;
 524     ts->next = *pt;
 525     *pt = ts;
 526
 527     /* Rearm if necessary  */
 528     if (pt == &ts->timer_list->active_timers) {
 529         if (!alarm_timer->pending) {
 530             qemu_rearm_alarm_timer(alarm_timer);
 531         }
 532         /* Interrupt execution to force deadline recalculation.  */
 533         qemu_clock_warp(ts->timer_list->clock);
 534         timerlist_notify(ts->timer_list);
 535     }
 536 }
 537
 538 void qemu_mod_timer(QEMUTimer *ts, int64_t expire_time)
 539 {
 540     qemu_mod_timer_ns(ts, expire_time * ts->scale);
 541 }
 542
 543 bool timer_pending(QEMUTimer *ts)
 544 {
 545     QEMUTimer *t;
 546     for (t = ts->timer_list->active_timers; t != NULL; t = t->next) {
 547         if (t == ts) {
 548             return true;
 549         }
 550     }
 551     return false;
 552 }
 553
 554 bool timer_expired(QEMUTimer *timer_head, int64_t current_time)
 555 {
 556     return timer_expired_ns(timer_head, current_time * timer_head->scale);
 557 }
 558
 559 bool timerlist_run_timers(QEMUTimerList *timer_list)
 560 {
 561     QEMUTimer *ts;
 562     int64_t current_time;
 563     bool progress = false;
 564
 565     if (!timer_list->clock->enabled) {
 566         return progress;
 567     }
 568
 569     current_time = qemu_get_clock_ns(timer_list->clock);
 570     for(;;) {
 571         ts = timer_list->active_timers;
 572         if (!timer_expired_ns(ts, current_time)) {
 573             break;
 574         }
 575         /* remove timer from the list before calling the callback */
 576         timer_list->active_timers = ts->next;
 577         ts->next = NULL;
 578
 579         /* run the callback (the timer list can be modified) */
 580         ts->cb(ts->opaque);
 581         progress = true;
 582     }
 583     return progress;
 584 }
 585
 586 bool qemu_run_timers(QEMUClock *clock)
 587 {
 588     return timerlist_run_timers(clock->main_loop_timerlist);
 589 }
 590
 591 void timerlistgroup_init(QEMUTimerListGroup *tlg,
 592                          QEMUTimerListNotifyCB *cb, void *opaque)
 593 {
 594     QEMUClockType type;
 595     for (type = 0; type < QEMU_CLOCK_MAX; type++) {
 596         tlg->tl[type] = timerlist_new(type, cb, opaque);
 597     }
 598 }
 599
 600 void timerlistgroup_deinit(QEMUTimerListGroup *tlg)
 601 {
 602     QEMUClockType type;
 603     for (type = 0; type < QEMU_CLOCK_MAX; type++) {
 604         timerlist_free(tlg->tl[type]);
 605     }
 606 }
 607
 608 bool timerlistgroup_run_timers(QEMUTimerListGroup *tlg)
 609 {
 610     QEMUClockType type;
 611     bool progress = false;
 612     for (type = 0; type < QEMU_CLOCK_MAX; type++) {
 613         progress |= timerlist_run_timers(tlg->tl[type]);
 614     }
 615     return progress;
 616 }
 617
 618 int64_t timerlistgroup_deadline_ns(QEMUTimerListGroup *tlg)
 619 {
 620     int64_t deadline = -1;
 621     QEMUClockType type;
 622     for (type = 0; type < QEMU_CLOCK_MAX; type++) {
 623         if (qemu_clock_use_for_deadline(tlg->tl[type]->clock)) {
 624             deadline = qemu_soonest_timeout(deadline,
 625                                             timerlist_deadline_ns(
 626                                                 tlg->tl[type]));
 627         }
 628     }
 629     return deadline;
 630 }
 631
 632 int64_t qemu_get_clock_ns(QEMUClock *clock)
 633 {
 634     int64_t now, last;
 635
 636     switch(clock->type) {
 637     case QEMU_CLOCK_REALTIME:
 638         return get_clock();
 639     default:
 640     case QEMU_CLOCK_VIRTUAL:
 641         if (use_icount) {
 642             return cpu_get_icount();
 643         } else {
 644             return cpu_get_clock();
 645         }
 646     case QEMU_CLOCK_HOST:
 647         now = get_clock_realtime();
 648         last = clock->last;
 649         clock->last = now;
 650         if (now < last) {
 651             notifier_list_notify(&clock->reset_notifiers, &now);
 652         }
 653         return now;
 654     }
 655 }
 656
 657 void qemu_register_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 658 {
 659     notifier_list_add(&clock->reset_notifiers, notifier);
 660 }
 661
 662 void qemu_unregister_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 663 {
 664     notifier_remove(notifier);
 665 }
 666
 667 void init_clocks(void)
 668 {
 669     QEMUClockType type;
 670     for (type = 0; type < QEMU_CLOCK_MAX; type++) {
 671         if (!qemu_clocks[type]) {
 672             qemu_clocks[type] = qemu_clock_new(type);
 673             main_loop_tlg.tl[type] = qemu_clocks[type]->main_loop_timerlist;
 674         }
 675     }
 676
 677 #ifdef CONFIG_PRCTL_PR_SET_TIMERSLACK
 678     prctl(PR_SET_TIMERSLACK, 1, 0, 0, 0);
 679 #endif
 680 }
 681
 682 uint64_t timer_expire_time_ns(QEMUTimer *ts)
 683 {
 684     return timer_pending(ts) ? ts->expire_time : -1;
 685 }
 686
 687 bool qemu_run_all_timers(void)
 688 {
 689     bool progress = false;
 690     alarm_timer->pending = false;
 691
 692     /* vm time timers */
 693     QEMUClockType type;
 694     for (type = 0; type < QEMU_CLOCK_MAX; type++) {
 695         progress |= qemu_run_timers(qemu_clock_ptr(type));
 696     }
 697
 698     /* rearm timer, if not periodic */
 699     if (alarm_timer->expired) {
 700         alarm_timer->expired = false;
 701         qemu_rearm_alarm_timer(alarm_timer);
 702     }
 703
 704     return progress;
 705 }
 706
 707 #ifdef _WIN32
 708 static void CALLBACK host_alarm_handler(PVOID lpParam, BOOLEAN unused)
 709 #else
 710 static void host_alarm_handler(int host_signum)
 711 #endif
 712 {
 713     struct qemu_alarm_timer *t = alarm_timer;
 714     if (!t)
 715         return;
 716
 717     t->expired = true;
 718     t->pending = true;
 719     qemu_notify_event();
 720 }
 721
 722 #if defined(__linux__)
 723
 724 #include "qemu/compatfd.h"
 725
 726 static int dynticks_start_timer(struct qemu_alarm_timer *t)
 727 {
 728     struct sigevent ev;
 729     timer_t host_timer;
 730     struct sigaction act;
 731
 732     sigfillset(&act.sa_mask);
 733     act.sa_flags = 0;
 734     act.sa_handler = host_alarm_handler;
 735
 736     sigaction(SIGALRM, &act, NULL);
 737
 738     /*
 739      * Initialize ev struct to 0 to avoid valgrind complaining
 740      * about uninitialized data in timer_create call
 741      */
 742     memset(&ev, 0, sizeof(ev));
 743     ev.sigev_value.sival_int = 0;
 744     ev.sigev_notify = SIGEV_SIGNAL;
 745 #ifdef CONFIG_SIGEV_THREAD_ID
 746     if (qemu_signalfd_available()) {
 747         ev.sigev_notify = SIGEV_THREAD_ID;
 748         ev._sigev_un._tid = qemu_get_thread_id();
 749     }
 750 #endif /* CONFIG_SIGEV_THREAD_ID */
 751     ev.sigev_signo = SIGALRM;
 752
 753     if (timer_create(CLOCK_REALTIME, &ev, &host_timer)) {
 754         perror("timer_create");
 755         return -1;
 756     }
 757
 758     t->timer = host_timer;
 759
 760     return 0;
 761 }
 762
 763 static void dynticks_stop_timer(struct qemu_alarm_timer *t)
 764 {
 765     timer_t host_timer = t->timer;
 766
 767     timer_delete(host_timer);
 768 }
 769
 770 static void dynticks_rearm_timer(struct qemu_alarm_timer *t,
 771                                  int64_t nearest_delta_ns)
 772 {
 773     timer_t host_timer = t->timer;
 774     struct itimerspec timeout;
 775     int64_t current_ns;
 776
 777     if (nearest_delta_ns < MIN_TIMER_REARM_NS)
 778         nearest_delta_ns = MIN_TIMER_REARM_NS;
 779
 780     /* check whether a timer is already running */
 781     if (timer_gettime(host_timer, &timeout)) {
 782         perror("gettime");
 783         fprintf(stderr, "Internal timer error: aborting\n");
 784         exit(1);
 785     }
 786     current_ns = timeout.it_value.tv_sec * 1000000000LL + timeout.it_value.tv_nsec;
 787     if (current_ns && current_ns <= nearest_delta_ns)
 788         return;
 789
 790     timeout.it_interval.tv_sec = 0;
 791     timeout.it_interval.tv_nsec = 0; /* 0 for one-shot timer */
 792     timeout.it_value.tv_sec =  nearest_delta_ns / 1000000000;
 793     timeout.it_value.tv_nsec = nearest_delta_ns % 1000000000;
 794     if (timer_settime(host_timer, 0 /* RELATIVE */, &timeout, NULL)) {
 795         perror("settime");
 796         fprintf(stderr, "Internal timer error: aborting\n");
 797         exit(1);
 798     }
 799 }
 800
 801 #endif /* defined(__linux__) */
 802
 803 #if !defined(_WIN32)
 804
 805 static int unix_start_timer(struct qemu_alarm_timer *t)
 806 {
 807     struct sigaction act;
 808
 809     /* timer signal */
 810     sigfillset(&act.sa_mask);
 811     act.sa_flags = 0;
 812     act.sa_handler = host_alarm_handler;
 813
 814     sigaction(SIGALRM, &act, NULL);
 815     return 0;
 816 }
 817
 818 static void unix_rearm_timer(struct qemu_alarm_timer *t,
 819                              int64_t nearest_delta_ns)
 820 {
 821     struct itimerval itv;
 822     int err;
 823
 824     if (nearest_delta_ns < MIN_TIMER_REARM_NS)
 825         nearest_delta_ns = MIN_TIMER_REARM_NS;
 826
 827     itv.it_interval.tv_sec = 0;
 828     itv.it_interval.tv_usec = 0; /* 0 for one-shot timer */
 829     itv.it_value.tv_sec =  nearest_delta_ns / 1000000000;
 830     itv.it_value.tv_usec = (nearest_delta_ns % 1000000000) / 1000;
 831     err = setitimer(ITIMER_REAL, &itv, NULL);
 832     if (err) {
 833         perror("setitimer");
 834         fprintf(stderr, "Internal timer error: aborting\n");
 835         exit(1);
 836     }
 837 }
 838
 839 static void unix_stop_timer(struct qemu_alarm_timer *t)
 840 {
 841     struct itimerval itv;
 842
 843     memset(&itv, 0, sizeof(itv));
 844     setitimer(ITIMER_REAL, &itv, NULL);
 845 }
 846
 847 #endif /* !defined(_WIN32) */
 848
 849
 850 #ifdef _WIN32
 851
 852 static MMRESULT mm_timer;
 853 static TIMECAPS mm_tc;
 854
 855 static void CALLBACK mm_alarm_handler(UINT uTimerID, UINT uMsg,
 856                                       DWORD_PTR dwUser, DWORD_PTR dw1,
 857                                       DWORD_PTR dw2)
 858 {
 859     struct qemu_alarm_timer *t = alarm_timer;
 860     if (!t) {
 861         return;
 862     }
 863     t->expired = true;
 864     t->pending = true;
 865     qemu_notify_event();
 866 }
 867
 868 static int mm_start_timer(struct qemu_alarm_timer *t)
 869 {
 870     timeGetDevCaps(&mm_tc, sizeof(mm_tc));
 871     return 0;
 872 }
 873
 874 static void mm_stop_timer(struct qemu_alarm_timer *t)
 875 {
 876     if (mm_timer) {
 877         timeKillEvent(mm_timer);
 878     }
 879 }
 880
 881 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta)
 882 {
 883     int64_t nearest_delta_ms = delta / 1000000;
 884     if (nearest_delta_ms < mm_tc.wPeriodMin) {
 885         nearest_delta_ms = mm_tc.wPeriodMin;
 886     } else if (nearest_delta_ms > mm_tc.wPeriodMax) {
 887         nearest_delta_ms = mm_tc.wPeriodMax;
 888     }
 889
 890     if (mm_timer) {
 891         timeKillEvent(mm_timer);
 892     }
 893     mm_timer = timeSetEvent((UINT)nearest_delta_ms,
 894                             mm_tc.wPeriodMin,
 895                             mm_alarm_handler,
 896                             (DWORD_PTR)t,
 897                             TIME_ONESHOT | TIME_CALLBACK_FUNCTION);
 898
 899     if (!mm_timer) {
 900         fprintf(stderr, "Failed to re-arm win32 alarm timer\n");
 901         timeEndPeriod(mm_tc.wPeriodMin);
 902         exit(1);
 903     }
 904 }
 905
 906 static int win32_start_timer(struct qemu_alarm_timer *t)
 907 {
 908     HANDLE hTimer;
 909     BOOLEAN success;
 910
 911     /* If you call ChangeTimerQueueTimer on a one-shot timer (its period
 912        is zero) that has already expired, the timer is not updated.  Since
 913        creating a new timer is relatively expensive, set a bogus one-hour
 914        interval in the dynticks case.  */
 915     success = CreateTimerQueueTimer(&hTimer,
 916                           NULL,
 917                           host_alarm_handler,
 918                           t,
 919                           1,
 920                           3600000,
 921                           WT_EXECUTEINTIMERTHREAD);
 922
 923     if (!success) {
 924         fprintf(stderr, "Failed to initialize win32 alarm timer: %ld\n",
 925                 GetLastError());
 926         return -1;
 927     }
 928
 929     t->timer = hTimer;
 930     return 0;
 931 }
 932
 933 static void win32_stop_timer(struct qemu_alarm_timer *t)
 934 {
 935     HANDLE hTimer = t->timer;
 936
 937     if (hTimer) {
 938         DeleteTimerQueueTimer(NULL, hTimer, NULL);
 939     }
 940 }
 941
 942 static void win32_rearm_timer(struct qemu_alarm_timer *t,
 943                               int64_t nearest_delta_ns)
 944 {
 945     HANDLE hTimer = t->timer;
 946     int64_t nearest_delta_ms;
 947     BOOLEAN success;
 948
 949     nearest_delta_ms = nearest_delta_ns / 1000000;
 950     if (nearest_delta_ms < 1) {
 951         nearest_delta_ms = 1;
 952     }
 953     /* ULONG_MAX can be 32 bit */
 954     if (nearest_delta_ms > ULONG_MAX) {
 955         nearest_delta_ms = ULONG_MAX;
 956     }
 957     success = ChangeTimerQueueTimer(NULL,
 958                                     hTimer,
 959                                     (unsigned long) nearest_delta_ms,
 960                                     3600000);
 961
 962     if (!success) {
 963         fprintf(stderr, "Failed to rearm win32 alarm timer: %ld\n",
 964                 GetLastError());
 965         exit(-1);
 966     }
 967
 968 }
 969
 970 #endif /* _WIN32 */
 971
 972 static void quit_timers(void)
 973 {
 974     struct qemu_alarm_timer *t = alarm_timer;
 975     alarm_timer = NULL;
 976     t->stop(t);
 977 }
 978
 979 #ifdef CONFIG_POSIX
 980 static void reinit_timers(void)
 981 {
 982     struct qemu_alarm_timer *t = alarm_timer;
 983     t->stop(t);
 984     if (t->start(t)) {
 985         fprintf(stderr, "Internal timer error: aborting\n");
 986         exit(1);
 987     }
 988     qemu_rearm_alarm_timer(t);
 989 }
 990 #endif /* CONFIG_POSIX */
 991
 992 int init_timer_alarm(void)
 993 {
 994     struct qemu_alarm_timer *t = NULL;
 995     int i, err = -1;
 996
 997     if (alarm_timer) {
 998         return 0;
 999     }
1000
1001     for (i = 0; alarm_timers[i].name; i++) {
1002         t = &alarm_timers[i];
1003
1004         err = t->start(t);
1005         if (!err)
1006             break;
1007     }
1008
1009     if (err) {
1010         err = -ENOENT;
1011         goto fail;
1012     }
1013
1014     atexit(quit_timers);
1015 #ifdef CONFIG_POSIX
1016     pthread_atfork(NULL, NULL, reinit_timers);
1017 #endif
1018     alarm_timer = t;
1019     return 0;
1020
1021 fail:
1022     return err;
1023 }
1024