qemu/monitor/monitor.c
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   1/*
   2 * QEMU monitor
   3 *
   4 * Copyright (c) 2003-2004 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 "qemu/osdep.h"
  26#include "monitor-internal.h"
  27#include "qapi/error.h"
  28#include "qapi/opts-visitor.h"
  29#include "qapi/qapi-emit-events.h"
  30#include "qapi/qapi-visit-control.h"
  31#include "qapi/qmp/qdict.h"
  32#include "qemu/error-report.h"
  33#include "qemu/option.h"
  34#include "sysemu/qtest.h"
  35#include "trace.h"
  36
  37/*
  38 * To prevent flooding clients, events can be throttled. The
  39 * throttling is calculated globally, rather than per-Monitor
  40 * instance.
  41 */
  42typedef struct MonitorQAPIEventState {
  43    QAPIEvent event;    /* Throttling state for this event type and... */
  44    QDict *data;        /* ... data, see qapi_event_throttle_equal() */
  45    QEMUTimer *timer;   /* Timer for handling delayed events */
  46    QDict *qdict;       /* Delayed event (if any) */
  47} MonitorQAPIEventState;
  48
  49typedef struct {
  50    int64_t rate;       /* Minimum time (in ns) between two events */
  51} MonitorQAPIEventConf;
  52
  53/* Shared monitor I/O thread */
  54IOThread *mon_iothread;
  55
  56/* Coroutine to dispatch the requests received from I/O thread */
  57Coroutine *qmp_dispatcher_co;
  58
  59/* Set to true when the dispatcher coroutine should terminate */
  60bool qmp_dispatcher_co_shutdown;
  61
  62/*
  63 * qmp_dispatcher_co_busy is used for synchronisation between the
  64 * monitor thread and the main thread to ensure that the dispatcher
  65 * coroutine never gets scheduled a second time when it's already
  66 * scheduled (scheduling the same coroutine twice is forbidden).
  67 *
  68 * It is true if the coroutine is active and processing requests.
  69 * Additional requests may then be pushed onto mon->qmp_requests,
  70 * and @qmp_dispatcher_co_shutdown may be set without further ado.
  71 * @qmp_dispatcher_co_busy must not be woken up in this case.
  72 *
  73 * If false, you also have to set @qmp_dispatcher_co_busy to true and
  74 * wake up @qmp_dispatcher_co after pushing the new requests.
  75 *
  76 * The coroutine will automatically change this variable back to false
  77 * before it yields.  Nobody else may set the variable to false.
  78 *
  79 * Access must be atomic for thread safety.
  80 */
  81bool qmp_dispatcher_co_busy;
  82
  83/*
  84 * Protects mon_list, monitor_qapi_event_state, coroutine_mon,
  85 * monitor_destroyed.
  86 */
  87QemuMutex monitor_lock;
  88static GHashTable *monitor_qapi_event_state;
  89static GHashTable *coroutine_mon; /* Maps Coroutine* to Monitor* */
  90
  91MonitorList mon_list;
  92int mon_refcount;
  93static bool monitor_destroyed;
  94
  95Monitor *monitor_cur(void)
  96{
  97    Monitor *mon;
  98
  99    qemu_mutex_lock(&monitor_lock);
 100    mon = g_hash_table_lookup(coroutine_mon, qemu_coroutine_self());
 101    qemu_mutex_unlock(&monitor_lock);
 102
 103    return mon;
 104}
 105
 106/**
 107 * Sets a new current monitor and returns the old one.
 108 *
 109 * If a non-NULL monitor is set for a coroutine, another call
 110 * resetting it to NULL is required before the coroutine terminates,
 111 * otherwise a stale entry would remain in the hash table.
 112 */
 113Monitor *monitor_set_cur(Coroutine *co, Monitor *mon)
 114{
 115    Monitor *old_monitor = monitor_cur();
 116
 117    qemu_mutex_lock(&monitor_lock);
 118    if (mon) {
 119        g_hash_table_replace(coroutine_mon, co, mon);
 120    } else {
 121        g_hash_table_remove(coroutine_mon, co);
 122    }
 123    qemu_mutex_unlock(&monitor_lock);
 124
 125    return old_monitor;
 126}
 127
 128/**
 129 * Is the current monitor, if any, a QMP monitor?
 130 */
 131bool monitor_cur_is_qmp(void)
 132{
 133    Monitor *cur_mon = monitor_cur();
 134
 135    return cur_mon && monitor_is_qmp(cur_mon);
 136}
 137
 138/**
 139 * Is @mon is using readline?
 140 * Note: not all HMP monitors use readline, e.g., gdbserver has a
 141 * non-interactive HMP monitor, so readline is not used there.
 142 */
 143static inline bool monitor_uses_readline(const MonitorHMP *mon)
 144{
 145    return mon->use_readline;
 146}
 147
 148static inline bool monitor_is_hmp_non_interactive(const Monitor *mon)
 149{
 150    if (monitor_is_qmp(mon)) {
 151        return false;
 152    }
 153
 154    return !monitor_uses_readline(container_of(mon, MonitorHMP, common));
 155}
 156
 157static void monitor_flush_locked(Monitor *mon);
 158
 159static gboolean monitor_unblocked(void *do_not_use, GIOCondition cond,
 160                                  void *opaque)
 161{
 162    Monitor *mon = opaque;
 163
 164    qemu_mutex_lock(&mon->mon_lock);
 165    mon->out_watch = 0;
 166    monitor_flush_locked(mon);
 167    qemu_mutex_unlock(&mon->mon_lock);
 168    return FALSE;
 169}
 170
 171/* Caller must hold mon->mon_lock */
 172static void monitor_flush_locked(Monitor *mon)
 173{
 174    int rc;
 175    size_t len;
 176    const char *buf;
 177
 178    if (mon->skip_flush) {
 179        return;
 180    }
 181
 182    buf = mon->outbuf->str;
 183    len = mon->outbuf->len;
 184
 185    if (len && !mon->mux_out) {
 186        rc = qemu_chr_fe_write(&mon->chr, (const uint8_t *) buf, len);
 187        if ((rc < 0 && errno != EAGAIN) || (rc == len)) {
 188            /* all flushed or error */
 189            g_string_truncate(mon->outbuf, 0);
 190            return;
 191        }
 192        if (rc > 0) {
 193            /* partial write */
 194            g_string_erase(mon->outbuf, 0, rc);
 195        }
 196        if (mon->out_watch == 0) {
 197            mon->out_watch =
 198                qemu_chr_fe_add_watch(&mon->chr, G_IO_OUT | G_IO_HUP,
 199                                      monitor_unblocked, mon);
 200        }
 201    }
 202}
 203
 204void monitor_flush(Monitor *mon)
 205{
 206    qemu_mutex_lock(&mon->mon_lock);
 207    monitor_flush_locked(mon);
 208    qemu_mutex_unlock(&mon->mon_lock);
 209}
 210
 211/* flush at every end of line */
 212int monitor_puts(Monitor *mon, const char *str)
 213{
 214    int i;
 215    char c;
 216
 217    qemu_mutex_lock(&mon->mon_lock);
 218    for (i = 0; str[i]; i++) {
 219        c = str[i];
 220        if (c == '\n') {
 221            g_string_append_c(mon->outbuf, '\r');
 222        }
 223        g_string_append_c(mon->outbuf, c);
 224        if (c == '\n') {
 225            monitor_flush_locked(mon);
 226        }
 227    }
 228    qemu_mutex_unlock(&mon->mon_lock);
 229
 230    return i;
 231}
 232
 233int monitor_vprintf(Monitor *mon, const char *fmt, va_list ap)
 234{
 235    char *buf;
 236    int n;
 237
 238    if (!mon) {
 239        return -1;
 240    }
 241
 242    if (monitor_is_qmp(mon)) {
 243        return -1;
 244    }
 245
 246    buf = g_strdup_vprintf(fmt, ap);
 247    n = monitor_puts(mon, buf);
 248    g_free(buf);
 249    return n;
 250}
 251
 252int monitor_printf(Monitor *mon, const char *fmt, ...)
 253{
 254    int ret;
 255
 256    va_list ap;
 257    va_start(ap, fmt);
 258    ret = monitor_vprintf(mon, fmt, ap);
 259    va_end(ap);
 260    return ret;
 261}
 262
 263void monitor_printc(Monitor *mon, int c)
 264{
 265    monitor_printf(mon, "'");
 266    switch(c) {
 267    case '\'':
 268        monitor_printf(mon, "\\'");
 269        break;
 270    case '\\':
 271        monitor_printf(mon, "\\\\");
 272        break;
 273    case '\n':
 274        monitor_printf(mon, "\\n");
 275        break;
 276    case '\r':
 277        monitor_printf(mon, "\\r");
 278        break;
 279    default:
 280        if (c >= 32 && c <= 126) {
 281            monitor_printf(mon, "%c", c);
 282        } else {
 283            monitor_printf(mon, "\\x%02x", c);
 284        }
 285        break;
 286    }
 287    monitor_printf(mon, "'");
 288}
 289
 290/*
 291 * Print to current monitor if we have one, else to stderr.
 292 */
 293int error_vprintf(const char *fmt, va_list ap)
 294{
 295    Monitor *cur_mon = monitor_cur();
 296
 297    if (cur_mon && !monitor_cur_is_qmp()) {
 298        return monitor_vprintf(cur_mon, fmt, ap);
 299    }
 300    return vfprintf(stderr, fmt, ap);
 301}
 302
 303int error_vprintf_unless_qmp(const char *fmt, va_list ap)
 304{
 305    Monitor *cur_mon = monitor_cur();
 306
 307    if (!cur_mon) {
 308        return vfprintf(stderr, fmt, ap);
 309    }
 310    if (!monitor_cur_is_qmp()) {
 311        return monitor_vprintf(cur_mon, fmt, ap);
 312    }
 313    return -1;
 314}
 315
 316int error_printf_unless_qmp(const char *fmt, ...)
 317{
 318    va_list ap;
 319    int ret;
 320
 321    va_start(ap, fmt);
 322    ret = error_vprintf_unless_qmp(fmt, ap);
 323    va_end(ap);
 324    return ret;
 325}
 326
 327static MonitorQAPIEventConf monitor_qapi_event_conf[QAPI_EVENT__MAX] = {
 328    /* Limit guest-triggerable events to 1 per second */
 329    [QAPI_EVENT_RTC_CHANGE]        = { 1000 * SCALE_MS },
 330    [QAPI_EVENT_WATCHDOG]          = { 1000 * SCALE_MS },
 331    [QAPI_EVENT_BALLOON_CHANGE]    = { 1000 * SCALE_MS },
 332    [QAPI_EVENT_QUORUM_REPORT_BAD] = { 1000 * SCALE_MS },
 333    [QAPI_EVENT_QUORUM_FAILURE]    = { 1000 * SCALE_MS },
 334    [QAPI_EVENT_VSERPORT_CHANGE]   = { 1000 * SCALE_MS },
 335    [QAPI_EVENT_MEMORY_DEVICE_SIZE_CHANGE] = { 1000 * SCALE_MS },
 336};
 337
 338/*
 339 * Return the clock to use for recording an event's time.
 340 * It's QEMU_CLOCK_REALTIME, except for qtests it's
 341 * QEMU_CLOCK_VIRTUAL, to support testing rate limits.
 342 * Beware: result is invalid before configure_accelerator().
 343 */
 344static inline QEMUClockType monitor_get_event_clock(void)
 345{
 346    return qtest_enabled() ? QEMU_CLOCK_VIRTUAL : QEMU_CLOCK_REALTIME;
 347}
 348
 349/*
 350 * Broadcast an event to all monitors.
 351 * @qdict is the event object.  Its member "event" must match @event.
 352 * Caller must hold monitor_lock.
 353 */
 354static void monitor_qapi_event_emit(QAPIEvent event, QDict *qdict)
 355{
 356    Monitor *mon;
 357    MonitorQMP *qmp_mon;
 358
 359    trace_monitor_protocol_event_emit(event, qdict);
 360    QTAILQ_FOREACH(mon, &mon_list, entry) {
 361        if (!monitor_is_qmp(mon)) {
 362            continue;
 363        }
 364
 365        qmp_mon = container_of(mon, MonitorQMP, common);
 366        if (qmp_mon->commands != &qmp_cap_negotiation_commands) {
 367            qmp_send_response(qmp_mon, qdict);
 368        }
 369    }
 370}
 371
 372static void monitor_qapi_event_handler(void *opaque);
 373
 374/*
 375 * Queue a new event for emission to Monitor instances,
 376 * applying any rate limiting if required.
 377 */
 378static void
 379monitor_qapi_event_queue_no_reenter(QAPIEvent event, QDict *qdict)
 380{
 381    MonitorQAPIEventConf *evconf;
 382    MonitorQAPIEventState *evstate;
 383
 384    assert(event < QAPI_EVENT__MAX);
 385    evconf = &monitor_qapi_event_conf[event];
 386    trace_monitor_protocol_event_queue(event, qdict, evconf->rate);
 387
 388    QEMU_LOCK_GUARD(&monitor_lock);
 389
 390    if (!evconf->rate) {
 391        /* Unthrottled event */
 392        monitor_qapi_event_emit(event, qdict);
 393    } else {
 394        QDict *data = qobject_to(QDict, qdict_get(qdict, "data"));
 395        MonitorQAPIEventState key = { .event = event, .data = data };
 396
 397        evstate = g_hash_table_lookup(monitor_qapi_event_state, &key);
 398        assert(!evstate || timer_pending(evstate->timer));
 399
 400        if (evstate) {
 401            /*
 402             * Timer is pending for (at least) evconf->rate ns after
 403             * last send.  Store event for sending when timer fires,
 404             * replacing a prior stored event if any.
 405             */
 406            qobject_unref(evstate->qdict);
 407            evstate->qdict = qobject_ref(qdict);
 408        } else {
 409            /*
 410             * Last send was (at least) evconf->rate ns ago.
 411             * Send immediately, and arm the timer to call
 412             * monitor_qapi_event_handler() in evconf->rate ns.  Any
 413             * events arriving before then will be delayed until then.
 414             */
 415            int64_t now = qemu_clock_get_ns(monitor_get_event_clock());
 416
 417            monitor_qapi_event_emit(event, qdict);
 418
 419            evstate = g_new(MonitorQAPIEventState, 1);
 420            evstate->event = event;
 421            evstate->data = qobject_ref(data);
 422            evstate->qdict = NULL;
 423            evstate->timer = timer_new_ns(monitor_get_event_clock(),
 424                                          monitor_qapi_event_handler,
 425                                          evstate);
 426            g_hash_table_add(monitor_qapi_event_state, evstate);
 427            timer_mod_ns(evstate->timer, now + evconf->rate);
 428        }
 429    }
 430}
 431
 432void qapi_event_emit(QAPIEvent event, QDict *qdict)
 433{
 434    /*
 435     * monitor_qapi_event_queue_no_reenter() is not reentrant: it
 436     * would deadlock on monitor_lock.  Work around by queueing
 437     * events in thread-local storage.
 438     * TODO: remove this, make it re-enter safe.
 439     */
 440    typedef struct MonitorQapiEvent {
 441        QAPIEvent event;
 442        QDict *qdict;
 443        QSIMPLEQ_ENTRY(MonitorQapiEvent) entry;
 444    } MonitorQapiEvent;
 445    static __thread QSIMPLEQ_HEAD(, MonitorQapiEvent) event_queue;
 446    static __thread bool reentered;
 447    MonitorQapiEvent *ev;
 448
 449    if (!reentered) {
 450        QSIMPLEQ_INIT(&event_queue);
 451    }
 452
 453    ev = g_new(MonitorQapiEvent, 1);
 454    ev->qdict = qobject_ref(qdict);
 455    ev->event = event;
 456    QSIMPLEQ_INSERT_TAIL(&event_queue, ev, entry);
 457    if (reentered) {
 458        return;
 459    }
 460
 461    reentered = true;
 462
 463    while ((ev = QSIMPLEQ_FIRST(&event_queue)) != NULL) {
 464        QSIMPLEQ_REMOVE_HEAD(&event_queue, entry);
 465        monitor_qapi_event_queue_no_reenter(ev->event, ev->qdict);
 466        qobject_unref(ev->qdict);
 467        g_free(ev);
 468    }
 469
 470    reentered = false;
 471}
 472
 473/*
 474 * This function runs evconf->rate ns after sending a throttled
 475 * event.
 476 * If another event has since been stored, send it.
 477 */
 478static void monitor_qapi_event_handler(void *opaque)
 479{
 480    MonitorQAPIEventState *evstate = opaque;
 481    MonitorQAPIEventConf *evconf = &monitor_qapi_event_conf[evstate->event];
 482
 483    trace_monitor_protocol_event_handler(evstate->event, evstate->qdict);
 484    QEMU_LOCK_GUARD(&monitor_lock);
 485
 486    if (evstate->qdict) {
 487        int64_t now = qemu_clock_get_ns(monitor_get_event_clock());
 488
 489        monitor_qapi_event_emit(evstate->event, evstate->qdict);
 490        qobject_unref(evstate->qdict);
 491        evstate->qdict = NULL;
 492        timer_mod_ns(evstate->timer, now + evconf->rate);
 493    } else {
 494        g_hash_table_remove(monitor_qapi_event_state, evstate);
 495        qobject_unref(evstate->data);
 496        timer_free(evstate->timer);
 497        g_free(evstate);
 498    }
 499}
 500
 501static unsigned int qapi_event_throttle_hash(const void *key)
 502{
 503    const MonitorQAPIEventState *evstate = key;
 504    unsigned int hash = evstate->event * 255;
 505
 506    if (evstate->event == QAPI_EVENT_VSERPORT_CHANGE) {
 507        hash += g_str_hash(qdict_get_str(evstate->data, "id"));
 508    }
 509
 510    if (evstate->event == QAPI_EVENT_QUORUM_REPORT_BAD) {
 511        hash += g_str_hash(qdict_get_str(evstate->data, "node-name"));
 512    }
 513
 514    if (evstate->event == QAPI_EVENT_MEMORY_DEVICE_SIZE_CHANGE) {
 515        hash += g_str_hash(qdict_get_str(evstate->data, "qom-path"));
 516    }
 517
 518    return hash;
 519}
 520
 521static gboolean qapi_event_throttle_equal(const void *a, const void *b)
 522{
 523    const MonitorQAPIEventState *eva = a;
 524    const MonitorQAPIEventState *evb = b;
 525
 526    if (eva->event != evb->event) {
 527        return FALSE;
 528    }
 529
 530    if (eva->event == QAPI_EVENT_VSERPORT_CHANGE) {
 531        return !strcmp(qdict_get_str(eva->data, "id"),
 532                       qdict_get_str(evb->data, "id"));
 533    }
 534
 535    if (eva->event == QAPI_EVENT_QUORUM_REPORT_BAD) {
 536        return !strcmp(qdict_get_str(eva->data, "node-name"),
 537                       qdict_get_str(evb->data, "node-name"));
 538    }
 539
 540    if (eva->event == QAPI_EVENT_MEMORY_DEVICE_SIZE_CHANGE) {
 541        return !strcmp(qdict_get_str(eva->data, "qom-path"),
 542                       qdict_get_str(evb->data, "qom-path"));
 543    }
 544
 545    return TRUE;
 546}
 547
 548int monitor_suspend(Monitor *mon)
 549{
 550    if (monitor_is_hmp_non_interactive(mon)) {
 551        return -ENOTTY;
 552    }
 553
 554    qatomic_inc(&mon->suspend_cnt);
 555
 556    if (mon->use_io_thread) {
 557        /*
 558         * Kick I/O thread to make sure this takes effect.  It'll be
 559         * evaluated again in prepare() of the watch object.
 560         */
 561        aio_notify(iothread_get_aio_context(mon_iothread));
 562    }
 563
 564    trace_monitor_suspend(mon, 1);
 565    return 0;
 566}
 567
 568static void monitor_accept_input(void *opaque)
 569{
 570    Monitor *mon = opaque;
 571
 572    qemu_chr_fe_accept_input(&mon->chr);
 573}
 574
 575void monitor_resume(Monitor *mon)
 576{
 577    if (monitor_is_hmp_non_interactive(mon)) {
 578        return;
 579    }
 580
 581    if (qatomic_dec_fetch(&mon->suspend_cnt) == 0) {
 582        AioContext *ctx;
 583
 584        if (mon->use_io_thread) {
 585            ctx = iothread_get_aio_context(mon_iothread);
 586        } else {
 587            ctx = qemu_get_aio_context();
 588        }
 589
 590        if (!monitor_is_qmp(mon)) {
 591            MonitorHMP *hmp_mon = container_of(mon, MonitorHMP, common);
 592            assert(hmp_mon->rs);
 593            readline_show_prompt(hmp_mon->rs);
 594        }
 595
 596        aio_bh_schedule_oneshot(ctx, monitor_accept_input, mon);
 597    }
 598
 599    trace_monitor_suspend(mon, -1);
 600}
 601
 602int monitor_can_read(void *opaque)
 603{
 604    Monitor *mon = opaque;
 605
 606    return !qatomic_mb_read(&mon->suspend_cnt);
 607}
 608
 609void monitor_list_append(Monitor *mon)
 610{
 611    qemu_mutex_lock(&monitor_lock);
 612    /*
 613     * This prevents inserting new monitors during monitor_cleanup().
 614     * A cleaner solution would involve the main thread telling other
 615     * threads to terminate, waiting for their termination.
 616     */
 617    if (!monitor_destroyed) {
 618        QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
 619        mon = NULL;
 620    }
 621    qemu_mutex_unlock(&monitor_lock);
 622
 623    if (mon) {
 624        monitor_data_destroy(mon);
 625        g_free(mon);
 626    }
 627}
 628
 629static void monitor_iothread_init(void)
 630{
 631    mon_iothread = iothread_create("mon_iothread", &error_abort);
 632}
 633
 634void monitor_data_init(Monitor *mon, bool is_qmp, bool skip_flush,
 635                       bool use_io_thread)
 636{
 637    if (use_io_thread && !mon_iothread) {
 638        monitor_iothread_init();
 639    }
 640    qemu_mutex_init(&mon->mon_lock);
 641    mon->is_qmp = is_qmp;
 642    mon->outbuf = g_string_new(NULL);
 643    mon->skip_flush = skip_flush;
 644    mon->use_io_thread = use_io_thread;
 645}
 646
 647void monitor_data_destroy(Monitor *mon)
 648{
 649    g_free(mon->mon_cpu_path);
 650    qemu_chr_fe_deinit(&mon->chr, false);
 651    if (monitor_is_qmp(mon)) {
 652        monitor_data_destroy_qmp(container_of(mon, MonitorQMP, common));
 653    } else {
 654        readline_free(container_of(mon, MonitorHMP, common)->rs);
 655    }
 656    g_string_free(mon->outbuf, true);
 657    qemu_mutex_destroy(&mon->mon_lock);
 658}
 659
 660void monitor_cleanup(void)
 661{
 662    /*
 663     * The dispatcher needs to stop before destroying the monitor and
 664     * the I/O thread.
 665     *
 666     * We need to poll both qemu_aio_context and iohandler_ctx to make
 667     * sure that the dispatcher coroutine keeps making progress and
 668     * eventually terminates.  qemu_aio_context is automatically
 669     * polled by calling AIO_WAIT_WHILE on it, but we must poll
 670     * iohandler_ctx manually.
 671     *
 672     * Letting the iothread continue while shutting down the dispatcher
 673     * means that new requests may still be coming in. This is okay,
 674     * we'll just leave them in the queue without sending a response
 675     * and monitor_data_destroy() will free them.
 676     */
 677    qmp_dispatcher_co_shutdown = true;
 678    if (!qatomic_xchg(&qmp_dispatcher_co_busy, true)) {
 679        aio_co_wake(qmp_dispatcher_co);
 680    }
 681
 682    AIO_WAIT_WHILE(qemu_get_aio_context(),
 683                   (aio_poll(iohandler_get_aio_context(), false),
 684                    qatomic_mb_read(&qmp_dispatcher_co_busy)));
 685
 686    /*
 687     * We need to explicitly stop the I/O thread (but not destroy it),
 688     * clean up the monitor resources, then destroy the I/O thread since
 689     * we need to unregister from chardev below in
 690     * monitor_data_destroy(), and chardev is not thread-safe yet
 691     */
 692    if (mon_iothread) {
 693        iothread_stop(mon_iothread);
 694    }
 695
 696    /* Flush output buffers and destroy monitors */
 697    qemu_mutex_lock(&monitor_lock);
 698    monitor_destroyed = true;
 699    while (!QTAILQ_EMPTY(&mon_list)) {
 700        Monitor *mon = QTAILQ_FIRST(&mon_list);
 701        QTAILQ_REMOVE(&mon_list, mon, entry);
 702        /* Permit QAPI event emission from character frontend release */
 703        qemu_mutex_unlock(&monitor_lock);
 704        monitor_flush(mon);
 705        monitor_data_destroy(mon);
 706        qemu_mutex_lock(&monitor_lock);
 707        g_free(mon);
 708    }
 709    qemu_mutex_unlock(&monitor_lock);
 710
 711    if (mon_iothread) {
 712        iothread_destroy(mon_iothread);
 713        mon_iothread = NULL;
 714    }
 715}
 716
 717static void monitor_qapi_event_init(void)
 718{
 719    monitor_qapi_event_state = g_hash_table_new(qapi_event_throttle_hash,
 720                                                qapi_event_throttle_equal);
 721}
 722
 723void monitor_init_globals(void)
 724{
 725    monitor_qapi_event_init();
 726    qemu_mutex_init(&monitor_lock);
 727    coroutine_mon = g_hash_table_new(NULL, NULL);
 728
 729    /*
 730     * The dispatcher BH must run in the main loop thread, since we
 731     * have commands assuming that context.  It would be nice to get
 732     * rid of those assumptions.
 733     */
 734    qmp_dispatcher_co = qemu_coroutine_create(monitor_qmp_dispatcher_co, NULL);
 735    qatomic_mb_set(&qmp_dispatcher_co_busy, true);
 736    aio_co_schedule(iohandler_get_aio_context(), qmp_dispatcher_co);
 737}
 738
 739int monitor_init(MonitorOptions *opts, bool allow_hmp, Error **errp)
 740{
 741    ERRP_GUARD();
 742    Chardev *chr;
 743
 744    chr = qemu_chr_find(opts->chardev);
 745    if (chr == NULL) {
 746        error_setg(errp, "chardev \"%s\" not found", opts->chardev);
 747        return -1;
 748    }
 749
 750    if (!opts->has_mode) {
 751        opts->mode = allow_hmp ? MONITOR_MODE_READLINE : MONITOR_MODE_CONTROL;
 752    }
 753
 754    switch (opts->mode) {
 755    case MONITOR_MODE_CONTROL:
 756        monitor_init_qmp(chr, opts->pretty, errp);
 757        break;
 758    case MONITOR_MODE_READLINE:
 759        if (!allow_hmp) {
 760            error_setg(errp, "Only QMP is supported");
 761            return -1;
 762        }
 763        if (opts->pretty) {
 764            error_setg(errp, "'pretty' is not compatible with HMP monitors");
 765            return -1;
 766        }
 767        monitor_init_hmp(chr, true, errp);
 768        break;
 769    default:
 770        g_assert_not_reached();
 771    }
 772
 773    return *errp ? -1 : 0;
 774}
 775
 776int monitor_init_opts(QemuOpts *opts, Error **errp)
 777{
 778    Visitor *v;
 779    MonitorOptions *options;
 780    int ret;
 781
 782    v = opts_visitor_new(opts);
 783    visit_type_MonitorOptions(v, NULL, &options, errp);
 784    visit_free(v);
 785    if (!options) {
 786        return -1;
 787    }
 788
 789    ret = monitor_init(options, true, errp);
 790    qapi_free_MonitorOptions(options);
 791    return ret;
 792}
 793
 794QemuOptsList qemu_mon_opts = {
 795    .name = "mon",
 796    .implied_opt_name = "chardev",
 797    .head = QTAILQ_HEAD_INITIALIZER(qemu_mon_opts.head),
 798    .desc = {
 799        {
 800            .name = "mode",
 801            .type = QEMU_OPT_STRING,
 802        },{
 803            .name = "chardev",
 804            .type = QEMU_OPT_STRING,
 805        },{
 806            .name = "pretty",
 807            .type = QEMU_OPT_BOOL,
 808        },
 809        { /* end of list */ }
 810    },
 811};
 812