monitor/monitor.c - third_party/qemu - Git at Google

 /*
  * QEMU monitor
  *
  * Copyright (c) 2003-2004 Fabrice Bellard
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */

 #include "qemu/osdep.h"
 #include "monitor-internal.h"
 #include "qapi/error.h"
 #include "qapi/opts-visitor.h"
 #include "qapi/qapi-emit-events.h"
 #include "qapi/qapi-visit-control.h"
 #include "qapi/qmp/qdict.h"
 #include "qapi/qmp/qstring.h"
 #include "qemu/error-report.h"
 #include "qemu/option.h"
 #include "sysemu/qtest.h"
 #include "sysemu/sysemu.h"
 #include "trace.h"

 /*
  * To prevent flooding clients, events can be throttled. The
  * throttling is calculated globally, rather than per-Monitor
  * instance.
  */
 typedef struct MonitorQAPIEventState {
     QAPIEvent event;    /* Throttling state for this event type and... */
     QDict *data;        /* ... data, see qapi_event_throttle_equal() */
     QEMUTimer *timer;   /* Timer for handling delayed events */
     QDict *qdict;       /* Delayed event (if any) */
 } MonitorQAPIEventState;

 typedef struct {
     int64_t rate;       /* Minimum time (in ns) between two events */
 } MonitorQAPIEventConf;

 /* Shared monitor I/O thread */
 IOThread *mon_iothread;

 /* Bottom half to dispatch the requests received from I/O thread */
 QEMUBH *qmp_dispatcher_bh;

 /* Protects mon_list, monitor_qapi_event_state, monitor_destroyed.  */
 QemuMutex monitor_lock;
 static GHashTable *monitor_qapi_event_state;

 MonitorList mon_list;
 int mon_refcount;
 static bool monitor_destroyed;

 __thread Monitor *cur_mon;

 /**
  * Is the current monitor, if any, a QMP monitor?
  */
 bool monitor_cur_is_qmp(void)
 {
     return cur_mon && monitor_is_qmp(cur_mon);
 }

 /**
  * Is @mon is using readline?
  * Note: not all HMP monitors use readline, e.g., gdbserver has a
  * non-interactive HMP monitor, so readline is not used there.
  */
 static inline bool monitor_uses_readline(const MonitorHMP *mon)
 {
     return mon->use_readline;
 }

 static inline bool monitor_is_hmp_non_interactive(const Monitor *mon)
 {
     if (monitor_is_qmp(mon)) {
         return false;
     }

     return !monitor_uses_readline(container_of(mon, MonitorHMP, common));
 }

 static void monitor_flush_locked(Monitor *mon);

 static gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond,
                                   void *opaque)
 {
     Monitor *mon = opaque;

     qemu_mutex_lock(&mon->mon_lock);
     mon->out_watch = 0;
     monitor_flush_locked(mon);
     qemu_mutex_unlock(&mon->mon_lock);
     return FALSE;
 }

 /* Caller must hold mon->mon_lock */
 static void monitor_flush_locked(Monitor *mon)
 {
     int rc;
     size_t len;
     const char *buf;

     if (mon->skip_flush) {
         return;
     }

     buf = qstring_get_str(mon->outbuf);
     len = qstring_get_length(mon->outbuf);

     if (len && !mon->mux_out) {
         rc = qemu_chr_fe_write(&mon->chr, (const uint8_t *) buf, len);
         if ((rc < 0 && errno != EAGAIN) || (rc == len)) {
             /* all flushed or error */
             qobject_unref(mon->outbuf);
             mon->outbuf = qstring_new();
             return;
         }
         if (rc > 0) {
             /* partial write */
             QString *tmp = qstring_from_str(buf + rc);
             qobject_unref(mon->outbuf);
             mon->outbuf = tmp;
         }
         if (mon->out_watch == 0) {
             mon->out_watch =
                 qemu_chr_fe_add_watch(&mon->chr, G_IO_OUT | G_IO_HUP,
                                       monitor_unblocked, mon);
         }
     }
 }

 void monitor_flush(Monitor *mon)
 {
     qemu_mutex_lock(&mon->mon_lock);
     monitor_flush_locked(mon);
     qemu_mutex_unlock(&mon->mon_lock);
 }

 /* flush at every end of line */
 int monitor_puts(Monitor *mon, const char *str)
 {
     int i;
     char c;

     qemu_mutex_lock(&mon->mon_lock);
     for (i = 0; str[i]; i++) {
         c = str[i];
         if (c == '\n') {
             qstring_append_chr(mon->outbuf, '\r');
         }
         qstring_append_chr(mon->outbuf, c);
         if (c == '\n') {
             monitor_flush_locked(mon);
         }
     }
     qemu_mutex_unlock(&mon->mon_lock);

     return i;
 }

 int monitor_vprintf(Monitor *mon, const char *fmt, va_list ap)
 {
     char *buf;
     int n;

     if (!mon) {
         return -1;
     }

     if (monitor_is_qmp(mon)) {
         return -1;
     }

     buf = g_strdup_vprintf(fmt, ap);
     n = monitor_puts(mon, buf);
     g_free(buf);
     return n;
 }

 int monitor_printf(Monitor *mon, const char *fmt, ...)
 {
     int ret;

     va_list ap;
     va_start(ap, fmt);
     ret = monitor_vprintf(mon, fmt, ap);
     va_end(ap);
     return ret;
 }

 /*
  * Print to current monitor if we have one, else to stderr.
  */
 int error_vprintf(const char *fmt, va_list ap)
 {
     if (cur_mon && !monitor_cur_is_qmp()) {
         return monitor_vprintf(cur_mon, fmt, ap);
     }
     return vfprintf(stderr, fmt, ap);
 }

 int error_vprintf_unless_qmp(const char *fmt, va_list ap)
 {
     if (!cur_mon) {
         return vfprintf(stderr, fmt, ap);
     }
     if (!monitor_cur_is_qmp()) {
         return monitor_vprintf(cur_mon, fmt, ap);
     }
     return -1;
 }


 static MonitorQAPIEventConf monitor_qapi_event_conf[QAPI_EVENT__MAX] = {
     /* Limit guest-triggerable events to 1 per second */
     [QAPI_EVENT_RTC_CHANGE]        = { 1000 * SCALE_MS },
     [QAPI_EVENT_WATCHDOG]          = { 1000 * SCALE_MS },
     [QAPI_EVENT_BALLOON_CHANGE]    = { 1000 * SCALE_MS },
     [QAPI_EVENT_QUORUM_REPORT_BAD] = { 1000 * SCALE_MS },
     [QAPI_EVENT_QUORUM_FAILURE]    = { 1000 * SCALE_MS },
     [QAPI_EVENT_VSERPORT_CHANGE]   = { 1000 * SCALE_MS },
 };

 /*
  * Return the clock to use for recording an event's time.
  * It's QEMU_CLOCK_REALTIME, except for qtests it's
  * QEMU_CLOCK_VIRTUAL, to support testing rate limits.
  * Beware: result is invalid before configure_accelerator().
  */
 static inline QEMUClockType monitor_get_event_clock(void)
 {
     return qtest_enabled() ? QEMU_CLOCK_VIRTUAL : QEMU_CLOCK_REALTIME;
 }

 /*
  * Broadcast an event to all monitors.
  * @qdict is the event object.  Its member "event" must match @event.
  * Caller must hold monitor_lock.
  */
 static void monitor_qapi_event_emit(QAPIEvent event, QDict *qdict)
 {
     Monitor *mon;
     MonitorQMP *qmp_mon;

     trace_monitor_protocol_event_emit(event, qdict);
     QTAILQ_FOREACH(mon, &mon_list, entry) {
         if (!monitor_is_qmp(mon)) {
             continue;
         }

         qmp_mon = container_of(mon, MonitorQMP, common);
         if (qmp_mon->commands != &qmp_cap_negotiation_commands) {
             qmp_send_response(qmp_mon, qdict);
         }
     }
 }

 static void monitor_qapi_event_handler(void *opaque);

 /*
  * Queue a new event for emission to Monitor instances,
  * applying any rate limiting if required.
  */
 static void
 monitor_qapi_event_queue_no_reenter(QAPIEvent event, QDict *qdict)
 {
     MonitorQAPIEventConf *evconf;
     MonitorQAPIEventState *evstate;

     assert(event < QAPI_EVENT__MAX);
     evconf = &monitor_qapi_event_conf[event];
     trace_monitor_protocol_event_queue(event, qdict, evconf->rate);

     qemu_mutex_lock(&monitor_lock);

     if (!evconf->rate) {
         /* Unthrottled event */
         monitor_qapi_event_emit(event, qdict);
     } else {
         QDict *data = qobject_to(QDict, qdict_get(qdict, "data"));
         MonitorQAPIEventState key = { .event = event, .data = data };

         evstate = g_hash_table_lookup(monitor_qapi_event_state, &key);
         assert(!evstate || timer_pending(evstate->timer));

         if (evstate) {
             /*
              * Timer is pending for (at least) evconf->rate ns after
              * last send.  Store event for sending when timer fires,
              * replacing a prior stored event if any.
              */
             qobject_unref(evstate->qdict);
             evstate->qdict = qobject_ref(qdict);
         } else {
             /*
              * Last send was (at least) evconf->rate ns ago.
              * Send immediately, and arm the timer to call
              * monitor_qapi_event_handler() in evconf->rate ns.  Any
              * events arriving before then will be delayed until then.
              */
             int64_t now = qemu_clock_get_ns(monitor_get_event_clock());

             monitor_qapi_event_emit(event, qdict);

             evstate = g_new(MonitorQAPIEventState, 1);
             evstate->event = event;
             evstate->data = qobject_ref(data);
             evstate->qdict = NULL;
             evstate->timer = timer_new_ns(monitor_get_event_clock(),
                                           monitor_qapi_event_handler,
                                           evstate);
             g_hash_table_add(monitor_qapi_event_state, evstate);
             timer_mod_ns(evstate->timer, now + evconf->rate);
         }
     }

     qemu_mutex_unlock(&monitor_lock);
 }

 void qapi_event_emit(QAPIEvent event, QDict *qdict)
 {
     /*
      * monitor_qapi_event_queue_no_reenter() is not reentrant: it
      * would deadlock on monitor_lock.  Work around by queueing
      * events in thread-local storage.
      * TODO: remove this, make it re-enter safe.
      */
     typedef struct MonitorQapiEvent {
         QAPIEvent event;
         QDict *qdict;
         QSIMPLEQ_ENTRY(MonitorQapiEvent) entry;
     } MonitorQapiEvent;
     static __thread QSIMPLEQ_HEAD(, MonitorQapiEvent) event_queue;
     static __thread bool reentered;
     MonitorQapiEvent *ev;

     if (!reentered) {
         QSIMPLEQ_INIT(&event_queue);
     }

     ev = g_new(MonitorQapiEvent, 1);
     ev->qdict = qobject_ref(qdict);
     ev->event = event;
     QSIMPLEQ_INSERT_TAIL(&event_queue, ev, entry);
     if (reentered) {
         return;
     }

     reentered = true;

     while ((ev = QSIMPLEQ_FIRST(&event_queue)) != NULL) {
         QSIMPLEQ_REMOVE_HEAD(&event_queue, entry);
         monitor_qapi_event_queue_no_reenter(ev->event, ev->qdict);
         qobject_unref(ev->qdict);
         g_free(ev);
     }

     reentered = false;
 }

 /*
  * This function runs evconf->rate ns after sending a throttled
  * event.
  * If another event has since been stored, send it.
  */
 static void monitor_qapi_event_handler(void *opaque)
 {
     MonitorQAPIEventState *evstate = opaque;
     MonitorQAPIEventConf *evconf = &monitor_qapi_event_conf[evstate->event];

     trace_monitor_protocol_event_handler(evstate->event, evstate->qdict);
     qemu_mutex_lock(&monitor_lock);

     if (evstate->qdict) {
         int64_t now = qemu_clock_get_ns(monitor_get_event_clock());

         monitor_qapi_event_emit(evstate->event, evstate->qdict);
         qobject_unref(evstate->qdict);
         evstate->qdict = NULL;
         timer_mod_ns(evstate->timer, now + evconf->rate);
     } else {
         g_hash_table_remove(monitor_qapi_event_state, evstate);
         qobject_unref(evstate->data);
         timer_free(evstate->timer);
         g_free(evstate);
     }

     qemu_mutex_unlock(&monitor_lock);
 }

 static unsigned int qapi_event_throttle_hash(const void *key)
 {
     const MonitorQAPIEventState *evstate = key;
     unsigned int hash = evstate->event * 255;

     if (evstate->event == QAPI_EVENT_VSERPORT_CHANGE) {
         hash += g_str_hash(qdict_get_str(evstate->data, "id"));
     }

     if (evstate->event == QAPI_EVENT_QUORUM_REPORT_BAD) {
         hash += g_str_hash(qdict_get_str(evstate->data, "node-name"));
     }

     return hash;
 }

 static gboolean qapi_event_throttle_equal(const void *a, const void *b)
 {
     const MonitorQAPIEventState *eva = a;
     const MonitorQAPIEventState *evb = b;

     if (eva->event != evb->event) {
         return FALSE;
     }

     if (eva->event == QAPI_EVENT_VSERPORT_CHANGE) {
         return !strcmp(qdict_get_str(eva->data, "id"),
                        qdict_get_str(evb->data, "id"));
     }

     if (eva->event == QAPI_EVENT_QUORUM_REPORT_BAD) {
         return !strcmp(qdict_get_str(eva->data, "node-name"),
                        qdict_get_str(evb->data, "node-name"));
     }

     return TRUE;
 }

 int monitor_suspend(Monitor *mon)
 {
     if (monitor_is_hmp_non_interactive(mon)) {
         return -ENOTTY;
     }

     atomic_inc(&mon->suspend_cnt);

     if (mon->use_io_thread) {
         /*
          * Kick I/O thread to make sure this takes effect.  It'll be
          * evaluated again in prepare() of the watch object.
          */
         aio_notify(iothread_get_aio_context(mon_iothread));
     }

     trace_monitor_suspend(mon, 1);
     return 0;
 }

 static void monitor_accept_input(void *opaque)
 {
     Monitor *mon = opaque;

     qemu_chr_fe_accept_input(&mon->chr);
 }

 void monitor_resume(Monitor *mon)
 {
     if (monitor_is_hmp_non_interactive(mon)) {
         return;
     }

     if (atomic_dec_fetch(&mon->suspend_cnt) == 0) {
         AioContext *ctx;

         if (mon->use_io_thread) {
             ctx = iothread_get_aio_context(mon_iothread);
         } else {
             ctx = qemu_get_aio_context();
         }

         if (!monitor_is_qmp(mon)) {
             MonitorHMP *hmp_mon = container_of(mon, MonitorHMP, common);
             assert(hmp_mon->rs);
             readline_show_prompt(hmp_mon->rs);
         }

         aio_bh_schedule_oneshot(ctx, monitor_accept_input, mon);
     }

     trace_monitor_suspend(mon, -1);
 }

 int monitor_can_read(void *opaque)
 {
     Monitor *mon = opaque;

     return !atomic_mb_read(&mon->suspend_cnt);
 }

 void monitor_list_append(Monitor *mon)
 {
     qemu_mutex_lock(&monitor_lock);
     /*
      * This prevents inserting new monitors during monitor_cleanup().
      * A cleaner solution would involve the main thread telling other
      * threads to terminate, waiting for their termination.
      */
     if (!monitor_destroyed) {
         QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
         mon = NULL;
     }
     qemu_mutex_unlock(&monitor_lock);

     if (mon) {
         monitor_data_destroy(mon);
         g_free(mon);
     }
 }

 static void monitor_iothread_init(void)
 {
     mon_iothread = iothread_create("mon_iothread", &error_abort);
 }

 void monitor_data_init(Monitor *mon, bool is_qmp, bool skip_flush,
                        bool use_io_thread)
 {
     if (use_io_thread && !mon_iothread) {
         monitor_iothread_init();
     }
     qemu_mutex_init(&mon->mon_lock);
     mon->is_qmp = is_qmp;
     mon->outbuf = qstring_new();
     mon->skip_flush = skip_flush;
     mon->use_io_thread = use_io_thread;
 }

 void monitor_data_destroy(Monitor *mon)
 {
     g_free(mon->mon_cpu_path);
     qemu_chr_fe_deinit(&mon->chr, false);
     if (monitor_is_qmp(mon)) {
         monitor_data_destroy_qmp(container_of(mon, MonitorQMP, common));
     } else {
         readline_free(container_of(mon, MonitorHMP, common)->rs);
     }
     qobject_unref(mon->outbuf);
     qemu_mutex_destroy(&mon->mon_lock);
 }

 void monitor_cleanup(void)
 {
     /*
      * We need to explicitly stop the I/O thread (but not destroy it),
      * clean up the monitor resources, then destroy the I/O thread since
      * we need to unregister from chardev below in
      * monitor_data_destroy(), and chardev is not thread-safe yet
      */
     if (mon_iothread) {
         iothread_stop(mon_iothread);
     }

     /* Flush output buffers and destroy monitors */
     qemu_mutex_lock(&monitor_lock);
     monitor_destroyed = true;
     while (!QTAILQ_EMPTY(&mon_list)) {
         Monitor *mon = QTAILQ_FIRST(&mon_list);
         QTAILQ_REMOVE(&mon_list, mon, entry);
         /* Permit QAPI event emission from character frontend release */
         qemu_mutex_unlock(&monitor_lock);
         monitor_flush(mon);
         monitor_data_destroy(mon);
         qemu_mutex_lock(&monitor_lock);
         g_free(mon);
     }
     qemu_mutex_unlock(&monitor_lock);

     /* QEMUBHs needs to be deleted before destroying the I/O thread */
     qemu_bh_delete(qmp_dispatcher_bh);
     qmp_dispatcher_bh = NULL;
     if (mon_iothread) {
         iothread_destroy(mon_iothread);
         mon_iothread = NULL;
     }
 }

 static void monitor_qapi_event_init(void)
 {
     monitor_qapi_event_state = g_hash_table_new(qapi_event_throttle_hash,
                                                 qapi_event_throttle_equal);
 }

 void monitor_init_globals_core(void)
 {
     monitor_qapi_event_init();
     qemu_mutex_init(&monitor_lock);

     /*
      * The dispatcher BH must run in the main loop thread, since we
      * have commands assuming that context.  It would be nice to get
      * rid of those assumptions.
      */
     qmp_dispatcher_bh = aio_bh_new(iohandler_get_aio_context(),
                                    monitor_qmp_bh_dispatcher,
                                    NULL);
 }

 int monitor_init(MonitorOptions *opts, bool allow_hmp, Error **errp)
 {
     Chardev *chr;
     Error *local_err = NULL;

     chr = qemu_chr_find(opts->chardev);
     if (chr == NULL) {
         error_setg(errp, "chardev \"%s\" not found", opts->chardev);
         return -1;
     }

     if (!opts->has_mode) {
         opts->mode = allow_hmp ? MONITOR_MODE_READLINE : MONITOR_MODE_CONTROL;
     }

     switch (opts->mode) {
     case MONITOR_MODE_CONTROL:
         monitor_init_qmp(chr, opts->pretty, &local_err);
         break;
     case MONITOR_MODE_READLINE:
         if (!allow_hmp) {
             error_setg(errp, "Only QMP is supported");
             return -1;
         }
         if (opts->pretty) {
             warn_report("'pretty' is deprecated for HMP monitors, it has no "
                         "effect and will be removed in future versions");
         }
         monitor_init_hmp(chr, true, &local_err);
         break;
     default:
         g_assert_not_reached();
     }

     if (local_err) {
         error_propagate(errp, local_err);
         return -1;
     }
     return 0;
 }

 int monitor_init_opts(QemuOpts *opts, Error **errp)
 {
     Visitor *v;
     MonitorOptions *options;
     Error *local_err = NULL;

     v = opts_visitor_new(opts);
     visit_type_MonitorOptions(v, NULL, &options, &local_err);
     visit_free(v);

     if (local_err) {
         goto out;
     }

     monitor_init(options, true, &local_err);
     qapi_free_MonitorOptions(options);

 out:
     if (local_err) {
         error_propagate(errp, local_err);
         return -1;
     }
     return 0;
 }

 QemuOptsList qemu_mon_opts = {
     .name = "mon",
     .implied_opt_name = "chardev",
     .head = QTAILQ_HEAD_INITIALIZER(qemu_mon_opts.head),
     .desc = {
         {
             .name = "mode",
             .type = QEMU_OPT_STRING,
         },{
             .name = "chardev",
             .type = QEMU_OPT_STRING,
         },{
             .name = "pretty",
             .type = QEMU_OPT_BOOL,
         },
         { /* end of list */ }
     },
 };
	/*
	* QEMU monitor
	*
	* Copyright (c) 2003-2004 Fabrice Bellard
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	* THE SOFTWARE.
	*/

	#include "qemu/osdep.h"
	#include "monitor-internal.h"
	#include "qapi/error.h"
	#include "qapi/opts-visitor.h"
	#include "qapi/qapi-emit-events.h"
	#include "qapi/qapi-visit-control.h"
	#include "qapi/qmp/qdict.h"
	#include "qapi/qmp/qstring.h"
	#include "qemu/error-report.h"
	#include "qemu/option.h"
	#include "sysemu/qtest.h"
	#include "sysemu/sysemu.h"
	#include "trace.h"

	/*
	* To prevent flooding clients, events can be throttled. The
	* throttling is calculated globally, rather than per-Monitor
	* instance.
	*/
	typedef struct MonitorQAPIEventState {
	QAPIEvent event; /* Throttling state for this event type and... */
	QDict data; / ... data, see qapi_event_throttle_equal() */
	QEMUTimer timer; / Timer for handling delayed events */
	QDict qdict; / Delayed event (if any) */
	} MonitorQAPIEventState;

	typedef struct {
	int64_t rate; /* Minimum time (in ns) between two events */
	} MonitorQAPIEventConf;

	/* Shared monitor I/O thread */
	IOThread *mon_iothread;

	/* Bottom half to dispatch the requests received from I/O thread */
	QEMUBH *qmp_dispatcher_bh;

	/* Protects mon_list, monitor_qapi_event_state, monitor_destroyed. */
	QemuMutex monitor_lock;
	static GHashTable *monitor_qapi_event_state;

	MonitorList mon_list;
	int mon_refcount;
	static bool monitor_destroyed;

	__thread Monitor *cur_mon;

	/**
	* Is the current monitor, if any, a QMP monitor?
	*/
	bool monitor_cur_is_qmp(void)
	{
	return cur_mon && monitor_is_qmp(cur_mon);
	}

	/**
	* Is @mon is using readline?
	* Note: not all HMP monitors use readline, e.g., gdbserver has a
	* non-interactive HMP monitor, so readline is not used there.
	*/
	static inline bool monitor_uses_readline(const MonitorHMP *mon)
	{
	return mon->use_readline;
	}

	static inline bool monitor_is_hmp_non_interactive(const Monitor *mon)
	{
	if (monitor_is_qmp(mon)) {
	return false;
	}

	return !monitor_uses_readline(container_of(mon, MonitorHMP, common));
	}

	static void monitor_flush_locked(Monitor *mon);

	static gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond,
	void *opaque)
	{
	Monitor *mon = opaque;

	qemu_mutex_lock(&mon->mon_lock);
	mon->out_watch = 0;
	monitor_flush_locked(mon);
	qemu_mutex_unlock(&mon->mon_lock);
	return FALSE;
	}

	/* Caller must hold mon->mon_lock */
	static void monitor_flush_locked(Monitor *mon)
	{
	int rc;
	size_t len;
	const char *buf;

	if (mon->skip_flush) {
	return;
	}

	buf = qstring_get_str(mon->outbuf);
	len = qstring_get_length(mon->outbuf);

	if (len && !mon->mux_out) {
	rc = qemu_chr_fe_write(&mon->chr, (const uint8_t *) buf, len);
	if ((rc < 0 && errno != EAGAIN) \|\| (rc == len)) {
	/* all flushed or error */
	qobject_unref(mon->outbuf);
	mon->outbuf = qstring_new();
	return;
	}
	if (rc > 0) {
	/* partial write */
	QString *tmp = qstring_from_str(buf + rc);
	qobject_unref(mon->outbuf);
	mon->outbuf = tmp;
	}
	if (mon->out_watch == 0) {
	mon->out_watch =
	qemu_chr_fe_add_watch(&mon->chr, G_IO_OUT \| G_IO_HUP,
	monitor_unblocked, mon);
	}
	}
	}

	void monitor_flush(Monitor *mon)
	{
	qemu_mutex_lock(&mon->mon_lock);
	monitor_flush_locked(mon);
	qemu_mutex_unlock(&mon->mon_lock);
	}

	/* flush at every end of line */
	int monitor_puts(Monitor mon, const char str)
	{
	int i;
	char c;

	qemu_mutex_lock(&mon->mon_lock);
	for (i = 0; str[i]; i++) {
	c = str[i];
	if (c == '\n') {
	qstring_append_chr(mon->outbuf, '\r');
	}
	qstring_append_chr(mon->outbuf, c);
	if (c == '\n') {
	monitor_flush_locked(mon);
	}
	}
	qemu_mutex_unlock(&mon->mon_lock);

	return i;
	}

	int monitor_vprintf(Monitor mon, const char fmt, va_list ap)
	{
	char *buf;
	int n;

	if (!mon) {
	return -1;
	}

	if (monitor_is_qmp(mon)) {
	return -1;
	}

	buf = g_strdup_vprintf(fmt, ap);
	n = monitor_puts(mon, buf);
	g_free(buf);
	return n;
	}

	int monitor_printf(Monitor mon, const char fmt, ...)
	{
	int ret;

	va_list ap;
	va_start(ap, fmt);
	ret = monitor_vprintf(mon, fmt, ap);
	va_end(ap);
	return ret;
	}

	/*
	* Print to current monitor if we have one, else to stderr.
	*/
	int error_vprintf(const char *fmt, va_list ap)
	{
	if (cur_mon && !monitor_cur_is_qmp()) {
	return monitor_vprintf(cur_mon, fmt, ap);
	}
	return vfprintf(stderr, fmt, ap);
	}

	int error_vprintf_unless_qmp(const char *fmt, va_list ap)
	{
	if (!cur_mon) {
	return vfprintf(stderr, fmt, ap);
	}
	if (!monitor_cur_is_qmp()) {
	return monitor_vprintf(cur_mon, fmt, ap);
	}
	return -1;
	}


	static MonitorQAPIEventConf monitor_qapi_event_conf[QAPI_EVENT__MAX] = {
	/* Limit guest-triggerable events to 1 per second */
	[QAPI_EVENT_RTC_CHANGE] = { 1000 * SCALE_MS },
	[QAPI_EVENT_WATCHDOG] = { 1000 * SCALE_MS },
	[QAPI_EVENT_BALLOON_CHANGE] = { 1000 * SCALE_MS },
	[QAPI_EVENT_QUORUM_REPORT_BAD] = { 1000 * SCALE_MS },
	[QAPI_EVENT_QUORUM_FAILURE] = { 1000 * SCALE_MS },
	[QAPI_EVENT_VSERPORT_CHANGE] = { 1000 * SCALE_MS },
	};

	/*
	* Return the clock to use for recording an event's time.
	* It's QEMU_CLOCK_REALTIME, except for qtests it's
	* QEMU_CLOCK_VIRTUAL, to support testing rate limits.
	* Beware: result is invalid before configure_accelerator().
	*/
	static inline QEMUClockType monitor_get_event_clock(void)
	{
	return qtest_enabled() ? QEMU_CLOCK_VIRTUAL : QEMU_CLOCK_REALTIME;
	}

	/*
	* Broadcast an event to all monitors.
	* @qdict is the event object. Its member "event" must match @event.
	* Caller must hold monitor_lock.
	*/
	static void monitor_qapi_event_emit(QAPIEvent event, QDict *qdict)
	{
	Monitor *mon;
	MonitorQMP *qmp_mon;

	trace_monitor_protocol_event_emit(event, qdict);
	QTAILQ_FOREACH(mon, &mon_list, entry) {
	if (!monitor_is_qmp(mon)) {
	continue;
	}

	qmp_mon = container_of(mon, MonitorQMP, common);
	if (qmp_mon->commands != &qmp_cap_negotiation_commands) {
	qmp_send_response(qmp_mon, qdict);
	}
	}
	}

	static void monitor_qapi_event_handler(void *opaque);

	/*
	* Queue a new event for emission to Monitor instances,
	* applying any rate limiting if required.
	*/
	static void
	monitor_qapi_event_queue_no_reenter(QAPIEvent event, QDict *qdict)
	{
	MonitorQAPIEventConf *evconf;
	MonitorQAPIEventState *evstate;

	assert(event < QAPI_EVENT__MAX);
	evconf = &monitor_qapi_event_conf[event];
	trace_monitor_protocol_event_queue(event, qdict, evconf->rate);

	qemu_mutex_lock(&monitor_lock);

	if (!evconf->rate) {
	/* Unthrottled event */
	monitor_qapi_event_emit(event, qdict);
	} else {
	QDict *data = qobject_to(QDict, qdict_get(qdict, "data"));
	MonitorQAPIEventState key = { .event = event, .data = data };

	evstate = g_hash_table_lookup(monitor_qapi_event_state, &key);
	assert(!evstate \|\| timer_pending(evstate->timer));

	if (evstate) {
	/*
	* Timer is pending for (at least) evconf->rate ns after
	* last send. Store event for sending when timer fires,
	* replacing a prior stored event if any.
	*/
	qobject_unref(evstate->qdict);
	evstate->qdict = qobject_ref(qdict);
	} else {
	/*
	* Last send was (at least) evconf->rate ns ago.
	* Send immediately, and arm the timer to call
	* monitor_qapi_event_handler() in evconf->rate ns. Any
	* events arriving before then will be delayed until then.
	*/
	int64_t now = qemu_clock_get_ns(monitor_get_event_clock());

	monitor_qapi_event_emit(event, qdict);

	evstate = g_new(MonitorQAPIEventState, 1);
	evstate->event = event;
	evstate->data = qobject_ref(data);
	evstate->qdict = NULL;
	evstate->timer = timer_new_ns(monitor_get_event_clock(),
	monitor_qapi_event_handler,
	evstate);
	g_hash_table_add(monitor_qapi_event_state, evstate);
	timer_mod_ns(evstate->timer, now + evconf->rate);
	}
	}

	qemu_mutex_unlock(&monitor_lock);
	}

	void qapi_event_emit(QAPIEvent event, QDict *qdict)
	{
	/*
	* monitor_qapi_event_queue_no_reenter() is not reentrant: it
	* would deadlock on monitor_lock. Work around by queueing
	* events in thread-local storage.
	* TODO: remove this, make it re-enter safe.
	*/
	typedef struct MonitorQapiEvent {
	QAPIEvent event;
	QDict *qdict;
	QSIMPLEQ_ENTRY(MonitorQapiEvent) entry;
	} MonitorQapiEvent;
	static __thread QSIMPLEQ_HEAD(, MonitorQapiEvent) event_queue;
	static __thread bool reentered;
	MonitorQapiEvent *ev;

	if (!reentered) {
	QSIMPLEQ_INIT(&event_queue);
	}

	ev = g_new(MonitorQapiEvent, 1);
	ev->qdict = qobject_ref(qdict);
	ev->event = event;
	QSIMPLEQ_INSERT_TAIL(&event_queue, ev, entry);
	if (reentered) {
	return;
	}

	reentered = true;

	while ((ev = QSIMPLEQ_FIRST(&event_queue)) != NULL) {
	QSIMPLEQ_REMOVE_HEAD(&event_queue, entry);
	monitor_qapi_event_queue_no_reenter(ev->event, ev->qdict);
	qobject_unref(ev->qdict);
	g_free(ev);
	}

	reentered = false;
	}

	/*
	* This function runs evconf->rate ns after sending a throttled
	* event.
	* If another event has since been stored, send it.
	*/
	static void monitor_qapi_event_handler(void *opaque)
	{
	MonitorQAPIEventState *evstate = opaque;
	MonitorQAPIEventConf *evconf = &monitor_qapi_event_conf[evstate->event];

	trace_monitor_protocol_event_handler(evstate->event, evstate->qdict);
	qemu_mutex_lock(&monitor_lock);

	if (evstate->qdict) {
	int64_t now = qemu_clock_get_ns(monitor_get_event_clock());

	monitor_qapi_event_emit(evstate->event, evstate->qdict);
	qobject_unref(evstate->qdict);
	evstate->qdict = NULL;
	timer_mod_ns(evstate->timer, now + evconf->rate);
	} else {
	g_hash_table_remove(monitor_qapi_event_state, evstate);
	qobject_unref(evstate->data);
	timer_free(evstate->timer);
	g_free(evstate);
	}

	qemu_mutex_unlock(&monitor_lock);
	}

	static unsigned int qapi_event_throttle_hash(const void *key)
	{
	const MonitorQAPIEventState *evstate = key;
	unsigned int hash = evstate->event * 255;

	if (evstate->event == QAPI_EVENT_VSERPORT_CHANGE) {
	hash += g_str_hash(qdict_get_str(evstate->data, "id"));
	}

	if (evstate->event == QAPI_EVENT_QUORUM_REPORT_BAD) {
	hash += g_str_hash(qdict_get_str(evstate->data, "node-name"));
	}

	return hash;
	}

	static gboolean qapi_event_throttle_equal(const void a, const void b)
	{
	const MonitorQAPIEventState *eva = a;
	const MonitorQAPIEventState *evb = b;

	if (eva->event != evb->event) {
	return FALSE;
	}

	if (eva->event == QAPI_EVENT_VSERPORT_CHANGE) {
	return !strcmp(qdict_get_str(eva->data, "id"),
	qdict_get_str(evb->data, "id"));
	}

	if (eva->event == QAPI_EVENT_QUORUM_REPORT_BAD) {
	return !strcmp(qdict_get_str(eva->data, "node-name"),
	qdict_get_str(evb->data, "node-name"));
	}

	return TRUE;
	}

	int monitor_suspend(Monitor *mon)
	{
	if (monitor_is_hmp_non_interactive(mon)) {
	return -ENOTTY;
	}

	atomic_inc(&mon->suspend_cnt);

	if (mon->use_io_thread) {
	/*
	* Kick I/O thread to make sure this takes effect. It'll be
	* evaluated again in prepare() of the watch object.
	*/
	aio_notify(iothread_get_aio_context(mon_iothread));
	}

	trace_monitor_suspend(mon, 1);
	return 0;
	}

	static void monitor_accept_input(void *opaque)
	{
	Monitor *mon = opaque;

	qemu_chr_fe_accept_input(&mon->chr);
	}

	void monitor_resume(Monitor *mon)
	{
	if (monitor_is_hmp_non_interactive(mon)) {
	return;
	}

	if (atomic_dec_fetch(&mon->suspend_cnt) == 0) {
	AioContext *ctx;

	if (mon->use_io_thread) {
	ctx = iothread_get_aio_context(mon_iothread);
	} else {
	ctx = qemu_get_aio_context();
	}

	if (!monitor_is_qmp(mon)) {
	MonitorHMP *hmp_mon = container_of(mon, MonitorHMP, common);
	assert(hmp_mon->rs);
	readline_show_prompt(hmp_mon->rs);
	}

	aio_bh_schedule_oneshot(ctx, monitor_accept_input, mon);
	}

	trace_monitor_suspend(mon, -1);
	}

	int monitor_can_read(void *opaque)
	{
	Monitor *mon = opaque;

	return !atomic_mb_read(&mon->suspend_cnt);
	}

	void monitor_list_append(Monitor *mon)
	{
	qemu_mutex_lock(&monitor_lock);
	/*
	* This prevents inserting new monitors during monitor_cleanup().
	* A cleaner solution would involve the main thread telling other
	* threads to terminate, waiting for their termination.
	*/
	if (!monitor_destroyed) {
	QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
	mon = NULL;
	}
	qemu_mutex_unlock(&monitor_lock);

	if (mon) {
	monitor_data_destroy(mon);
	g_free(mon);
	}
	}

	static void monitor_iothread_init(void)
	{
	mon_iothread = iothread_create("mon_iothread", &error_abort);
	}

	void monitor_data_init(Monitor *mon, bool is_qmp, bool skip_flush,
	bool use_io_thread)
	{
	if (use_io_thread && !mon_iothread) {
	monitor_iothread_init();
	}
	qemu_mutex_init(&mon->mon_lock);
	mon->is_qmp = is_qmp;
	mon->outbuf = qstring_new();
	mon->skip_flush = skip_flush;
	mon->use_io_thread = use_io_thread;
	}

	void monitor_data_destroy(Monitor *mon)
	{
	g_free(mon->mon_cpu_path);
	qemu_chr_fe_deinit(&mon->chr, false);
	if (monitor_is_qmp(mon)) {
	monitor_data_destroy_qmp(container_of(mon, MonitorQMP, common));
	} else {
	readline_free(container_of(mon, MonitorHMP, common)->rs);
	}
	qobject_unref(mon->outbuf);
	qemu_mutex_destroy(&mon->mon_lock);
	}

	void monitor_cleanup(void)
	{
	/*
	* We need to explicitly stop the I/O thread (but not destroy it),
	* clean up the monitor resources, then destroy the I/O thread since
	* we need to unregister from chardev below in
	* monitor_data_destroy(), and chardev is not thread-safe yet
	*/
	if (mon_iothread) {
	iothread_stop(mon_iothread);
	}

	/* Flush output buffers and destroy monitors */
	qemu_mutex_lock(&monitor_lock);
	monitor_destroyed = true;
	while (!QTAILQ_EMPTY(&mon_list)) {
	Monitor *mon = QTAILQ_FIRST(&mon_list);
	QTAILQ_REMOVE(&mon_list, mon, entry);
	/* Permit QAPI event emission from character frontend release */
	qemu_mutex_unlock(&monitor_lock);
	monitor_flush(mon);
	monitor_data_destroy(mon);
	qemu_mutex_lock(&monitor_lock);
	g_free(mon);
	}
	qemu_mutex_unlock(&monitor_lock);

	/* QEMUBHs needs to be deleted before destroying the I/O thread */
	qemu_bh_delete(qmp_dispatcher_bh);
	qmp_dispatcher_bh = NULL;
	if (mon_iothread) {
	iothread_destroy(mon_iothread);
	mon_iothread = NULL;
	}
	}

	static void monitor_qapi_event_init(void)
	{
	monitor_qapi_event_state = g_hash_table_new(qapi_event_throttle_hash,
	qapi_event_throttle_equal);
	}

	void monitor_init_globals_core(void)
	{
	monitor_qapi_event_init();
	qemu_mutex_init(&monitor_lock);

	/*
	* The dispatcher BH must run in the main loop thread, since we
	* have commands assuming that context. It would be nice to get
	* rid of those assumptions.
	*/
	qmp_dispatcher_bh = aio_bh_new(iohandler_get_aio_context(),
	monitor_qmp_bh_dispatcher,
	NULL);
	}

	int monitor_init(MonitorOptions opts, bool allow_hmp, Error *errp)
	{
	Chardev *chr;
	Error *local_err = NULL;

	chr = qemu_chr_find(opts->chardev);
	if (chr == NULL) {
	error_setg(errp, "chardev \"%s\" not found", opts->chardev);
	return -1;
	}

	if (!opts->has_mode) {
	opts->mode = allow_hmp ? MONITOR_MODE_READLINE : MONITOR_MODE_CONTROL;
	}

	switch (opts->mode) {
	case MONITOR_MODE_CONTROL:
	monitor_init_qmp(chr, opts->pretty, &local_err);
	break;
	case MONITOR_MODE_READLINE:
	if (!allow_hmp) {
	error_setg(errp, "Only QMP is supported");
	return -1;
	}
	if (opts->pretty) {
	warn_report("'pretty' is deprecated for HMP monitors, it has no "
	"effect and will be removed in future versions");
	}
	monitor_init_hmp(chr, true, &local_err);
	break;
	default:
	g_assert_not_reached();
	}

	if (local_err) {
	error_propagate(errp, local_err);
	return -1;
	}
	return 0;
	}

	int monitor_init_opts(QemuOpts opts, Error *errp)
	{
	Visitor *v;
	MonitorOptions *options;
	Error *local_err = NULL;

	v = opts_visitor_new(opts);
	visit_type_MonitorOptions(v, NULL, &options, &local_err);
	visit_free(v);

	if (local_err) {
	goto out;
	}

	monitor_init(options, true, &local_err);
	qapi_free_MonitorOptions(options);

	out:
	if (local_err) {
	error_propagate(errp, local_err);
	return -1;
	}
	return 0;
	}

	QemuOptsList qemu_mon_opts = {
	.name = "mon",
	.implied_opt_name = "chardev",
	.head = QTAILQ_HEAD_INITIALIZER(qemu_mon_opts.head),
	.desc = {
	{
	.name = "mode",
	.type = QEMU_OPT_STRING,
	},{
	.name = "chardev",
	.type = QEMU_OPT_STRING,
	},{
	.name = "pretty",
	.type = QEMU_OPT_BOOL,
	},
	{ /* end of list */ }
	},
	};