Originally QMP goes throw these steps:
JSON Parser --> QMP Dispatcher --> Respond
/|\ (2) (3) |
(1) | \|/ (4)
+--------- main thread --------+
This patch does this:
JSON Parser QMP Dispatcher --> Respond
/|\ | /|\ (4) |
| | (2) | (3) | (5)
(1) | +-----> | \|/
+--------- main thread <-------+
So the parsing job and the dispatching job is isolated now. It gives us
a chance in following up patches to totally move the parser outside.
The isloation is done using one QEMUBH. Only one dispatcher QEMUBH is
used for all the monitors.
Signed-off-by: Peter Xu <pet...@redhat.com>
---
monitor.c | 179 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 157 insertions(+), 22 deletions(-)
diff --git a/monitor.c b/monitor.c
index 47e969244d..e327ae115b 100644
--- a/monitor.c
+++ b/monitor.c
@@ -168,6 +168,10 @@ typedef struct {
*/
QmpCommandList *commands;
bool qmp_caps[QMP_CAPABILITY__MAX];
+ /* Protects qmp request/response queue. */
+ QemuMutex qmp_queue_lock;
+ /* Input queue that holds all the parsed QMP requests */
+ GQueue *qmp_requests;
} MonitorQMP;
/*
@@ -213,6 +217,8 @@ struct Monitor {
struct MonitorGlobal {
IOThread *mon_iothread;
+ /* Bottom half to dispatch the requests received from IO thread */
+ QEMUBH *qmp_dispatcher_bh;
};
static struct MonitorGlobal mon_global;
@@ -582,11 +588,13 @@ static void monitor_data_init(Monitor *mon, bool
skip_flush,
{
memset(mon, 0, sizeof(Monitor));
qemu_mutex_init(&mon->out_lock);
+ qemu_mutex_init(&mon->qmp.qmp_queue_lock);
mon->outbuf = qstring_new();
/* Use *mon_cmds by default. */
mon->cmd_table = mon_cmds;
mon->skip_flush = skip_flush;
mon->use_io_thr = use_io_thr;
+ mon->qmp.qmp_requests = g_queue_new();
}
static void monitor_data_destroy(Monitor *mon)
@@ -599,6 +607,8 @@ static void monitor_data_destroy(Monitor *mon)
g_free(mon->rs);
QDECREF(mon->outbuf);
qemu_mutex_destroy(&mon->out_lock);
+ qemu_mutex_destroy(&mon->qmp.qmp_queue_lock);
+ g_queue_free(mon->qmp.qmp_requests);
}
char *qmp_human_monitor_command(const char *command_line, bool has_cpu_index,
@@ -3907,29 +3917,31 @@ static void monitor_qmp_respond(Monitor *mon, QObject
*rsp,
qobject_decref(rsp);
}
-static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens,
- void *opaque)
+struct QMPRequest {
+ /* Owner of the request */
+ Monitor *mon;
+ /* "id" field of the request */
+ QObject *id;
+ /* Request object to be handled */
+ QObject *req;
+};
+typedef struct QMPRequest QMPRequest;
+
+/*
+ * Dispatch one single QMP request. The function will free the req_obj
+ * and objects inside it before return.
+ */
+static void monitor_qmp_dispatch_one(QMPRequest *req_obj)
{
- QObject *req, *rsp = NULL, *id = NULL;
+ Monitor *mon, *old_mon;
+ QObject *req, *rsp = NULL, *id;
QDict *qdict = NULL;
- Monitor *mon = opaque, *old_mon;
- Error *err = NULL;
- req = json_parser_parse_err(tokens, NULL, &err);
- if (!req && !err) {
- /* json_parser_parse_err() sucks: can fail without setting @err */
- error_setg(&err, QERR_JSON_PARSING);
- }
- if (err) {
- goto err_out;
- }
+ req = req_obj->req;
+ mon = req_obj->mon;
+ id = req_obj->id;
- qdict = qobject_to_qdict(req);
- if (qdict) {
- id = qdict_get(qdict, "id");
- qobject_incref(id);
- qdict_del(qdict, "id");
- } /* else will fail qmp_dispatch() */
+ g_free(req_obj);
if (trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
QString *req_json = qobject_to_json(req);
@@ -3940,7 +3952,7 @@ static void handle_qmp_command(JSONMessageParser *parser,
GQueue *tokens,
old_mon = cur_mon;
cur_mon = mon;
- rsp = qmp_dispatch(cur_mon->qmp.commands, req);
+ rsp = qmp_dispatch(mon->qmp.commands, req);
cur_mon = old_mon;
@@ -3956,12 +3968,122 @@ static void handle_qmp_command(JSONMessageParser
*parser, GQueue *tokens,
}
}
-err_out:
- monitor_qmp_respond(mon, rsp, err, id);
+ /* Respond if necessary */
+ monitor_qmp_respond(mon, rsp, NULL, id);
+
+ /* This pairs with the monitor_suspend() in handle_qmp_command(). */
+ if (!qmp_oob_enabled(mon)) {
+ monitor_resume(mon);
+ }
qobject_decref(req);
}
+/*
+ * Pop one QMP request from monitor queues, return NULL if not found.
+ * We are using round-robin fasion to pop the request, to avoid
+ * processing command only on a very busy monitor. To achieve that,
+ * when we processed one request on specific monitor, we put that
+ * monitor to the end of mon_list queue.
+ */
+static QMPRequest *monitor_qmp_requests_pop_one(void)
+{
+ QMPRequest *req_obj = NULL;
+ Monitor *mon;
+
+ qemu_mutex_lock(&monitor_lock);
+
+ QTAILQ_FOREACH(mon, &mon_list, entry) {
+ qemu_mutex_lock(&mon->qmp.qmp_queue_lock);
+ req_obj = g_queue_pop_head(mon->qmp.qmp_requests);
+ qemu_mutex_unlock(&mon->qmp.qmp_queue_lock);
+ if (req_obj) {
+ break;
+ }
+ }
+
+ if (req_obj) {
+ /*
+ * We found one request on the monitor. Degrade this monitor's
+ * priority to lowest by re-inserting it to end of queue.
+ */
+ QTAILQ_REMOVE(&mon_list, mon, entry);
+ QTAILQ_INSERT_TAIL(&mon_list, mon, entry);
+ }
+
+ qemu_mutex_unlock(&monitor_lock);
+
+ return req_obj;
+}
+
+static void monitor_qmp_bh_dispatcher(void *data)
+{
+ QMPRequest *req_obj;
+
+ while (true) {
+ req_obj = monitor_qmp_requests_pop_one();
+ if (!req_obj) {
+ break;
+ }
+ monitor_qmp_dispatch_one(req_obj);
+ }
+}
+
+static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens,
+ void *opaque)
+{
+ QObject *req, *id = NULL;
+ QDict *qdict = NULL;
+ Monitor *mon = opaque;
+ Error *err = NULL;
+ QMPRequest *req_obj;
+
+ req = json_parser_parse_err(tokens, NULL, &err);
+ if (!req && !err) {
+ /* json_parser_parse_err() sucks: can fail without setting @err */
+ error_setg(&err, QERR_JSON_PARSING);
+ }
+ if (err) {
+ monitor_qmp_respond(mon, NULL, err, NULL);
+ qobject_decref(req);
+ return;
+ }
+
+ qdict = qobject_to_qdict(req);
+ if (qdict) {
+ id = qdict_get(qdict, "id");
+ qobject_incref(id);
+ qdict_del(qdict, "id");
+ } /* else will fail qmp_dispatch() */
+
+ req_obj = g_new0(QMPRequest, 1);
+ req_obj->mon = mon;
+ req_obj->id = id;
+ req_obj->req = req;
+
+ /*
+ * Put the request to the end of queue so that requests will be
+ * handled in time order. Ownership for req_obj, req, id,
+ * etc. will be delivered to the handler side.
+ */
+ qemu_mutex_lock(&mon->qmp.qmp_queue_lock);
+ g_queue_push_tail(mon->qmp.qmp_requests, req_obj);
+ qemu_mutex_unlock(&mon->qmp.qmp_queue_lock);
+
+ /* Kick the dispatcher routine */
+ qemu_bh_schedule(mon_global.qmp_dispatcher_bh);
+
+ /*
+ * If OOB is not enabled on current monitor, we'll emulate the old
+ * behavior that we won't process current monitor any more until
+ * it is responded. This helps make sure that as long as OOB is
+ * not enabled, the server will never drop any command.
+ */
+ if (!qmp_oob_enabled(mon)) {
+ monitor_suspend(mon);
+ }
+}
+
static void monitor_qmp_read(void *opaque, const uint8_t *buf, int size)
{
Monitor *mon = opaque;
@@ -4148,6 +4270,15 @@ static void monitor_iothread_init(void)
* fetch the context we'll have that initialized.
*/
monitor_io_context_get();
+
+ /*
+ * This MUST be on main loop thread since we have commands that
+ * have assumption to be run on main loop thread (Yeah, we'd
+ * better remove this assumption in the future).
+ */
+ mon_global.qmp_dispatcher_bh = aio_bh_new(qemu_get_aio_context(),
+ monitor_qmp_bh_dispatcher,
+ NULL);
}
void monitor_init_globals(void)
@@ -4268,6 +4399,10 @@ void monitor_cleanup(void)
}
qemu_mutex_unlock(&monitor_lock);
+ /* QEMUBHs needs to be deleted before destroying the IOThread. */
+ qemu_bh_delete(mon_global.qmp_dispatcher_bh);
+ mon_global.qmp_dispatcher_bh = NULL;
+
iothread_destroy(mon_global.mon_iothread);
mon_global.mon_iothread = NULL;
}
--
2.13.5
