diff options
| -rw-r--r-- | docs/interop/qmp-spec.txt | 5 | ||||
| -rw-r--r-- | include/monitor/monitor.h | 2 | ||||
| -rw-r--r-- | monitor.c | 52 | ||||
| -rw-r--r-- | qapi/misc.json | 40 |
4 files changed, 28 insertions, 71 deletions
diff --git a/docs/interop/qmp-spec.txt b/docs/interop/qmp-spec.txt index 8f7da0245d..67e44a8120 100644 --- a/docs/interop/qmp-spec.txt +++ b/docs/interop/qmp-spec.txt @@ -130,8 +130,9 @@ to pass "id" with out-of-band commands. Passing it with all commands is recommended for clients that accept capability "oob". If the client sends in-band commands faster than the server can -execute them, the server will eventually drop commands to limit the -queue length. The sever sends event COMMAND_DROPPED then. +execute them, the server will stop reading the requests from the QMP +channel until the request queue length is reduced to an acceptable +range. Only a few commands support out-of-band execution. The ones that do have "allow-oob": true in output of query-qmp-schema. diff --git a/include/monitor/monitor.h b/include/monitor/monitor.h index 6fd2c53b09..0c0a37d8cb 100644 --- a/include/monitor/monitor.h +++ b/include/monitor/monitor.h @@ -15,6 +15,8 @@ extern __thread Monitor *cur_mon; #define MONITOR_USE_PRETTY 0x08 #define MONITOR_USE_OOB 0x10 +#define QMP_REQ_QUEUE_LEN_MAX 8 + bool monitor_cur_is_qmp(void); void monitor_init_globals(void); diff --git a/monitor.c b/monitor.c index 5ce2c58b76..d2529260ed 100644 --- a/monitor.c +++ b/monitor.c @@ -4110,8 +4110,12 @@ static void monitor_qmp_dispatch(Monitor *mon, QObject *req, QObject *id) * processing commands only on a very busy monitor. To achieve that, * when we process one request on a specific monitor, we put that * monitor to the end of mon_list queue. + * + * Note: if the function returned with non-NULL, then the caller will + * be with mon->qmp.qmp_queue_lock held, and the caller is responsible + * to release it. */ -static QMPRequest *monitor_qmp_requests_pop_any(void) +static QMPRequest *monitor_qmp_requests_pop_any_with_lock(void) { QMPRequest *req_obj = NULL; Monitor *mon; @@ -4121,10 +4125,11 @@ static QMPRequest *monitor_qmp_requests_pop_any(void) 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) { + /* With the lock of corresponding queue held */ break; } + qemu_mutex_unlock(&mon->qmp.qmp_queue_lock); } if (req_obj) { @@ -4143,30 +4148,34 @@ static QMPRequest *monitor_qmp_requests_pop_any(void) static void monitor_qmp_bh_dispatcher(void *data) { - QMPRequest *req_obj = monitor_qmp_requests_pop_any(); + QMPRequest *req_obj = monitor_qmp_requests_pop_any_with_lock(); QDict *rsp; bool need_resume; + Monitor *mon; if (!req_obj) { return; } + mon = req_obj->mon; /* qmp_oob_enabled() might change after "qmp_capabilities" */ - need_resume = !qmp_oob_enabled(req_obj->mon); + need_resume = !qmp_oob_enabled(mon) || + mon->qmp.qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1; + qemu_mutex_unlock(&mon->qmp.qmp_queue_lock); if (req_obj->req) { trace_monitor_qmp_cmd_in_band(qobject_get_try_str(req_obj->id) ?: ""); - monitor_qmp_dispatch(req_obj->mon, req_obj->req, req_obj->id); + monitor_qmp_dispatch(mon, req_obj->req, req_obj->id); } else { assert(req_obj->err); rsp = qmp_error_response(req_obj->err); req_obj->err = NULL; - monitor_qmp_respond(req_obj->mon, rsp, NULL); + monitor_qmp_respond(mon, rsp, NULL); qobject_unref(rsp); } if (need_resume) { /* Pairs with the monitor_suspend() in handle_qmp_command() */ - monitor_resume(req_obj->mon); + monitor_resume(mon); } qmp_request_free(req_obj); @@ -4174,8 +4183,6 @@ static void monitor_qmp_bh_dispatcher(void *data) qemu_bh_schedule(qmp_dispatcher_bh); } -#define QMP_REQ_QUEUE_LEN_MAX (8) - static void handle_qmp_command(void *opaque, QObject *req, Error *err) { Monitor *mon = opaque; @@ -4217,28 +4224,14 @@ static void handle_qmp_command(void *opaque, QObject *req, Error *err) qemu_mutex_lock(&mon->qmp.qmp_queue_lock); /* - * If OOB is not enabled on the current monitor, we'll emulate the - * old behavior that we won't process the current monitor any more - * until it has responded. This helps make sure that as long as - * OOB is not enabled, the server will never drop any command. + * Suspend the monitor when we can't queue more requests after + * this one. Dequeuing in monitor_qmp_bh_dispatcher() will resume + * it. Note that when OOB is disabled, we queue at most one + * command, for backward compatibility. */ - if (!qmp_oob_enabled(mon)) { + if (!qmp_oob_enabled(mon) || + mon->qmp.qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1) { monitor_suspend(mon); - } else { - /* Drop the request if queue is full. */ - if (mon->qmp.qmp_requests->length >= QMP_REQ_QUEUE_LEN_MAX) { - qemu_mutex_unlock(&mon->qmp.qmp_queue_lock); - /* - * FIXME @id's scope is just @mon, and broadcasting it is - * wrong. If another monitor's client has a command with - * the same ID in flight, the event will incorrectly claim - * that command was dropped. - */ - qapi_event_send_command_dropped(id, - COMMAND_DROP_REASON_QUEUE_FULL); - qmp_request_free(req_obj); - return; - } } /* @@ -4246,6 +4239,7 @@ static void handle_qmp_command(void *opaque, QObject *req, Error *err) * handled in time order. Ownership for req_obj, req, id, * etc. will be delivered to the handler side. */ + assert(mon->qmp.qmp_requests->length < QMP_REQ_QUEUE_LEN_MAX); g_queue_push_tail(mon->qmp.qmp_requests, req_obj); qemu_mutex_unlock(&mon->qmp.qmp_queue_lock); diff --git a/qapi/misc.json b/qapi/misc.json index 45121492dd..4211a732f3 100644 --- a/qapi/misc.json +++ b/qapi/misc.json @@ -3445,46 +3445,6 @@ { 'command': 'query-sev-capabilities', 'returns': 'SevCapability' } ## -# @CommandDropReason: -# -# Reasons that caused one command to be dropped. -# -# @queue-full: the command queue is full. This can only occur when -# the client sends a new non-oob command before the -# response to the previous non-oob command has been -# received. -# -# Since: 2.12 -## -{ 'enum': 'CommandDropReason', - 'data': [ 'queue-full' ] } - -## -# @COMMAND_DROPPED: -# -# Emitted when a command is dropped due to some reason. Commands can -# only be dropped when the oob capability is enabled. -# -# @id: The dropped command's "id" field. -# FIXME Broken by design. Events are broadcast to all monitors. If -# another monitor's client has a command with the same ID in flight, -# the event will incorrectly claim that command was dropped. -# -# @reason: The reason why the command is dropped. -# -# Since: 2.12 -# -# Example: -# -# { "event": "COMMAND_DROPPED", -# "data": {"result": {"id": "libvirt-102", -# "reason": "queue-full" } } } -# -## -{ 'event': 'COMMAND_DROPPED' , - 'data': { 'id': 'any', 'reason': 'CommandDropReason' } } - -## # @set-numa-node: # # Runtime equivalent of '-numa' CLI option, available at |