This moves the QMP dispatcher to a coroutine and runs all QMP command handlers that declare 'coroutine': true in coroutine context so they can avoid blocking the main loop while doing I/O or waiting for other events.
For commands that are not declared safe to run in a coroutine, the dispatcher drops out of coroutine context by calling the QMP command handler from a bottom half. Signed-off-by: Kevin Wolf <kw...@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com> --- include/qapi/qmp/dispatch.h | 2 + monitor/monitor-internal.h | 5 ++- monitor/monitor.c | 24 +++++++---- monitor/qmp.c | 83 +++++++++++++++++++++++-------------- qapi/qmp-dispatch.c | 38 ++++++++++++++++- 5 files changed, 111 insertions(+), 41 deletions(-) diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h index d6ce9efc8e..d6d5443391 100644 --- a/include/qapi/qmp/dispatch.h +++ b/include/qapi/qmp/dispatch.h @@ -30,6 +30,8 @@ typedef enum QmpCommandOptions typedef struct QmpCommand { const char *name; + /* Runs in coroutine context if QCO_COROUTINE is set, except for OOB + * commands */ QmpCommandFunc *fn; QmpCommandOptions options; QTAILQ_ENTRY(QmpCommand) node; diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h index d78f5ca190..7389b6a56c 100644 --- a/monitor/monitor-internal.h +++ b/monitor/monitor-internal.h @@ -154,7 +154,8 @@ static inline bool monitor_is_qmp(const Monitor *mon) typedef QTAILQ_HEAD(MonitorList, Monitor) MonitorList; extern IOThread *mon_iothread; -extern QEMUBH *qmp_dispatcher_bh; +extern Coroutine *qmp_dispatcher_co; +extern bool qmp_dispatcher_co_busy; extern QmpCommandList qmp_commands, qmp_cap_negotiation_commands; extern QemuMutex monitor_lock; extern MonitorList mon_list; @@ -172,7 +173,7 @@ void monitor_fdsets_cleanup(void); void qmp_send_response(MonitorQMP *mon, const QDict *rsp); void monitor_data_destroy_qmp(MonitorQMP *mon); -void monitor_qmp_bh_dispatcher(void *data); +void coroutine_fn monitor_qmp_dispatcher_co(void *data); int get_monitor_def(int64_t *pval, const char *name); void help_cmd(Monitor *mon, const char *name); diff --git a/monitor/monitor.c b/monitor/monitor.c index 12898b6448..c72763fa4e 100644 --- a/monitor/monitor.c +++ b/monitor/monitor.c @@ -53,8 +53,9 @@ typedef struct { /* Shared monitor I/O thread */ IOThread *mon_iothread; -/* Bottom half to dispatch the requests received from I/O thread */ -QEMUBH *qmp_dispatcher_bh; +/* Coroutine to dispatch the requests received from I/O thread */ +Coroutine *qmp_dispatcher_co; +bool qmp_dispatcher_co_busy; /* Protects mon_list, monitor_qapi_event_state, monitor_destroyed. */ QemuMutex monitor_lock; @@ -579,9 +580,16 @@ void monitor_cleanup(void) } 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; + /* The dispatcher needs to stop before destroying the I/O thread */ + if (!atomic_mb_read(&qmp_dispatcher_co_busy)) { + aio_co_schedule(iohandler_get_aio_context(), qmp_dispatcher_co); + qmp_dispatcher_co = NULL; + } + + AIO_WAIT_WHILE(qemu_get_aio_context(), + (aio_bh_poll(iohandler_get_aio_context()), + atomic_mb_read(&qmp_dispatcher_co_busy))); + if (mon_iothread) { iothread_destroy(mon_iothread); mon_iothread = NULL; @@ -604,9 +612,9 @@ void monitor_init_globals_core(void) * 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); + qmp_dispatcher_co = qemu_coroutine_create(monitor_qmp_dispatcher_co, NULL); + atomic_mb_set(&qmp_dispatcher_co_busy, true); + aio_co_schedule(iohandler_get_aio_context(), qmp_dispatcher_co); } QemuOptsList qemu_mon_opts = { diff --git a/monitor/qmp.c b/monitor/qmp.c index b67a8e7d1f..9fd66c7b97 100644 --- a/monitor/qmp.c +++ b/monitor/qmp.c @@ -133,6 +133,8 @@ static void monitor_qmp_respond(MonitorQMP *mon, QDict *rsp) } } +/* Runs outside of coroutine context for OOB commands, but in coroutine context + * for everything else. */ static void monitor_qmp_dispatch(MonitorQMP *mon, QObject *req) { Monitor *old_mon; @@ -211,43 +213,62 @@ static QMPRequest *monitor_qmp_requests_pop_any_with_lock(void) return req_obj; } -void monitor_qmp_bh_dispatcher(void *data) +void coroutine_fn monitor_qmp_dispatcher_co(void *data) { - QMPRequest *req_obj = monitor_qmp_requests_pop_any_with_lock(); + QMPRequest *req_obj = NULL; QDict *rsp; bool need_resume; MonitorQMP *mon; - if (!req_obj) { - return; - } + while (true) { + assert(atomic_mb_read(&qmp_dispatcher_co_busy) == true); + + while (!(req_obj = monitor_qmp_requests_pop_any_with_lock())) { + /* Wait to be reentered from handle_qmp_command, or terminate if + * qmp_dispatcher_co has been reset to NULL */ + atomic_mb_set(&qmp_dispatcher_co_busy, false); + if (qmp_dispatcher_co) { + qemu_coroutine_yield(); + } + /* qmp_dispatcher_co may have changed if we yielded and were + * reentered from monitor_cleanup() */ + if (!qmp_dispatcher_co) { + return; + } + atomic_mb_set(&qmp_dispatcher_co_busy, true); + } - mon = req_obj->mon; - /* qmp_oob_enabled() might change after "qmp_capabilities" */ - need_resume = !qmp_oob_enabled(mon) || - mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1; - qemu_mutex_unlock(&mon->qmp_queue_lock); - if (req_obj->req) { - QDict *qdict = qobject_to(QDict, req_obj->req); - QObject *id = qdict ? qdict_get(qdict, "id") : NULL; - trace_monitor_qmp_cmd_in_band(qobject_get_try_str(id) ?: ""); - monitor_qmp_dispatch(mon, req_obj->req); - } else { - assert(req_obj->err); - rsp = qmp_error_response(req_obj->err); - req_obj->err = NULL; - monitor_qmp_respond(mon, rsp); - qobject_unref(rsp); - } + aio_co_schedule(qemu_get_aio_context(), qmp_dispatcher_co); + qemu_coroutine_yield(); + + mon = req_obj->mon; + /* qmp_oob_enabled() might change after "qmp_capabilities" */ + need_resume = !qmp_oob_enabled(mon) || + mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1; + qemu_mutex_unlock(&mon->qmp_queue_lock); + if (req_obj->req) { + QDict *qdict = qobject_to(QDict, req_obj->req); + QObject *id = qdict ? qdict_get(qdict, "id") : NULL; + trace_monitor_qmp_cmd_in_band(qobject_get_try_str(id) ?: ""); + monitor_qmp_dispatch(mon, req_obj->req); + } else { + assert(req_obj->err); + rsp = qmp_error_response(req_obj->err); + req_obj->err = NULL; + monitor_qmp_respond(mon, rsp); + qobject_unref(rsp); + } - if (need_resume) { - /* Pairs with the monitor_suspend() in handle_qmp_command() */ - monitor_resume(&mon->common); - } - qmp_request_free(req_obj); + if (need_resume) { + /* Pairs with the monitor_suspend() in handle_qmp_command() */ + monitor_resume(&mon->common); + } + qmp_request_free(req_obj); - /* Reschedule instead of looping so the main loop stays responsive */ - qemu_bh_schedule(qmp_dispatcher_bh); + /* Reschedule instead of looping so the main loop stays responsive */ + aio_co_schedule(iohandler_get_aio_context(), qmp_dispatcher_co); + qemu_coroutine_yield(); + } } static void handle_qmp_command(void *opaque, QObject *req, Error *err) @@ -308,7 +329,9 @@ static void handle_qmp_command(void *opaque, QObject *req, Error *err) qemu_mutex_unlock(&mon->qmp_queue_lock); /* Kick the dispatcher routine */ - qemu_bh_schedule(qmp_dispatcher_bh); + if (!atomic_mb_read(&qmp_dispatcher_co_busy)) { + aio_co_wake(qmp_dispatcher_co); + } } static void monitor_qmp_read(void *opaque, const uint8_t *buf, int size) diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c index bc264b3c9b..6ccf19f2a2 100644 --- a/qapi/qmp-dispatch.c +++ b/qapi/qmp-dispatch.c @@ -12,6 +12,8 @@ */ #include "qemu/osdep.h" + +#include "monitor/monitor-internal.h" #include "qapi/error.h" #include "qapi/qmp/dispatch.h" #include "qapi/qmp/qdict.h" @@ -75,6 +77,23 @@ static QDict *qmp_dispatch_check_obj(const QObject *request, bool allow_oob, return dict; } +typedef struct QmpDispatchBH { + QmpCommand *cmd; + QDict *args; + QObject **ret; + Error **errp; + Coroutine *co; +} QmpDispatchBH; + +static void do_qmp_dispatch_bh(void *opaque) +{ + QmpDispatchBH *data = opaque; + data->cmd->fn(data->args, data->ret, data->errp); + aio_co_wake(data->co); +} + +/* Runs outside of coroutine context for OOB commands, but in coroutine context + * for everything else. */ static QObject *do_qmp_dispatch(QmpCommandList *cmds, QObject *request, bool allow_oob, Error **errp) { @@ -129,7 +148,22 @@ static QObject *do_qmp_dispatch(QmpCommandList *cmds, QObject *request, qobject_ref(args); } - cmd->fn(args, &ret, &local_err); + assert(!(oob && qemu_in_coroutine())); + if ((cmd->options & QCO_COROUTINE) || !qemu_in_coroutine()) { + cmd->fn(args, &ret, &local_err); + } else { + /* Must drop out of coroutine context for this one */ + QmpDispatchBH data = { + .cmd = cmd, + .args = args, + .ret = &ret, + .errp = &local_err, + .co = qemu_coroutine_self(), + }; + aio_bh_schedule_oneshot(qemu_get_aio_context(), do_qmp_dispatch_bh, + &data); + qemu_coroutine_yield(); + } if (local_err) { error_propagate(errp, local_err); } else if (cmd->options & QCO_NO_SUCCESS_RESP) { @@ -164,6 +198,8 @@ bool qmp_is_oob(const QDict *dict) && !qdict_haskey(dict, "execute"); } +/* Runs outside of coroutine context for OOB commands, but in coroutine context + * for everything else. */ QDict *qmp_dispatch(QmpCommandList *cmds, QObject *request, bool allow_oob) { -- 2.20.1