diff options
| -rw-r--r-- | include/qapi/qmp/dispatch.h | 1 | ||||
| -rw-r--r-- | monitor/monitor-internal.h | 6 | ||||
| -rw-r--r-- | monitor/monitor.c | 55 | ||||
| -rw-r--r-- | monitor/qmp.c | 122 | ||||
| -rw-r--r-- | qapi/qmp-dispatch.c | 65 | ||||
| -rw-r--r-- | qapi/qmp-registry.c | 3 | ||||
| -rw-r--r-- | util/aio-posix.c | 8 |
7 files changed, 214 insertions, 46 deletions
diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h index 9fd2b720a7..af8d96c570 100644 --- a/include/qapi/qmp/dispatch.h +++ b/include/qapi/qmp/dispatch.h @@ -31,6 +31,7 @@ typedef enum QmpCommandOptions typedef struct QmpCommand { const char *name; + /* Runs in coroutine context if QCO_COROUTINE is set */ QmpCommandFunc *fn; QmpCommandOptions options; QTAILQ_ENTRY(QmpCommand) node; diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h index b39e03b744..b55d6df07f 100644 --- a/monitor/monitor-internal.h +++ b/monitor/monitor-internal.h @@ -155,7 +155,9 @@ 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_shutdown; +extern bool qmp_dispatcher_co_busy; extern QmpCommandList qmp_commands, qmp_cap_negotiation_commands; extern QemuMutex monitor_lock; extern MonitorList mon_list; @@ -173,7 +175,7 @@ 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 ef68ca9d21..ceffe1a83b 100644 --- a/monitor/monitor.c +++ b/monitor/monitor.c @@ -55,8 +55,32 @@ 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; + +/* Set to true when the dispatcher coroutine should terminate */ +bool qmp_dispatcher_co_shutdown; + +/* + * qmp_dispatcher_co_busy is used for synchronisation between the + * monitor thread and the main thread to ensure that the dispatcher + * coroutine never gets scheduled a second time when it's already + * scheduled (scheduling the same coroutine twice is forbidden). + * + * It is true if the coroutine is active and processing requests. + * Additional requests may then be pushed onto mon->qmp_requests, + * and @qmp_dispatcher_co_shutdown may be set without further ado. + * @qmp_dispatcher_co_busy must not be woken up in this case. + * + * If false, you also have to set @qmp_dispatcher_co_busy to true and + * wake up @qmp_dispatcher_co after pushing the new requests. + * + * The coroutine will automatically change this variable back to false + * before it yields. Nobody else may set the variable to false. + * + * Access must be atomic for thread safety. + */ +bool qmp_dispatcher_co_busy; /* * Protects mon_list, monitor_qapi_event_state, coroutine_mon, @@ -623,9 +647,24 @@ 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. + * + * We need to poll both qemu_aio_context and iohandler_ctx to make + * sure that the dispatcher coroutine keeps making progress and + * eventually terminates. qemu_aio_context is automatically + * polled by calling AIO_WAIT_WHILE on it, but we must poll + * iohandler_ctx manually. + */ + qmp_dispatcher_co_shutdown = true; + if (!qatomic_xchg(&qmp_dispatcher_co_busy, true)) { + aio_co_wake(qmp_dispatcher_co); + } + + AIO_WAIT_WHILE(qemu_get_aio_context(), + (aio_poll(iohandler_get_aio_context(), false), + qatomic_mb_read(&qmp_dispatcher_co_busy))); + if (mon_iothread) { iothread_destroy(mon_iothread); mon_iothread = NULL; @@ -649,9 +688,9 @@ 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); + qatomic_mb_set(&qmp_dispatcher_co_busy, true); + aio_co_schedule(iohandler_get_aio_context(), qmp_dispatcher_co); } int monitor_init(MonitorOptions *opts, bool allow_hmp, Error **errp) diff --git a/monitor/qmp.c b/monitor/qmp.c index e746b3575d..b42f8c6af3 100644 --- a/monitor/qmp.c +++ b/monitor/qmp.c @@ -133,6 +133,10 @@ 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) { QDict *rsp; @@ -206,43 +210,99 @@ 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(qatomic_mb_read(&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); - } + /* + * Mark the dispatcher as not busy already here so that we + * don't miss any new requests coming in the middle of our + * processing. + */ + qatomic_mb_set(&qmp_dispatcher_co_busy, false); + + while (!(req_obj = monitor_qmp_requests_pop_any_with_lock())) { + /* + * No more requests to process. Wait to be reentered from + * handle_qmp_command() when it pushes more requests, or + * from monitor_cleanup() when it requests shutdown. + */ + if (!qmp_dispatcher_co_shutdown) { + qemu_coroutine_yield(); + + /* + * busy must be set to true again by whoever + * rescheduled us to avoid double scheduling + */ + assert(qatomic_xchg(&qmp_dispatcher_co_busy, false) == true); + } + + /* + * qmp_dispatcher_co_shutdown may have changed if we + * yielded and were reentered from monitor_cleanup() + */ + if (qmp_dispatcher_co_shutdown) { + return; + } + } - if (need_resume) { - /* Pairs with the monitor_suspend() in handle_qmp_command() */ - monitor_resume(&mon->common); - } - qmp_request_free(req_obj); + if (qatomic_xchg(&qmp_dispatcher_co_busy, true) == true) { + /* + * Someone rescheduled us (probably because a new requests + * came in), but we didn't actually yield. Do that now, + * only to be immediately reentered and removed from the + * list of scheduled coroutines. + */ + qemu_coroutine_yield(); + } - /* Reschedule instead of looping so the main loop stays responsive */ - qemu_bh_schedule(qmp_dispatcher_bh); + /* + * Move the coroutine from iohandler_ctx to qemu_aio_context for + * executing the command handler so that it can make progress if it + * involves an AIO_WAIT_WHILE(). + */ + 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); + + /* + * Yield and reschedule so the main loop stays responsive. + * + * Move back to iohandler_ctx so that nested event loops for + * qemu_aio_context don't start new monitor commands. + */ + aio_co_schedule(iohandler_get_aio_context(), qmp_dispatcher_co); + qemu_coroutine_yield(); + } } static void handle_qmp_command(void *opaque, QObject *req, Error *err) @@ -303,7 +363,9 @@ 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 (!qatomic_xchg(&qmp_dispatcher_co_busy, true)) { + 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 5677ba92ca..9a2d7dd29a 100644 --- a/qapi/qmp-dispatch.c +++ b/qapi/qmp-dispatch.c @@ -12,12 +12,16 @@ */ #include "qemu/osdep.h" + +#include "block/aio.h" #include "qapi/error.h" #include "qapi/qmp/dispatch.h" #include "qapi/qmp/qdict.h" #include "qapi/qmp/qjson.h" #include "sysemu/runstate.h" #include "qapi/qmp/qbool.h" +#include "qemu/coroutine.h" +#include "qemu/main-loop.h" static QDict *qmp_dispatch_check_obj(QDict *dict, bool allow_oob, Error **errp) @@ -88,6 +92,30 @@ bool qmp_is_oob(const QDict *dict) && !qdict_haskey(dict, "execute"); } +typedef struct QmpDispatchBH { + const QmpCommand *cmd; + Monitor *cur_mon; + QDict *args; + QObject **ret; + Error **errp; + Coroutine *co; +} QmpDispatchBH; + +static void do_qmp_dispatch_bh(void *opaque) +{ + QmpDispatchBH *data = opaque; + + assert(monitor_cur() == NULL); + monitor_set_cur(qemu_coroutine_self(), data->cur_mon); + data->cmd->fn(data->args, data->ret, data->errp); + monitor_set_cur(qemu_coroutine_self(), NULL); + aio_co_wake(data->co); +} + +/* + * Runs outside of coroutine context for OOB commands, but in coroutine + * context for everything else. + */ QDict *qmp_dispatch(const QmpCommandList *cmds, QObject *request, bool allow_oob, Monitor *cur_mon) { @@ -153,12 +181,39 @@ QDict *qmp_dispatch(const QmpCommandList *cmds, QObject *request, qobject_ref(args); } + assert(!(oob && qemu_in_coroutine())); assert(monitor_cur() == NULL); - monitor_set_cur(qemu_coroutine_self(), cur_mon); - - cmd->fn(args, &ret, &err); - - monitor_set_cur(qemu_coroutine_self(), NULL); + if (!!(cmd->options & QCO_COROUTINE) == qemu_in_coroutine()) { + monitor_set_cur(qemu_coroutine_self(), cur_mon); + cmd->fn(args, &ret, &err); + monitor_set_cur(qemu_coroutine_self(), NULL); + } else { + /* + * Actual context doesn't match the one the command needs. + * + * Case 1: we are in coroutine context, but command does not + * have QCO_COROUTINE. We need to drop out of coroutine + * context for executing it. + * + * Case 2: we are outside coroutine context, but command has + * QCO_COROUTINE. Can't actually happen, because we get here + * outside coroutine context only when executing a command + * out of band, and OOB commands never have QCO_COROUTINE. + */ + assert(!oob && qemu_in_coroutine() && !(cmd->options & QCO_COROUTINE)); + + QmpDispatchBH data = { + .cur_mon = cur_mon, + .cmd = cmd, + .args = args, + .ret = &ret, + .errp = &err, + .co = qemu_coroutine_self(), + }; + aio_bh_schedule_oneshot(qemu_get_aio_context(), do_qmp_dispatch_bh, + &data); + qemu_coroutine_yield(); + } qobject_unref(args); if (err) { /* or assert(!ret) after reviewing all handlers: */ diff --git a/qapi/qmp-registry.c b/qapi/qmp-registry.c index d0f9a1d3e3..58c65b5052 100644 --- a/qapi/qmp-registry.c +++ b/qapi/qmp-registry.c @@ -20,6 +20,9 @@ void qmp_register_command(QmpCommandList *cmds, const char *name, { QmpCommand *cmd = g_malloc0(sizeof(*cmd)); + /* QCO_COROUTINE and QCO_ALLOW_OOB are incompatible for now */ + assert(!((options & QCO_COROUTINE) && (options & QCO_ALLOW_OOB))); + cmd->name = name; cmd->fn = fn; cmd->enabled = true; diff --git a/util/aio-posix.c b/util/aio-posix.c index 280f27bb99..30f5354b1e 100644 --- a/util/aio-posix.c +++ b/util/aio-posix.c @@ -15,6 +15,7 @@ #include "qemu/osdep.h" #include "block/block.h" +#include "qemu/main-loop.h" #include "qemu/rcu.h" #include "qemu/rcu_queue.h" #include "qemu/sockets.h" @@ -558,8 +559,13 @@ bool aio_poll(AioContext *ctx, bool blocking) * There cannot be two concurrent aio_poll calls for the same AioContext (or * an aio_poll concurrent with a GSource prepare/check/dispatch callback). * We rely on this below to avoid slow locked accesses to ctx->notify_me. + * + * aio_poll() may only be called in the AioContext's thread. iohandler_ctx + * is special in that it runs in the main thread, but that thread's context + * is qemu_aio_context. */ - assert(in_aio_context_home_thread(ctx)); + assert(in_aio_context_home_thread(ctx == iohandler_get_aio_context() ? + qemu_get_aio_context() : ctx)); qemu_lockcnt_inc(&ctx->list_lock); |