From patchwork Tue Feb 18 15:40:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 11388833 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4D76B1395 for ; Tue, 18 Feb 2020 15:42:51 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 13A3422527 for ; Tue, 18 Feb 2020 15:42:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="dgIuGhwj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 13A3422527 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:37314 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j451O-0002Uf-9f for patchwork-qemu-devel@patchwork.kernel.org; Tue, 18 Feb 2020 10:42:50 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:39013) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j44zW-0006gF-VB for qemu-devel@nongnu.org; Tue, 18 Feb 2020 10:40:57 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j44zU-0001ew-MZ for qemu-devel@nongnu.org; Tue, 18 Feb 2020 10:40:54 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:34124 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1j44zU-0001ej-H9 for qemu-devel@nongnu.org; Tue, 18 Feb 2020 10:40:52 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582040452; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=a2nJJibWr+MWF10oEnk54fPJyk9Rolq9tmMWulfdPvw=; b=dgIuGhwjj87rhfO8C6CcL0CoDMeNUgd543an7PF/gDxpzSopRx0aKVA1Q7X5sFTp1PsLz/ 6I6576UQCa/02axsZIW/PSCBS1VfOjceQ/JL0cmq+ZfjTZbfmVUPnJwKlhGApz58i/VsFe KhND42qrW3LwC76DldImD50KgU3dXvo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-365-Qp2Ics0aP-mi_3ucMGTzzQ-1; Tue, 18 Feb 2020 10:40:49 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A15A5800D48; Tue, 18 Feb 2020 15:40:48 +0000 (UTC) Received: from linux.fritz.box.com (ovpn-117-181.ams2.redhat.com [10.36.117.181]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6F2AB5C13B; Tue, 18 Feb 2020 15:40:47 +0000 (UTC) From: Kevin Wolf To: qemu-devel@nongnu.org Subject: [PATCH v5 3/4] qmp: Move dispatcher to a coroutine Date: Tue, 18 Feb 2020 16:40:35 +0100 Message-Id: <20200218154036.28562-4-kwolf@redhat.com> In-Reply-To: <20200218154036.28562-1-kwolf@redhat.com> References: <20200218154036.28562-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-MC-Unique: Qp2Ics0aP-mi_3ucMGTzzQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, marcandre.lureau@gmail.com, armbru@redhat.com, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" 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 Reviewed-by: Markus Armbruster --- include/qapi/qmp/dispatch.h | 1 + monitor/monitor-internal.h | 6 +- monitor/monitor.c | 55 +++++++++++++--- monitor/qmp.c | 122 +++++++++++++++++++++++++++--------- qapi/qmp-dispatch.c | 44 ++++++++++++- qapi/qmp-registry.c | 3 + util/aio-posix.c | 7 ++- 7 files changed, 196 insertions(+), 42 deletions(-) diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h index d6ce9efc8e..6812e49b5f 100644 --- a/include/qapi/qmp/dispatch.h +++ b/include/qapi/qmp/dispatch.h @@ -30,6 +30,7 @@ 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 3e6baba88f..f8123b151a 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 c1a6c4460f..72d57b5cd2 100644 --- a/monitor/monitor.c +++ b/monitor/monitor.c @@ -53,8 +53,32 @@ 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 a 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, monitor_destroyed. */ QemuMutex monitor_lock; @@ -579,9 +603,24 @@ 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 (!atomic_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), + atomic_mb_read(&qmp_dispatcher_co_busy))); + if (mon_iothread) { iothread_destroy(mon_iothread); mon_iothread = NULL; @@ -604,9 +643,9 @@ 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); } int monitor_init_opts(QemuOpts *opts, Error **errp) diff --git a/monitor/qmp.c b/monitor/qmp.c index 8379c8f96e..d572d92e09 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) { Monitor *old_mon; @@ -211,43 +215,99 @@ 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(atomic_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. + */ + atomic_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(atomic_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 (atomic_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) @@ -308,7 +368,9 @@ 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_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 bc264b3c9b..eef09d15bc 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(const QObject *request, bool allow_oob, Error **errp) @@ -75,6 +79,25 @@ 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 +152,22 @@ 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 +202,10 @@ 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) { diff --git a/qapi/qmp-registry.c b/qapi/qmp-registry.c index ca00f74795..1b5b9f1ccc 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 a4977f538e..223de08b91 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_queue.h" #include "qemu/sockets.h" #include "qemu/cutils.h" @@ -616,7 +617,11 @@ bool aio_poll(AioContext *ctx, bool blocking) int64_t timeout; int64_t start = 0; - assert(in_aio_context_home_thread(ctx)); + /* 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 == iohandler_get_aio_context() ? + qemu_get_aio_context() : ctx)); /* aio_notify can avoid the expensive event_notifier_set if * everything (file descriptors, bottom halves, timers) will