From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 41C81C88E53 for ; Tue, 15 Sep 2026 10:50:10 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x6Qja-0004xw-E8; Tue, 15 Sep 2026 06:49:54 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1x6QjZ-0004xW-4o for qemu-devel@nongnu.org; Tue, 15 Sep 2026 06:49:53 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1x6QjW-0003NU-9W for qemu-devel@nongnu.org; Tue, 15 Sep 2026 06:49:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1789469389; 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: in-reply-to:in-reply-to:references:references; bh=aBPWYkSPpHB10jFENengvcxbGHIMIxaoHOfqaGKV9CM=; b=iHZ+EtUAPX0CaWLNVJB9bzGTQCgBzHcaVY9rnBgt79pLO2qWEXNkMntx3q839ZlKOImDS4 DvM3NIqP0Aj0TYRB2yKNET65VQNmJeKRacCc0xtB2ECnPjS6EZUV3pD8CJXfQ4eoRDAZdd pNBckud+nceMhAfyOH7hqxrgOFC6Odw= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-520-KMLirWNOPtq6zKwe_J2H7g-1; Tue, 15 Sep 2026 06:49:47 -0400 X-MC-Unique: KMLirWNOPtq6zKwe_J2H7g-1 X-Mimecast-MFC-AGG-ID: KMLirWNOPtq6zKwe_J2H7g_1789469386 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 78D321829E27; Tue, 15 Sep 2026 10:49:46 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.44.22.5]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C01C61956045; Tue, 15 Sep 2026 10:49:45 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 5C6A021E6A04; Tue, 15 Sep 2026 12:49:43 +0200 (CEST) From: Markus Armbruster To: Zhang Chen Cc: qemu-devel , Eric Blake , Markus Armbruster , "'Michael S . Tsirkin'" , Stefan Hajnoczi , Paolo Bonzini , 'Daniel P . =?utf-8?Q?Berrang=C3=A9'?= , Jason Wang Subject: Re: [PATCH V17 04/13] monitor: track IOThread users with QOM paths In-Reply-To: <20260915101655.3216101-5-zhangckid@gmail.com> (Zhang Chen's message of "Tue, 15 Sep 2026 18:16:46 +0800") References: <20260915101655.3216101-1-zhangckid@gmail.com> <20260915101655.3216101-5-zhangckid@gmail.com> Date: Tue, 15 Sep 2026 12:49:43 +0200 Message-ID: <87h5jqrdq0.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Zhang Chen writes: > Monitors that require an IOThread share the internal mon_iothread. > Account for each monitor explicitly in IOThread holder tracking, using > the monitor's canonical QOM path to distinguish holders. > > Acquire the shared monitor IOThread AioContext once and store the > IOThread and canonical QOM path so the holder can be released after the > monitor has been removed from the QOM tree. Use the stored IOThread for > per-monitor checks and accesses after initialization, and reuse the > stored context for later operations. > > Release the holder from monitor_finalize(), after resources associated > with the AioContext have been destroyed. This pairs the reference taken > in complete() with instance finalization and keeps the IOThread alive > throughout monitor teardown. > > The internal mon_iothread remains hidden from query-iothreads, as before. > Management applications therefore cannot use it to determine which > monitors are using the IOThread. Nevertheless, track the monitor > holders so that they follow the same explicit holder and > IOThread reference lifecycle as other AioContext users. > > Signed-off-by: Zhang Chen > --- > monitor/monitor-internal.h | 7 +++++-- > monitor/monitor.c | 36 ++++++++++++++++++++++++++---------- > monitor/qmp.c | 14 +++++++------- > 3 files changed, 38 insertions(+), 19 deletions(-) > > diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h > index 822a66d06d..020afdaebf 100644 > --- a/monitor/monitor-internal.h > +++ b/monitor/monitor-internal.h > @@ -77,6 +77,11 @@ struct Monitor { > GString *outbuf; > guint out_watch; > int mux_out; > + > + /* iothread context and holder identity */ > + IOThread *iothread; > + char *iothread_qom_path; > + AioContext *ctx; > }; > > struct MonitorQMPClass { > @@ -109,14 +114,12 @@ struct MonitorQMP { > }; > > typedef QTAILQ_HEAD(MonitorList, Monitor) MonitorList; > -extern IOThread *mon_iothread; > extern Coroutine *qmp_dispatcher_co; > extern bool qmp_dispatcher_co_shutdown; > extern QmpCommandList qmp_commands, qmp_cap_negotiation_commands; > extern QemuMutex monitor_lock; > extern MonitorList mon_list; > > -bool monitor_requires_iothread(const Monitor *mon); > int monitor_can_read(void *opaque); > void monitor_cancel_out_watch(Monitor *mon); > void monitor_list_append(Monitor *mon); > diff --git a/monitor/monitor.c b/monitor/monitor.c > index 2654b81890..a80d8dbf45 100644 > --- a/monitor/monitor.c > +++ b/monitor/monitor.c > @@ -55,7 +55,7 @@ typedef struct { > } MonitorQAPIEventConf; > > /* Shared monitor I/O thread */ > -IOThread *mon_iothread; > +static IOThread *mon_iothread; > > /* Coroutine to dispatch the requests received from I/O thread */ > Coroutine *qmp_dispatcher_co; > @@ -93,6 +93,16 @@ static void monitor_finalize(Object *obj) > qemu_chr_fe_deinit(&mon->chr, false); > g_string_free(mon->outbuf, true); > qemu_mutex_destroy(&mon->mon_lock); > + > + if (mon->iothread) { > + const IOThreadHolder io_holder = { > + .type = IO_THREAD_HOLDER_KIND_QOM_OBJECT, > + .u.qom_object.qom_path = mon->iothread_qom_path, > + }; > + > + iothread_unref_and_put_aio_context(mon->iothread, &io_holder); > + } > + g_free(mon->iothread_qom_path); > } > > static char *monitor_get_chardev_id(Object *obj, Error **errp) > @@ -164,7 +174,7 @@ Monitor *monitor_set_cur(Coroutine *co, Monitor *mon) > return old_monitor; > } > > -bool monitor_requires_iothread(const Monitor *mon) > +static bool monitor_requires_iothread(const Monitor *mon) > { > MonitorClass *cls = MONITOR_GET_CLASS(mon); > return cls->requires_iothread && cls->requires_iothread(mon); > @@ -188,8 +198,8 @@ void monitor_cancel_out_watch(Monitor *mon) > GMainContext *ctx = NULL; > GSource *src; > > - if (monitor_requires_iothread(mon)) { > - ctx = iothread_get_g_main_context(mon_iothread); > + if (mon->iothread) { > + ctx = iothread_get_g_main_context(mon->iothread); > } > src = g_main_context_find_source_by_id(ctx, mon->out_watch); > if (!src && ctx) { > @@ -516,12 +526,12 @@ void monitor_suspend(Monitor *mon) > { > qatomic_inc(&mon->suspend_cnt); > > - if (monitor_requires_iothread(mon)) { > + if (mon->iothread) { > /* > * Kick I/O thread to make sure this takes effect. It'll be > * evaluated again in prepare() of the watch object. > */ > - aio_notify(iothread_get_aio_context(mon_iothread)); > + aio_notify(mon->ctx); > } > > trace_monitor_suspend(mon, 1); > @@ -661,7 +671,6 @@ char *monitor_compat_id(void) > static void monitor_complete(UserCreatable *uc, Error **errp) > { > Monitor *mon = MONITOR(uc); > - AioContext *ctx; > > if (mon->chardev_id) { > Chardev *chr = qemu_chr_find(mon->chardev_id); > @@ -680,11 +689,18 @@ static void monitor_complete(UserCreatable *uc, Error **errp) > mon_iothread = iothread_create("mon_iothread", &error_abort); > } > > - ctx = iothread_get_aio_context(mon_iothread); > + mon->iothread = mon_iothread; > + mon->iothread_qom_path = object_get_canonical_path(OBJECT(mon)); Hmm, this is the monitor's QOM path, not the I/O threads. Let's rename Monitor member iothread_qom_path to monitor_qom_path or just qom_path. > + const IOThreadHolder io_holder = { > + .type = IO_THREAD_HOLDER_KIND_QOM_OBJECT, > + .u.qom_object.qom_path = mon->iothread_qom_path, > + }; > + > + mon->ctx = iothread_ref_and_get_aio_context(mon->iothread, &io_holder); > } else { > - ctx = qemu_get_aio_context(); > + mon->ctx = qemu_get_aio_context(); > } > - mon->accept_input_bh = aio_bh_new(ctx, monitor_accept_input, mon); > + mon->accept_input_bh = aio_bh_new(mon->ctx, monitor_accept_input, mon); > } > > int monitor_new(MonitorOptions *opts, bool allow_hmp, Error **errp) > diff --git a/monitor/qmp.c b/monitor/qmp.c > index aec0315775..e235302fb3 100644 > --- a/monitor/qmp.c > +++ b/monitor/qmp.c > @@ -187,7 +187,7 @@ static void monitor_qmp_caps_reset(MonitorQMP *mon) > memset(mon->capab_offered, 0, sizeof(mon->capab_offered)); > memset(mon->capab, 0, sizeof(mon->capab)); > mon->capab_offered[QMP_CAPABILITY_OOB] = > - monitor_requires_iothread(MONITOR(mon)); > + MONITOR(mon)->iothread != NULL; > } > > static void qmp_request_free(QMPRequest *req) > @@ -678,8 +678,8 @@ static void monitor_qmp_setup_handlers_bh(void *opaque) > MonitorQMP *mon = opaque; > GMainContext *context; > > - assert(monitor_requires_iothread(MONITOR(mon))); > - context = iothread_get_g_main_context(mon_iothread); > + assert(MONITOR(mon)->iothread); > + context = iothread_get_g_main_context(MONITOR(mon)->iothread); > assert(context); > qemu_chr_fe_set_handlers(&mon->parent_obj.chr, monitor_can_read, > monitor_qmp_read, monitor_qmp_event, > @@ -717,7 +717,7 @@ static void monitor_qmp_complete(UserCreatable *uc, Error **errp) > > qemu_chr_fe_set_echo(&mon->parent_obj.chr, true); > > - if (monitor_requires_iothread(MONITOR(mon))) { > + if (MONITOR(mon)->iothread) { > /* > * Make sure the old iowatch is gone. It's possible when > * e.g. the chardev is in client mode, with wait=on. > @@ -734,7 +734,7 @@ static void monitor_qmp_complete(UserCreatable *uc, Error **errp) > * thread. Schedule a bottom half. > */ > mon->setup_pending = true; > - aio_bh_schedule_oneshot(iothread_get_aio_context(mon_iothread), > + aio_bh_schedule_oneshot(MONITOR(mon)->ctx, > monitor_qmp_setup_handlers_bh, mon); > /* The bottom half will add @mon to @mon_list */ > } else { > @@ -788,8 +788,8 @@ static bool monitor_qmp_prepare_delete(UserCreatable *uc, Error **errp) > } > > /* Synchronize with in-flight iothread callbacks. */ > - if (monitor_requires_iothread(mon)) { > - aio_wait_bh_oneshot(iothread_get_aio_context(mon_iothread), > + if (mon->iothread) { > + aio_wait_bh_oneshot(mon->ctx, > monitor_qmp_iothread_quiesce, NULL); > } With the rename Reviewed-by: Markus Armbruster