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 24FF4C61DD6 for ; Tue, 1 Sep 2026 05:47:50 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x1HL2-000828-Bk; Tue, 01 Sep 2026 01:47:16 -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 1x1HL0-00081g-LF for qemu-devel@nongnu.org; Tue, 01 Sep 2026 01:47:14 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1x1HKx-0001Jp-Go for qemu-devel@nongnu.org; Tue, 01 Sep 2026 01:47:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1788241629; 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=7YiuaRX3OqjNJfeLIMB5MIclgvIjzC07hw6KDqhH0KA=; b=gtIlUDoXgl1xzmN+VlLI9L2imgmwev4hUG3pjpohldOluaDHvS5GRYoHEJ08ARDbWFdrmn HABKKhVk2h3cVWHR0B7AnBhTW6f5xzZMenfg1Py3WHEVhBEnJoC3okVEb5ie/DmZ+CaTki I46ZTtAhqXAB7amkdxEXMbRJdLXZsfw= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-673-8rb3LZUUNrKMWA_RNm4JCg-1; Tue, 01 Sept 2026 01:47:06 -0400 X-MC-Unique: 8rb3LZUUNrKMWA_RNm4JCg-1 X-Mimecast-MFC-AGG-ID: 8rb3LZUUNrKMWA_RNm4JCg_1788241625 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id F2A381955F2D; Tue, 1 Sep 2026 05:47:04 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.44.22.5]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 43E021800598; Tue, 1 Sep 2026 05:47:04 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id D5C7C21E6832; Tue, 01 Sep 2026 07:47:01 +0200 (CEST) From: Markus Armbruster To: Zhang Chen Cc: qemu-devel , Eric Blake , "'Michael S . Tsirkin'" , Stefan Hajnoczi , Paolo Bonzini , 'Daniel P . =?utf-8?Q?Berrang=C3=A9'?= , Jason Wang Subject: Re: [PATCH V14 06/15] monitor: track IOThread users with QOM paths In-Reply-To: <20260831160038.221776-7-zhangckid@gmail.com> (Zhang Chen's message of "Tue, 1 Sep 2026 00:00:27 +0800") References: <20260831160038.221776-1-zhangckid@gmail.com> <20260831160038.221776-7-zhangckid@gmail.com> Date: Tue, 01 Sep 2026 07:47:01 +0200 Message-ID: <8733vtbk16.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 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_H2=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no 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, using the monitor > QOM path as the holder, and reuse the stored context for later > operations. > > Release the holder from the Monitor ObjectClass::unparent callback, > while the canonical QOM path is still available. This covers every > object_unparent() path and avoids duplicating the cleanup in > monitor_cleanup() and monitor_qmp_prepare_delete(). > > 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 I have a question for our QOM experts (Paolo and Daniel). This patch takes a reference in its UserCreatableClass method complete(), and relinquishes it in its ObjectClass unparent() method. Is that correct and clean? Or should complete() pair with prepare_delete()? > --- > monitor/monitor-internal.h | 3 +++ > monitor/monitor.c | 33 ++++++++++++++++++++++++++++----- > monitor/qmp.c | 5 +++-- > 3 files changed, 34 insertions(+), 7 deletions(-) > > diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h > index e0a124a317..74ea15c85f 100644 > --- a/monitor/monitor-internal.h > +++ b/monitor/monitor-internal.h > @@ -154,6 +154,9 @@ struct Monitor { > guint out_watch; > int mux_out; > int reset_seen; > + > + /* iothread context */ > + AioContext *ctx; > }; > > struct MonitorHMPClass { > diff --git a/monitor/monitor.c b/monitor/monitor.c > index 6af09f2f6e..9e3b639eff 100644 > --- a/monitor/monitor.c > +++ b/monitor/monitor.c > @@ -81,6 +81,22 @@ int monitor_device_index; > OBJECT_DEFINE_TYPE_EXTENDED(Monitor, monitor, MONITOR, OBJECT, true, > { TYPE_USER_CREATABLE }, {}); > > +static void monitor_unparent(Object *obj) > +{ > + Monitor *mon = MONITOR(obj); > + > + if (mon->ctx && monitor_requires_iothread(mon)) { > + g_autofree char *path = object_get_canonical_path(obj); > + const IOThreadHolder io_holder = { > + .type = IO_THREAD_HOLDER_KIND_QOM_OBJECT, > + .u.qom_object.qom_path = path, > + }; > + > + iothread_unref_and_put_aio_context(mon_iothread, &io_holder); > + mon->ctx = NULL; > + } > +} > + > static void monitor_finalize(Object *obj) > { > Monitor *mon = MONITOR(obj); > @@ -116,6 +132,8 @@ static void monitor_class_init(ObjectClass *cls, const void *data) > { > UserCreatableClass *ucc = USER_CREATABLE_CLASS(cls); > > + cls->unparent = monitor_unparent; > + > object_class_property_add_str(cls, "chardev", > monitor_get_chardev_id, > monitor_set_chardev_id); > @@ -575,7 +593,7 @@ void monitor_suspend(Monitor *mon) > * 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); > @@ -715,7 +733,6 @@ 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); > @@ -734,11 +751,17 @@ static void monitor_complete(UserCreatable *uc, Error **errp) > mon_iothread = iothread_create("mon_iothread", &error_abort); > } > > - ctx = iothread_get_aio_context(mon_iothread); > + g_autofree char *path = object_get_canonical_path(OBJECT(mon)); > + const IOThreadHolder io_holder = { > + .type = IO_THREAD_HOLDER_KIND_QOM_OBJECT, > + .u.qom_object.qom_path = 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..de56345456 100644 > --- a/monitor/qmp.c > +++ b/monitor/qmp.c > @@ -734,7 +734,8 @@ 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 { > @@ -789,7 +790,7 @@ 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), > + aio_wait_bh_oneshot(MONITOR(mon)->ctx, > monitor_qmp_iothread_quiesce, NULL); > }