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 C220AC79F9E for ; Mon, 7 Sep 2026 12:45:31 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x3Yic-0001b1-MB; Mon, 07 Sep 2026 08:45:02 -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 1x3Yib-0001at-S0 for qemu-devel@nongnu.org; Mon, 07 Sep 2026 08:45:01 -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 1x3YiZ-0002qR-4O for qemu-devel@nongnu.org; Mon, 07 Sep 2026 08:45:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1788785097; 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=j9KXRRLSzkyAGofetJGWcuI2nc4kXnA/XwMuC2eA0zU=; b=cpofeMnPEEx+E37woupLUyaGAHY+aC86UQA0pFUbJl8NLM7vVpGnifPMgmjztvbhkSyDcQ dzm0WrRTKat8JfafeX2mUVGIwR64rzWe2cz5/p5iDRicxLFAeyXKw5Nj5Ns6wIPrSQoN3n PJFk0liQ9JLxVuQ+E+rc8aKAQdtB5Pc= 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-561-wbPYlum-OCyE4Ya-4FAukg-1; Mon, 07 Sep 2026 08:44:54 -0400 X-MC-Unique: wbPYlum-OCyE4Ya-4FAukg-1 X-Mimecast-MFC-AGG-ID: wbPYlum-OCyE4Ya-4FAukg_1788785093 Received: from mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.95]) (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 0B1721829E3F; Mon, 7 Sep 2026 12:44:53 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.44.22.5]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 531CA427; Mon, 7 Sep 2026 12:44:52 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 05B9121E6A04; Mon, 07 Sep 2026 14:44:50 +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 V15 05/14] monitor: track IOThread users with QOM paths In-Reply-To: <20260907063725.626685-6-zhangckid@gmail.com> (Zhang Chen's message of "Mon, 7 Sep 2026 14:37:16 +0800") References: <20260907063725.626685-1-zhangckid@gmail.com> <20260907063725.626685-6-zhangckid@gmail.com> Date: Mon, 07 Sep 2026 14:44:49 +0200 Message-ID: <874ig1xmbi.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 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: -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_H2=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. 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 | 5 +++++ > monitor/monitor.c | 26 +++++++++++++++++++++----- > monitor/qmp.c | 5 +++-- > 3 files changed, 29 insertions(+), 7 deletions(-) > > diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h > index 822a66d06d..1d5aeae5e6 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 { > diff --git a/monitor/monitor.c b/monitor/monitor.c > index 2654b81890..cc7f6785b5 100644 > --- a/monitor/monitor.c > +++ b/monitor/monitor.c > @@ -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) { As we'll see in monitor_complete() below, mon->iothread is mon_iothread if monitor_requires_iothread(mon), else null. Which means mon->mon_iothread is non-null if and only if monitor_requires_iothread(mon). Here, you check whether mon->mon_iothread is non-null to find out whether @mon uses the monitor I/O thread, and you read the monitor I/O thread from mon->mon_iothread. Elsewhere in this file, we check monitor_requires_iothread(mon) and you read mon_iothread, e.g. in monitor_cancel_out_watch() if (monitor_requires_iothread(mon)) { ctx = iothread_get_g_main_context(mon_iothread); } I don't like this inconsistency. Two ways to avoid it: 1. Always use monitor_requires_iothread(mon) to check and mon_iothread to read. Drop struct Monitor member iothread. 2. Always use mon_iothread, except where we initialize it in monitor_complete(). > + 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) > @@ -521,7 +531,7 @@ 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); > @@ -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) if (monitor_requires_iothread(mon)) { if (!mon_iothread) { > mon_iothread = iothread_create("mon_iothread", &error_abort); Create the single, shared monitor I/O thread on demand, and store it in mon_iothread. > } > > - ctx = iothread_get_aio_context(mon_iothread); > + mon->iothread = mon_iothread; Set mon->iothread to the monitor I/O thread. > + mon->iothread_qom_path = object_get_canonical_path(OBJECT(mon)); > + 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(); Leave mon->iothread null. > } mon->iothread is mon_iothread if monitor_requires_iothread(mon), else null. > - 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); > }