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 D0011C79FAD for ; Wed, 9 Sep 2026 10:40:56 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x4FjS-0001VO-3j; Wed, 09 Sep 2026 06:40:46 -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 1x4FjQ-0001VF-Fa for qemu-devel@nongnu.org; Wed, 09 Sep 2026 06:40:44 -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 1x4FjO-0002Ff-IG for qemu-devel@nongnu.org; Wed, 09 Sep 2026 06:40:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1788950440; 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=zSLTexni7kwekvkmDZtHGJ6KKF4CFvsHSGrrfyC0Wv8=; b=Ic21HD+K3ImHbm1NrHt5ITbFL9FhrmLWEkv6BAMJtE6c1srwPs/EXEXr1wsoHHhPkP94YF H65UOzJhI7U+eL/+Wv9HZTr4SIfsR0IqYsIpIs8EbJPi2NKiWgbjYmBA3l3y0P6DkDNkeK qEDngtbjFCRQVqTxA9EHKP7swrg/r6E= Received: from mx-prod-mc-08.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-344-8AnZ7JrLPRece0QnIRE7eA-1; Wed, 09 Sep 2026 06:40:39 -0400 X-MC-Unique: 8AnZ7JrLPRece0QnIRE7eA-1 X-Mimecast-MFC-AGG-ID: 8AnZ7JrLPRece0QnIRE7eA_1788950438 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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 476711800762; Wed, 9 Sep 2026 10:40:38 +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 BF7471955D84; Wed, 9 Sep 2026 10:40:37 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 5E12E21E6A04; Wed, 09 Sep 2026 12:40:35 +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 V15 05/14] monitor: track IOThread users with QOM paths In-Reply-To: (Zhang Chen's message of "Wed, 9 Sep 2026 15:57:02 +0800") References: <20260907063725.626685-1-zhangckid@gmail.com> <20260907063725.626685-6-zhangckid@gmail.com> <874ig1xmbi.fsf@pond.sub.org> Date: Wed, 09 Sep 2026 12:40:35 +0200 Message-ID: <87fqzin1wc.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 127.0.0.2 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: > On Mon, Sep 7, 2026 at 8:44=E2=80=AFPM Markus Armbruster wrote: >> >> 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 f= or >> > 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 befo= re. >> > 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 =3D 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(). > > Just to clarify: by option 2, do you mean using mon->iothread > consistently for per-monitor checks and accesses, except in > monitor_complete(), where monitor_requires_iothread() determines > whether to initialize it? Yes. I meant to write 2. Always use mon->iothread, but mistyped.