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 A75AAC61DD6 for ; Wed, 2 Sep 2026 14:38:26 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x1m68-0006vn-Bq; Wed, 02 Sep 2026 10:37:56 -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 1x1m67-0006ve-2I for qemu-devel@nongnu.org; Wed, 02 Sep 2026 10:37:55 -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 1x1m64-0001gZ-RQ for qemu-devel@nongnu.org; Wed, 02 Sep 2026 10:37:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1788359871; 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=Kyhw6BOEv0fu4+kpd75Ralujxixng8Ya42pxmqT63cY=; b=DyL9EdS9ZcQ/RN45vanbD15lam4cQASuBxO6OBXpfDprO+Als/Kf1LepNWx4jF995uyyZ+ MyZQl1yqPwLygmKkGiyKB2oTiSq2fPwEpd70em2ippGtC808dceDP5EKunIilSWqxJik2X RHLV0kuZn7CC9dcUXjxcZDNoocC2A84= 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-386-JYr6olveN_eX9EExhUEz3w-1; Wed, 02 Sep 2026 10:37:48 -0400 X-MC-Unique: JYr6olveN_eX9EExhUEz3w-1 X-Mimecast-MFC-AGG-ID: JYr6olveN_eX9EExhUEz3w_1788359867 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 81F5F1802151; Wed, 2 Sep 2026 14:37:47 +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 0978F26C; Wed, 2 Sep 2026 14:37:47 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 954F521E6837; Wed, 02 Sep 2026 16:37:44 +0200 (CEST) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Cc: Zhang Chen , qemu-devel , Eric Blake , "Michael S . Tsirkin" , Stefan Hajnoczi , Paolo Bonzini , Jason Wang Subject: Re: [PATCH V14 06/15] monitor: track IOThread users with QOM paths In-Reply-To: ("Daniel P. =?utf-8?Q?Berrang?= =?utf-8?Q?=C3=A9=22's?= message of "Wed, 2 Sep 2026 12:53:26 +0100") References: <20260831160038.221776-1-zhangckid@gmail.com> <20260831160038.221776-7-zhangckid@gmail.com> <8733vtbk16.fsf@pond.sub.org> <87qzjb3nf6.fsf@pond.sub.org> Date: Wed, 02 Sep 2026 16:37:44 +0200 Message-ID: <87jyp31zyf.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 3.6 on 10.30.177.95 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 Daniel P. Berrang=C3=A9 writes: > On Wed, Sep 02, 2026 at 01:25:33PM +0200, Markus Armbruster wrote: >> Zhang Chen writes: >>=20 >> > On Tue, Sep 1, 2026 at 1:47=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, us= ing >> >> > the monitor's canonical QOM path to distinguish holders. >> >> > >> >> > Acquire the shared monitor IOThread AioContext once, using the moni= tor >> >> > 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 b= efore. >> >> > 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()? >> > >> > >> > Add some background information in previous reviews for here: >> > https://lists.gnu.org/archive/html/qemu-devel/2026-08/msg05318.html >>=20 >> Aha, Stefan asked for monitor_finalize(), which doesn't exist. You then >> moved it to the unparent() method. > > monitor_finalize() does exist as of about a month ago. It was > introduced as part of my series that turned Monitor into a QOM > object. I was on an old branch. Sorry for the noise! >> My question for the QOM maintainers remains: is it okay to pair >> complete() with unparent(), or should it pair with prepare_delete()? > > In general most things done in complete() can/should be undone in the > finalize() callback IMHO. I can't see a finalize() callback, and I *am* on current master now. Do you mean unparent(), or do you mean monitor_finalize()? > prepare_delete() offers the opportunity to block deletion (ie prevent > QMP object_del from continuing), or (very rarely) to initiate some > cleanup that needs to take place before object properties start getting > deleted in the execution of finalize(). > > I don't think=20 > > With regards, > Daniel