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 C7F56C61DD6 for ; Wed, 2 Sep 2026 11:54:06 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x1jX9-0007Bj-0d; Wed, 02 Sep 2026 07:53:39 -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 1x1jX7-0007Ba-CR for qemu-devel@nongnu.org; Wed, 02 Sep 2026 07:53:37 -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 1x1jX5-000413-NR for qemu-devel@nongnu.org; Wed, 02 Sep 2026 07:53:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1788350013; h=from:from:reply-to: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=r/Y5xJHqUyXc7Bpc7iE3eZMPmDcHnm6fxST+zd/0gWU=; b=Z7F8K/lBfFNLabGY27gjyxaXrq23zVALCGJI0m2xv6qrm+isHMyz5n35eYo4jxxI8SVxdt 1X31Bn/Itc7vHtGRa1zbeCVoO7DGy333VR7RZpltTpAavEeGsMc5OBITX1TKGIhulKUyh7 WGgh8jmGYHEAGTx5a87S3I0N5jO3adM= Received: from mx-prod-mc-05.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-57-ygI9dZX6Ma25GpzXLGlAbg-1; Wed, 02 Sept 2026 07:53:32 -0400 X-MC-Unique: ygI9dZX6Ma25GpzXLGlAbg-1 X-Mimecast-MFC-AGG-ID: ygI9dZX6Ma25GpzXLGlAbg_1788350011 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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6CC1E19539B9; Wed, 2 Sep 2026 11:53:31 +0000 (UTC) Received: from redhat.com (headnet03.pony-001.prod.iad2.dc.redhat.com [10.2.32.114]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E919A1800577; Wed, 2 Sep 2026 11:53:28 +0000 (UTC) Date: Wed, 2 Sep 2026 12:53:26 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster 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 Message-ID: References: <20260831160038.221776-1-zhangckid@gmail.com> <20260831160038.221776-7-zhangckid@gmail.com> <8733vtbk16.fsf@pond.sub.org> <87qzjb3nf6.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87qzjb3nf6.fsf@pond.sub.org> User-Agent: Mutt/2.4.0 (2026-06-19) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Sep 02, 2026 at 01:25:33PM +0200, Markus Armbruster wrote: > Zhang Chen writes: > > > On Tue, Sep 1, 2026 at 1:47 PM 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, 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()? > > > > > > Add some background information in previous reviews for here: > > https://lists.gnu.org/archive/html/qemu-devel/2026-08/msg05318.html > > 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. > 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. 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 With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|