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 EBE31C61DD3 for ; Thu, 3 Sep 2026 06:05:38 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x20Zh-0006SZ-CI; Thu, 03 Sep 2026 02:05:25 -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 1x20Zf-0006On-QG for qemu-devel@nongnu.org; Thu, 03 Sep 2026 02:05:23 -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 1x20Ze-0007sX-0r for qemu-devel@nongnu.org; Thu, 03 Sep 2026 02:05:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1788415520; 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=XNAlIZONo9Veshj1Ood70durc7fmRGGI7FM3Iujq90g=; b=U+0A/E4u0PygyjOEdkuyr5t9W5JSOl7unyhVO+I6ycNzUyZx+JrAiFfVQ9xTz0TCCU0ooo JqMo6LERIKHIRlmkJGABpmz3CdLMxx5lJudRRfDd1cmJrK7E1mMZ2qXHJRvRJ+CsoZHt4M aje+JEhIGO2nvM0VMCWJrtK8mugkVOo= 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-316-zd1sCxlBO_mh19sfxhW_Bw-1; Thu, 03 Sep 2026 02:05:18 -0400 X-MC-Unique: zd1sCxlBO_mh19sfxhW_Bw-1 X-Mimecast-MFC-AGG-ID: zd1sCxlBO_mh19sfxhW_Bw_1788415517 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 ADD831956080; Thu, 3 Sep 2026 06:05:17 +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 22FA318005BA; Thu, 3 Sep 2026 06:05:17 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id B20BD21E6837; Thu, 03 Sep 2026 08:05:14 +0200 (CEST) From: Markus Armbruster To: Stefan Hajnoczi Cc: Zhang Chen , qemu-devel , Eric Blake , Markus Armbruster , "'Michael S . Tsirkin'" , 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: <20260902193518.GB787498@fedora> (Stefan Hajnoczi's message of "Wed, 2 Sep 2026 15:35:18 -0400") References: <20260831160038.221776-1-zhangckid@gmail.com> <20260831160038.221776-7-zhangckid@gmail.com> <20260902193518.GB787498@fedora> Date: Thu, 03 Sep 2026 08:05:14 +0200 Message-ID: <87ik4mzx7p.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=170.10.133.124; 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_H3=0.001, RCVD_IN_MSPIKE_WL=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 Stefan Hajnoczi writes: > On Tue, Sep 01, 2026 at 12:00:27AM +0800, Zhang Chen wrote: >> 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 >> --- >> 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; > > mon->accept_input_bh still exits and uses the AioContext at this point > (it is freed in monitor_finalize()). Strictly speaking, this violates > the idea of not using the AioContext anymore after calling > iothread_unref_and_put_aio_context(). > > This could be a source of bugs, but mon->accept_input_bh won't be > scheduled anymore in this code path, so I think we can live with this. Worth a comment? > Reviewed-by: Stefan Hajnoczi