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 lists.gnu.org (lists.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 1199DCCFA1A for ; Mon, 10 Nov 2025 16:09:47 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vIURh-0006iR-U3; Mon, 10 Nov 2025 11:08:45 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vIURf-0006e4-DC for qemu-devel@nongnu.org; Mon, 10 Nov 2025 11:08:43 -0500 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 1vIURd-0004MI-2p for qemu-devel@nongnu.org; Mon, 10 Nov 2025 11:08:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1762790920; 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=OUEc8XVVAe7WBLWj3xsxhQDqO8UoXAnA13oK6A62wvc=; b=AUmvsN1QRq4lXdNzpVagyWu3wC0aSALjhqsV0gYX9MycYPo/y5HupPsDXonyH/7sQPjKCA OkJ1kKl0k5Cuh0//+lR1UqXMMjbTvV1XwvW/EbgB1qrmMszNG/d67GruqAaRSDOrYHipa0 OsaUtJWDL0qjq5b/6DOeusqWYlx8XfU= Received: from mx-prod-mc-03.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-36-Ewku1kxhNl-VhssTl26fhA-1; Mon, 10 Nov 2025 11:08:37 -0500 X-MC-Unique: Ewku1kxhNl-VhssTl26fhA-1 X-Mimecast-MFC-AGG-ID: Ewku1kxhNl-VhssTl26fhA_1762790916 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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 281331977535; Mon, 10 Nov 2025 16:08:30 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.62]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 65583196FC91; Mon, 10 Nov 2025 16:08:28 +0000 (UTC) Date: Mon, 10 Nov 2025 16:08:24 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Eric Blake Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, kwolf@redhat.com, qemu-stable@nongnu.org Subject: Re: [PATCH v2 04/12] qio: Remember context of qio_net_listener_set_client_func_full Message-ID: References: <20251108230525.3169174-14-eblake@redhat.com> <20251108230525.3169174-18-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20251108230525.3169174-18-eblake@redhat.com> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@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, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: 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 Sat, Nov 08, 2025 at 04:59:25PM -0600, Eric Blake wrote: > io/net-listener.c has two modes of use: asynchronous (the user calls > qio_net_listener_set_client_func to wake up the callback via the > global GMainContext, or qio_net_listener_set_client_func_full to wake > up the callback via the caller's own alternative GMainContext), and > synchronous (the user calls qio_net_listener_wait_client which creates > its own GMainContext and waits for the first client connection before > returning, with no need for a user's callback). But commit 938c8b79 > has a latent logic flaw: when qio_net_listener_wait_client finishes on > its temporary context, it reverts all of the siocs back to the global > GMainContext rather than the potentially non-NULL context they might > have been originally registered with. Similarly, if the user creates > a net-listener, adds initial addresses, registers an async callback > with a non-default context (which ties to all siocs for the initial > addresses), then adds more addresses with qio_net_listener_add, the > siocs for later addresses are blindly placed in the global context, > rather than sharing the context of the earlier ones. > > In practice, I don't think this has caused issues. As pointed out by > the original commit, all async callers prior to that commit were > already okay with the NULL default context; and the typical usage > pattern is to first add ALL the addresses the listener will pay > attention to before ever setting the async callback. Likewise, if a > file uses only qio_net_listener_set_client_func instead of > qio_net_listener_set_client_func_full, then it is never using a custom > context, so later assignments of async callbacks will still be to the > same global context as earlier ones. Meanwhile, any callers that want > to do the sync operation to grab the first client are unlikely to > register an async callback; altogether bypassing the question of > whether later assignments of a GSource are being tied to a different > context over time. > > I do note that chardev/char-socket.c is the only file that calls both > qio_net_listener_wait_client (sync for a single client in > tcp_chr_accept_server_sync), and qio_net_listener_set_client_func_full > (several places, all with chr->gcontext, but sometimes with a NULL > callback function during teardown). But as far as I can tell, the two > uses are mutually exclusive, based on the is_waitconnect parameter to > qmp_chardev_open_socket_server. > > That said, it is more robust to remember when an async callback > function is tied to a non-default context, and have both the sync wait > and any late address additions honor that same context. That way, the > code will be robust even if a later user performs a sync wait for a > specific client in the middle of servicing a longer-lived > QIONetListener that has an async callback for all other clients. > > CC: qemu-stable@nongnu.org > Fixes: 938c8b79 ("qio: store gsources for net listeners", v2.12.0) > Signed-off-by: Eric Blake > > --- > v2: move earlier in series, trace context > --- > include/io/net-listener.h | 1 + > io/net-listener.c | 25 ++++++++++++++++--------- > io/trace-events | 6 +++--- > 3 files changed, 20 insertions(+), 12 deletions(-) Reviewed-by: Daniel P. Berrangé With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|