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 A4853CCF9E3 for ; Tue, 4 Nov 2025 11:26:31 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vGFAi-0004Aq-Df; Tue, 04 Nov 2025 06:25:56 -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 1vGFAe-0004A1-DE for qemu-devel@nongnu.org; Tue, 04 Nov 2025 06:25:52 -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 1vGFAb-0002Fq-G9 for qemu-devel@nongnu.org; Tue, 04 Nov 2025 06:25:51 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1762255547; 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=gOdY+hzldAKGBiGIp5gU8O5u0l/ZVznN1W4WLDRGsMY=; b=Jr13Nx0jatbvYXaEvQn/OB63UoeeIfG4ou35/K79eO6oFo4veoXGLk/bbFpdsEu7C0h1pd WTKhxyHqNAJpgxL+oD7d9x//m8QSeDvBGKz3yLXjeXs8k9Wae5UnHOwtiXkndTxO48YUP2 rRN6HGB9PEOOaccN4ViRdiJ6P4lbAoA= 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-172-pn29DpQLMPqXePvzhDMcTQ-1; Tue, 04 Nov 2025 06:25:43 -0500 X-MC-Unique: pn29DpQLMPqXePvzhDMcTQ-1 X-Mimecast-MFC-AGG-ID: pn29DpQLMPqXePvzhDMcTQ_1762255542 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 BD080195609D; Tue, 4 Nov 2025 11:25:42 +0000 (UTC) Received: from redhat.com (unknown [10.45.226.47]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3C908180044F; Tue, 4 Nov 2025 11:25:40 +0000 (UTC) Date: Tue, 4 Nov 2025 12:25:38 +0100 From: Kevin Wolf To: Eric Blake Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, berrange@redhat.com Subject: Re: [PATCH 3/8] qio: Remember context of qio_net_listener_set_client_func_full Message-ID: References: <20251103202849.3687643-10-eblake@redhat.com> <20251103202849.3687643-13-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251103202849.3687643-13-eblake@redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Am 03.11.2025 um 21:10 hat Eric Blake geschrieben: > 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 > ("qio: store gsources for net listeners", v2.12.0) 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 a 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. > > Signed-off-by: Eric Blake > @@ -160,6 +160,7 @@ void qio_net_listener_set_client_func_full(QIONetListener *listener, > listener->io_func = func; > listener->io_data = data; > listener->io_notify = notify; > + listener->context = context; Now that you show me this, I think patch 2 actually also needs to check that context is unchanged. We don't remember the old value before this patch, so maybe the order of patch 2 and 3 should be swapped. Kevin