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 56375C5AD49 for ; Fri, 6 Jun 2025 15:44:02 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uNZEA-0006LX-4W; Fri, 06 Jun 2025 11:43:30 -0400 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 1uNZE7-0006L0-6i for qemu-devel@nongnu.org; Fri, 06 Jun 2025 11:43:27 -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 1uNZE4-000255-OT for qemu-devel@nongnu.org; Fri, 06 Jun 2025 11:43:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1749224603; 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=jImJgUIawBZnVXVa3ylGS29FiGJTmf/6EI2tleBz+bM=; b=FRSNkXM5Y/qNAgqdwg3h5E6d8DqEy4TaTQUxz/GhXILUxTkiyNcHt+levekNqboktqPzJZ ZBz7lsK0a0ixFgs6vHB7Mn4zNKkG32IyBIIftB/q/rDloTlFo9EPa3HA05eLQeqmwD7NIX LdK/g54SGE5QZUnVdgBqipOXZqH8wl0= Received: from mx-prod-mc-08.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-483-WCgKaTmVO3aDMMyM-4LixQ-1; Fri, 06 Jun 2025 11:43:17 -0400 X-MC-Unique: WCgKaTmVO3aDMMyM-4LixQ-1 X-Mimecast-MFC-AGG-ID: WCgKaTmVO3aDMMyM-4LixQ_1749224596 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3AAF91801A00; Fri, 6 Jun 2025 15:43:16 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.55]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A14C919560AE; Fri, 6 Jun 2025 15:43:13 +0000 (UTC) Date: Fri, 6 Jun 2025 16:43:10 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: JAEHOON KIM Cc: Steven Sistare , qemu-devel@nongnu.org, jjherne@linux.ibm.com, peterx@redhat.com, farosas@suse.de Subject: Re: [PATCH v1] migration: Wait for cpr.sock file to appear before connecting Message-ID: References: <20250605230808.1278840-1-jhkim@linux.ibm.com> <2f36bf89-9664-4552-86c0-646db01b7f1f@oracle.com> <2c8d3cb2-b3ee-4738-871a-0dea2bff0e84@linux.ibm.com> <3004c91e-d515-4e22-902c-42cea83ce64b@oracle.com> <760af012-1265-4845-b7d2-793fe75c3a51@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <760af012-1265-4845-b7d2-793fe75c3a51@linux.ibm.com> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.104, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=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: 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 Fri, Jun 06, 2025 at 10:37:28AM -0500, JAEHOON KIM wrote: > > On 6/6/2025 10:12 AM, Steven Sistare wrote: > > On 6/6/2025 11:06 AM, JAEHOON KIM wrote: > > > On 6/6/2025 9:14 AM, Steven Sistare wrote: > > > > On 6/6/2025 9:53 AM, Daniel P. Berrangé wrote: > > > > > On Thu, Jun 05, 2025 at 06:08:08PM -0500, Jaehoon Kim wrote: > > > > > > When the source VM attempts to connect to the destination VM's Unix > > > > > > domain socket(cpr.sock) during CPR transfer, the socket > > > > > > file might not > > > > > > yet be exist if the destination side hasn't completed the bind > > > > > > operation. This can lead to connection failures when > > > > > > running tests with > > > > > > the qtest framework. > > > > > > > > > > This sounds like a flawed test impl to me - whatever is initiating > > > > > the cpr operation on the source has done so prematurely - it should > > > > > ensure the dest is ready before starting the operation. > > > > > > > > > > > To address this, add cpr_validate_socket_path(), which wait for the > > > > > > socket file to appear. This avoids intermittent qtest > > > > > > failures caused by > > > > > > early connection attempts. > > > > > > > > > > IMHO it is dubious to special case cpr in this way. > > > > > > > > I agree with Daniel, and unfortunately it is not just a test issue; > > > > every management framework that supports cpr-transfer must add logic to > > > > wait for the cpr socket to appear in the target before proceeding. > > > > > > > > This is analogous to waiting for the monitor socket to appear before > > > > connecting to it. > > > > > > > > - Steve > > > > > > Thank you very much for your valuable review and feedback. > > > > > > Just to clarify, the added cpr_validate_socket_path() function is > > > not limited to the test framework. > > > It is part of the actual CPR implementation and is intended to > > > ensure correct behavior in all cases, including outside of tests. > > > > > > I mentioned the qtest failure simply as an example where this issue > > > became apparent. > > > > Yes, I understand that you understand :) > > Are you willing to move your fix to the qtest? > > > > - Steve > > Thank you for your question and feedback. > > I agree that the issue could be addressed within the qtest framework to > improve stability. > > However, this socket readiness check is a fundamental part of CPR transfer > process, > and I believe that incorporating cpr_validate_socket_path() directly into > the CPR implementation helps ensure more reliable behavior > across all environments - not only during testing. > > Just from my perspective, adding this logic to the CPR code does not > introduce significant overhead or side effects. > I would appreciate if you could share more details about your concerns, so I > can better address them. Requiring a busy wait like this is a sign of a design problem. There needs to be a way to setup the incoming socket listener without resorting to busy waiting - that's showing a lack of synchronization. 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 :|