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Thu, 20 Aug 2026 06:37:33 -0700 (PDT) X-Received: by 2002:a05:6820:c8e:b0:6b0:fd2d:d338 with SMTP id 006d021491bc7-6b13c6a76cdmr12379786eaf.36.1787233053462; Thu, 20 Aug 2026 06:37:33 -0700 (PDT) Received: from x1.local ([2605:8d80:6d69:ab3b:879:1f7:4951:97d9]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-6b13cebebc2sm4895056eaf.9.2026.08.20.06.37.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Aug 2026 06:37:31 -0700 (PDT) Date: Thu, 20 Aug 2026 09:37:30 -0400 From: Peter Xu To: Yanfei Xu Cc: Yanfei Xu , qemu-devel@nongnu.org, farosas@suse.de, lizhijian@fujitsu.com, Jinpu Wang Subject: Re: [PATCH 2/3] migration/rdma: Post initial receive before accepting Message-ID: References: <20260817105117.3072040-1-yanfei.xu@bytedance.com> <20260817105117.3072040-3-yanfei.xu@bytedance.com> <1313593f-9468-4779-b74e-addcdd012e8b@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1313593f-9468-4779-b74e-addcdd012e8b@gmail.com> Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.346, 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, SPF_HELO_PASS=-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: 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 On Thu, Aug 20, 2026 at 02:22:26PM +0800, Yanfei Xu wrote: > > On 2026/8/20 03:16, Peter Xu wrote: > > On Mon, Aug 17, 2026 at 06:51:16PM +0800, Yanfei Xu wrote: > > > The source return-path thread can send READY before the destination has > > > posted its initial receive. Since RNR retries default to zero, the send > > > can fail and abort migration. > > > > > > Post the initial receive before rdma_accept() to close this window. > > > > > > Fixes: 55cc1b5937a8 ("migration: create a dedicated connection for rdma return path") > > > Signed-off-by: Yanfei Xu > > This one looks correct to me, > > > > Reviewed-by: Peter Xu > > > > Do you have way to reproduce it, or is this theory (or can be reproduced by > > adding delays)? > > Yes, adding delays can reproduce it. > > For example with sleep(1) and related traces, log at source side: Thanks for the info, then let's add some of such info into the commit log, to be clear on how it would trigger (and how likely). -- Peter Xu