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Wed, 19 Aug 2026 23:22:30 -0700 (PDT) Received: from [10.3.188.167] ([61.213.176.5]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-395ada1deabsm425914a91.2.2026.08.19.23.22.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Aug 2026 23:22:29 -0700 (PDT) Message-ID: <1313593f-9468-4779-b74e-addcdd012e8b@gmail.com> Date: Thu, 20 Aug 2026 14:22:26 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/3] migration/rdma: Post initial receive before accepting To: Peter Xu , Yanfei Xu Cc: qemu-devel@nongnu.org, farosas@suse.de, lizhijian@fujitsu.com, Jinpu Wang References: <20260817105117.3072040-1-yanfei.xu@bytedance.com> <20260817105117.3072040-3-yanfei.xu@bytedance.com> From: Yanfei Xu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::62d; envelope-from=isyanfei.xu@gmail.com; helo=mail-pl1-x62d.google.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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, 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: 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 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: 2026-08-20T05:55:11.471421Z qemu_rdma_exchange_get_response_start CONTROL: READY receiving... 2026-08-20T05:55:11.471422Z qemu_rdma_post_send_control CONTROL: sending QEMU FILE.. 2026-08-20T05:55:11.471447Z qemu_rdma_poll_other other completion 2000 received left 0 2026-08-20T05:55:11.471589Z qemu_rdma_poll_recv completion 0 received (4000) left 0 2026-08-20T05:55:11.471592Z qemu_rdma_poll_other other completion 4000 received left 0 2026-08-20T05:55:11.471594Z qemu_rdma_exchange_get_response_start CONTROL: READY receiving... 2026-08-20T05:55:11.471596Z qemu_rdma_post_send_control CONTROL: sending QEMU FILE.. 2026-08-20T05:55:11.471617Z qemu_rdma_poll_other other completion 2000 received left 0 2026-08-20T05:55:11.705561Z qemu_rdma_close 2026-08-20T05:55:11.705587Z qemu_rdma_close 2026-08-20T05:55:11.705626Z qemu-system-x86_64: rdma migration: send polling control error 2026-08-20T05:55:11.707001Z qemu-system-x86_64: warning: Early error. Sending error. 2026-08-20T05:55:11.707031Z qemu_rdma_post_send_control CONTROL: sending ERROR.. 2026-08-20T05:55:11.707038Z qemu-system-x86_64: warning: rdma migration: send polling control error 2026-08-20T05:55:11.707301Z qemu_rdma_cleanup_disconnect 2026-08-20T05:55:11.710569Z qemu_rdma_cleanup_disconnect Regards, Yanfei