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([2a01:4b00:bd21:4f00:7cc6:d3ca:494:116c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a18be96549sm77399465e9.6.2026.10.09.04.48.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 Oct 2026 04:48:27 -0700 (PDT) Message-ID: <803bf4ba-78d8-4896-affc-7d4df5c9d50b@gmail.com> Date: Fri, 9 Oct 2026 12:48:25 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] io_uring/cmd_net: prevent infinite retry loop on unextractable timestamp skb To: Bui Viet Dung , Jens Axboe Cc: Willem de Bruijn , lollipopkit , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20b406ac-94ec-4b0f-a307-08082092ae08@gmail.com> <6ac7afc4.cf15ae49.1a8a2a.2a55@mx.google.com> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <6ac7afc4.cf15ae49.1a8a2a.2a55@mx.google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/8/26 15:59, Bui Viet Dung wrote: > On Thu, Oct 8, 2026 at 3:43 PM Pavel Begunkov wrote: >> Sounds fine since there are only timestamp skbs in this list, do >> you have a test case? > > Hi Pavel, > > Thanks for the review. > > The issue was spotted during code inspection of the error handling path > in io_uring_cmd_timestamp(): specifically when skb_get_tx_timestamp() returns > a negative error (e.g. -ENOENT due to missing PHC bindings with > SOF_TIMESTAMPING_BIND_PHC or unavailable timestamp data). Since the > multishot apoll remains armed on EPOLLERR and the unhandled skb is spliced > back onto the head of sk_error_queue, it immediately re-triggers the command > in a tight busy-loop. Thanks, I can take a look tomorrow. > Below is a standalone test program demonstrating the TX_TIMESTAMP command > setup and execution with CQE32: ...> If desired, I can format this into a test case for liburing under > test/timestamp.c. That's always appreciated! -- Pavel Begunkov