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([2620:10d:c092:600::1:a0ed]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48541ab9f9esm517791155e9.4.2026.03.16.07.17.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 16 Mar 2026 07:17:08 -0700 (PDT) Message-ID: <2e2d6e81-bf95-47bf-9c70-1b2f8b63cfbc@gmail.com> Date: Mon, 16 Mar 2026 14:17:02 +0000 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] io_uring/poll: fix multishot recv missing EOF on wakeup race To: Jens Axboe , io-uring Cc: francis References: <8688cc4e-8619-4392-8d5c-93c554d70c34@kernel.dk> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <8688cc4e-8619-4392-8d5c-93c554d70c34@kernel.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/15/26 16:19, Jens Axboe wrote: > When a socket send and shutdown() happen back-to-back, both fire > wake-ups before the receiver's task_work has a chance to run. The first > wake gets poll ownership (poll_refs=1), and the second bumps it to 2. > When io_poll_check_events() runs, it calls io_poll_issue() which does a > recv that reads the data and returns IOU_RETRY. The loop then drains all > accumulated refs (atomic_sub_return(2) -> 0) and exits, even though only > the first event was consumed. Since the shutdown is a persistent state > change, no further wakeups will happen, and the multishot recv can hang > forever. > > Fix this by only draining a single poll ref after io_poll_issue() > returns IOU_RETRY for the APOLL_MULTISHOT path. If additional wakes > raced in (poll_refs was > 1), the loop iterates again, vfs_poll() > discovers the remaining state. How often will iterate with no effect for normal execution (i.e. no shutdown)? And how costly it'll be? Why not handle HUP instead? -- Pavel Begunkov