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Tue, 03 Nov 2026 08:00:44 -0800 (PST) Received: from [192.168.2.38] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-4a9219148cbsm8674533fac.3.2026.11.03.08.00.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Nov 2026 08:00:43 -0800 (PST) Message-ID: <3face247-a7b6-4f87-9863-5ad40cc272a0@kernel.dk> Date: Tue, 3 Nov 2026 09:00:42 -0700 X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: io_uring: SENDMSG/WRITEV return -EAGAIN on O_NONBLOCK socket after peer half-close To: =?UTF-8?B?THVrw6HFoSBMYWxpbnNrw70=?= Cc: io-uring@vger.kernel.org References: <6fdd17d9-0ab9-45ac-b45f-fccf085372a8@app.fastmail.com> <5475728c-6cd9-4d61-bcee-5c8a42f1951d@app.fastmail.com> Content-Language: en-US From: Jens Axboe In-Reply-To: <5475728c-6cd9-4d61-bcee-5c8a42f1951d@app.fastmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/2/26 7:00 AM, Luk?? Lalinsk? wrote: > On Thu, Oct 29, 2026, at 9:42 PM, Luk?? Lalinsk? wrote: >> There is one more inconsistency even with both patches applied: >> in the urgent data case, WRITEV on an O_NONBLOCK socket still completes >> with -EAGAIN, while SEND and SENDMSG on the same socket keep waiting. >> So whether WRITEV waits or fails depends on whether the peer sent >> urgent data, which the application can't really predict. It's not a >> problem for me, since I always use SEND/SENDMSG on sockets, but it is >> an inconsistent behavior. > > Hi Jens, > > I ran into one more issue while testing this. The SEND or SENDMSG > operations become uncancelable for a brief time after submission, > either in the half-closed state before your patches, or with the urgent > data flag after your patches. If ASYNC_CANCEL is submitted right > after the send on such socket, it completes with -ENOENT, but the > send stays pending. A second cancel issued later finds it. Without the > urgent data, the first cancel finds it and the send completes with > -ECANCELED. Your patches made it work properly for the half-closed > case. Can you try with this on top? diff --git a/io_uring/poll.c b/io_uring/poll.c index ac2979586b4f..82485e1350dd 100644 --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -739,7 +739,7 @@ int io_arm_apoll(struct io_kiocb *req, unsigned issue_flags, __poll_t mask) int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags) { const struct io_issue_def *def = &io_issue_defs[req->opcode]; - __poll_t mask = POLLPRI | POLLERR; + __poll_t mask = EPOLLERR; if (!def->pollin && !def->pollout) return IO_APOLL_ABORTED; @@ -747,7 +747,8 @@ int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags) return IO_APOLL_ABORTED; if (def->pollin) { - mask |= EPOLLIN | EPOLLRDNORM; + /* urgent data is an event for a reader only */ + mask |= EPOLLIN | EPOLLRDNORM | EPOLLPRI; /* If reading from MSG_ERRQUEUE using recvmsg, ignore POLLIN */ if (req->flags & REQ_F_CLEAR_POLLIN) -- Jens Axboe