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([2620:10d:c092:600::1:558d]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5f625833be4sm5818271a12.50.2025.04.22.00.58.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Apr 2025 00:58:59 -0700 (PDT) Message-ID: <1c141101-035f-4ff6-a260-f31dca39fdc8@gmail.com> Date: Tue, 22 Apr 2025 09:00:14 +0100 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: Add new functions to handle user fault scenarios To: Zhiwei Jiang , axboe@kernel.dk Cc: io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250422030153.1166445-1-qq282012236@gmail.com> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <20250422030153.1166445-1-qq282012236@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/22/25 04:01, Zhiwei Jiang wrote: ... > I tracked the address that triggered the fault and the related function > graph, as well as the wake-up side of the user fault, and discovered this > : In the IOU worker, when fault in a user space page, this space is > associated with a userfault but does not sleep. This is because during > scheduling, the judgment in the IOU worker context leads to early return. > Meanwhile, the listener on the userfaultfd user side never performs a COPY > to respond, causing the page table entry to remain empty. However, due to > the early return, it does not sleep and wait to be awakened as in a normal > user fault, thus continuously faulting at the same address,so CPU loop. > > Therefore, I believe it is necessary to specifically handle user faults by > setting a new flag to allow schedule function to continue in such cases, > make sure the thread to sleep.Export the relevant functions and struct for > user fault. That's an interesting scenario. Not looking deeper into it, I don't see any callers to set_userfault_flag_for_ioworker(), and so there is no one to set IO_WORKER_F_FAULT. Is there a second patch patch I lost? -- Pavel Begunkov