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([2001:a61:1382:1301:13e6:2b3f:f0bc:1e1c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3ca6240b4e1sm1088151f8f.21.2025.08.25.02.50.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 25 Aug 2025 02:50:10 -0700 (PDT) Message-ID: Date: Mon, 25 Aug 2025 11:50:10 +0200 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] usb: usbfs: Add reset_resume callback to usbfs. To: =?UTF-8?B?6Ieq5bex?= , Alan Stern Cc: gregkh@linuxfoundation.org, jannh@google.com, rex.nie@jaguarmicro.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, chenchangcheng References: <20250822024602.42894-1-ccc194101@163.com> <4cdaecd1.131d.198dedeefe2.Coremail.ccc194101@163.com> <379c80f7-aa01-4575-aa0b-d64ef01c1346@rowland.harvard.edu> <23f1c6c2.2011.198df066c15.Coremail.ccc194101@163.com> Content-Language: en-US From: Oliver Neukum In-Reply-To: <23f1c6c2.2011.198df066c15.Coremail.ccc194101@163.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 8/25/25 04:19, 自己 wrote: > According to the current experimental findings, when userspace encounters > an error while using the previous file descriptor (fd), it does not proceed to unbind > and rebind automatically. Therefore, the two uevents were added in the kernel to explicitly > notify userspace to unbind and rebind. Sure, but that means that user space has a bug. That race is present in every case. Even if the kernel were to notify user space by additional channels, user space could already be in the process of calling into the kernel. There is no way of avoiding the need for user space to handle this error return correctly. Regards Oliver