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Clark" , platform-driver-x86@vger.kernel.org, ibm-acpi-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: [BUG] thinkpad_acpi: intermittent boot hang in hotkey_poll_setup on ThinkPad X1 Carbon Gen 14 Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Hi, I am seeing an intermittent boot hang in thinkpad_acpi hotkey polling on a Lenovo ThinkPad X1 Carbon Gen 14 (machine type 21V8A028CD). I originally encountered this while testing linux-next kernels for an unrelated camera issue. The problem has occurred with at least: next-20260928 next-20261002 When it happens, boot stalls and many udev/modprobe tasks end up blocked in async_synchronize_cookie_domain(). One of the blocked tasks had the following relevant stack: hotkey_poll_setup [thinkpad_acpi] hotkey_inputdev_open [thinkpad_acpi] input_open_device kbd_connect ... tpacpi_pdriver_probe [thinkpad_acpi] ... thinkpad_acpi_module_init [thinkpad_acpi] The failure is intermittent. The same kernel can sometimes boot successfully, while another boot hangs. I tested two workarounds: 1. Blacklisting thinkpad_acpi allows the machine to boot normally. 2. More importantly, keeping thinkpad_acpi enabled but building the same kernel with only # CONFIG_THINKPAD_ACPI_HOTKEY_POLL is not set also makes boot reliable in my testing. For example, with next-20261002 I built two otherwise equivalent kernels: CONFIG_THINKPAD_ACPI=m CONFIG_THINKPAD_ACPI_HOTKEY_POLL=y and CONFIG_THINKPAD_ACPI=m # CONFIG_THINKPAD_ACPI_HOTKEY_POLL is not set The first configuration can intermittently hang during boot. With only HOTKEY_POLL disabled, the machine boots normally into KDE/Wayland and thinkpad_acpi is loaded: thinkpad_acpi 196608 0 The usual ThinkPad hotkeys I have tried also still appear to work normally with HOTKEY_POLL disabled. A normal Arch Linux 7.2.8-arch1-2 kernel boots reliably on the same machine. This therefore appears to be specifically related to the thinkpad_acpi hotkey polling path rather than thinkpad_acpi as a whole. The issue is intermittent, so I have not yet bisected it to a specific commit. I still have persistent journal logs from both successful and failed boots, and can provide complete task stacks or test additional debug patches if useful. Hardware: Lenovo ThinkPad X1 Carbon Gen 14 Machine type: 21V8A028CD Intel Core Ultra 7 356H / Panther Lake Thanks, Qiling Zhu