Daniel Thompson bdbc65eb77 HID: i2c-hid: goodix: Fix a lockdep splat ... commit 2787710f73 upstream. I'm was on the receiving end of a lockdep splat from this driver and after scratching my head I couldn't be entirely sure it was a false positive given we would also have to think about whether the regulator locking is safe (since the notifier is called whilst holding regulator locks which are also needed for regulator_is_enabled() ). Regardless of whether it is a real bug or not, the mutex isn't needed. We can use reference counting tricks instead to avoid races with the notifier calls. The observed splat follows: ------------------------------------------------------ kworker/u16:3/127 is trying to acquire lock: ffff00008021fb20 (&ihid_goodix->regulator_mutex){+.+.}-{4:4}, at: ihid_goodix_vdd_notify+0x30/0x94 but task is already holding lock: ffff0000835c60c0 (&(&rdev->notifier)->rwsem){++++}-{4:4}, at: blocking_notifier_call_chain+0x30/0x70 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&(&rdev->notifier)->rwsem){++++}-{4:4}: down_write+0x68/0x8c blocking_notifier_chain_register+0x54/0x70 regulator_register_notifier+0x1c/0x24 devm_regulator_register_notifier+0x58/0x98 i2c_hid_of_goodix_probe+0xdc/0x158 i2c_device_probe+0x25d/0x270 really_probe+0x174/0x2cc __driver_probe_device+0xc0/0xd8 driver_probe_device+0x50/0xe4 __device_attach_driver+0xa8/0xc0 bus_for_each_drv+0x9c/0xc0 __device_attach_async_helper+0x6c/0xbc async_run_entry_fn+0x38/0x100 process_one_work+0x294/0x438 worker_thread+0x180/0x258 kthread+0x120/0x130 ret_from_fork+0x10/0x20 -> #0 (&ihid_goodix->regulator_mutex){+.+.}-{4:4}: __lock_acquire+0xd24/0xfe8 lock_acquire+0x288/0x2f4 __mutex_lock+0xa0/0x338 mutex_lock_nested+0x3c/0x5c ihid_goodix_vdd_notify+0x30/0x94 notifier_call_chain+0x6c/0x8c blocking_notifier_call_chain+0x48/0x70 _notifier_call_chain.isra.0+0x18/0x20 _regulator_enable+0xc0/0x178 regulator_enable+0x40/0x7c goodix_i2c_hid_power_up+0x18/0x20 i2c_hid_core_power_up.isra.0+0x1c/0x2c i2c_hid_core_probe+0xd8/0x3d4 i2c_hid_of_goodix_probe+0x14c/0x158 i2c_device_probe+0x25c/0x270 really_probe+0x174/0x2cc __driver_probe_device+0xc0/0xd8 driver_probe_device+0x50/0xe4 __device_attach_driver+0xa8/0xc0 bus_for_each_drv+0x9c/0xc0 __device_attach_async_helper+0x6c/0xbc async_run_entry_fn+0x38/0x100 process_one_work+0x294/0x438 worker_thread+0x180/0x258 kthread+0x120/0x130 ret_from_fork+0x10/0x20 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&(&rdev->notifier)->rwsem); lock(&ihid_goodix->regulator_mutex); lock(&(&rdev->notifier)->rwsem); lock(&ihid_goodix->regulator_mutex); *** DEADLOCK *** Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Fixes: 18eeef46d3 ("HID: i2c-hid: goodix: Tie the reset line to true state of the regulator") Reviewed-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-02-23 12:03:03 +01:00
..
i2c-hid-acpi.c	HID: i2c-hid-of: Expose the touchscreen-inverted properties	2022-01-27 11:04:41 +01:00
i2c-hid-core.c	HID: i2c-hid-of: Expose the touchscreen-inverted properties	2022-01-27 11:04:41 +01:00
i2c-hid-dmi-quirks.c	HID: i2c-hid: add Vero K147 to descriptor override	2020-11-27 16:17:49 +01:00
i2c-hid-of-goodix.c	HID: i2c-hid: goodix: Fix a lockdep splat	2022-02-23 12:03:03 +01:00
i2c-hid-of.c	HID: i2c-hid-of: Expose the touchscreen-inverted properties	2022-01-27 11:04:41 +01:00
i2c-hid.h	HID: i2c-hid-of: Expose the touchscreen-inverted properties	2022-01-27 11:04:41 +01:00
Kconfig	HID: i2c-hid: Introduce goodix-i2c-hid using i2c-hid core	2021-01-18 16:56:22 +01:00
Makefile	HID: i2c-hid: Introduce goodix-i2c-hid using i2c-hid core	2021-01-18 16:56:22 +01:00