Re: [PATCH v2] iio: light: vcnl4000: Fix WARN_ON on uninitialized lock

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, Jan 31, 2023 at 11:29:51AM +0100, Mårten Lindahl wrote:
> There are different init functions for the sensors in this driver in
> which only one initialize the generic vcnl4000_lock. With commit

initializes ?

> e21b5b1f2669 ("iio: light: vcnl4000: Preserve conf bits when toggle power")
> the vcnl4040 sensor started to depend on the lock, but it was missed to
> initialize it in vcnl4040's init function. This has not been visible
> until we run lockdep on it:
> 
>   DEBUG_LOCKS_WARN_ON(lock->magic != lock)
>   at kernel/locking/mutex.c:575 __mutex_lock+0x4f8/0x890
>   Call trace:
>   __mutex_lock
>   mutex_lock_nested
>   vcnl4200_set_power_state
>   vcnl4200_init
>   vcnl4000_probe
>   i2c_device_probe
>   really_probe
>   __driver_probe_device
>   driver_probe_device
>   __driver_attach
>   bus_for_each_dev
>   driver_attach
>   bus_add_driver
>   driver_register
>   i2c_register_driver
>   vcnl4000_driver_init

E.g. the following can be cut without losing significance of the data
(see below as well).

>   do_one_initcall
>   do_init_module
>   load_module
>   __do_sys_finit_module

> Fix this by initializing the lock in the probe function instead of doing
> it in the chip specific init functions.
> 
> Fixes: e21b5b1f2669 ("iio: light: vcnl4000: Preserve conf bits when toggle power")
> Signed-off-by: Mårten Lindahl <marten.lindahl@axis.com>
> ---
> 
> v2:
>  - Trimmed backtrace in commit message

Not enough, please try harder. The ideal is to have ~3-5 lines of traceback.

>  - Have 12 digit sha-1 id in Fixes tag
>  - Make the lock initialization in probe instead of in _init function

...

>  	data->client = client;
>  	data->id = id->driver_data;
>  	data->chip_spec = &vcnl4000_chip_spec_cfg[data->id];

+ Blank line.

> +	mutex_init(&data->vcnl4000_lock);
>  
>  	ret = data->chip_spec->init(data);
>  	if (ret < 0)

-- 
With Best Regards,
Andy Shevchenko