Re: [PATCH v3] iio: light: vcnl4000: Fix WARN_ON on uninitialized lock

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 31 Jan 2023 16:14:11 +0200
Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> On Tue, Jan 31, 2023 at 03:01:09PM +0100, Mårten Lindahl wrote:
> > There are different init functions for the sensors in this driver in
> > which only one initializes the generic vcnl4000_lock. With commit
> > 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
> > 
> > Fix this by initializing the lock in the probe function instead of doing
> > it in the chip specific init functions.  
> 
> Fine now, thanks!
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> 
> > Fixes: e21b5b1f2669 ("iio: light: vcnl4000: Preserve conf bits when toggle power")
> > Signed-off-by: Mårten Lindahl <marten.lindahl@axis.com>
Applied to the fixes-togreg branch and marked for stable.

Thanks,

Jonathan

> > ---
> > 
> > v3:
> >  - Trimmed backtrace in commit message even more
> >  - New line before mutex_init
> > 
> > v2:
> >  - Trimmed backtrace in commit message
> >  - Have 12 digit sha-1 id in Fixes tag
> >  - Make the lock initialization in probe instead of in _init function
> > 
> >  drivers/iio/light/vcnl4000.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iio/light/vcnl4000.c b/drivers/iio/light/vcnl4000.c
> > index cc1a2062e76d..69c5bc987e26 100644
> > --- a/drivers/iio/light/vcnl4000.c
> > +++ b/drivers/iio/light/vcnl4000.c
> > @@ -199,7 +199,6 @@ static int vcnl4000_init(struct vcnl4000_data *data)
> >  
> >  	data->rev = ret & 0xf;
> >  	data->al_scale = 250000;
> > -	mutex_init(&data->vcnl4000_lock);
> >  
> >  	return data->chip_spec->set_power_state(data, true);
> >  };
> > @@ -1197,6 +1196,8 @@ static int vcnl4000_probe(struct i2c_client *client)
> >  	data->id = id->driver_data;
> >  	data->chip_spec = &vcnl4000_chip_spec_cfg[data->id];
> >  
> > +	mutex_init(&data->vcnl4000_lock);
> > +
> >  	ret = data->chip_spec->init(data);
> >  	if (ret < 0)
> >  		return ret;
> > -- 
> > 2.30.2
> >   
>