Re: [PATCH v3 4/4] iio: inkern: move to the cleanup.h magic

["Nuno Sá" <noname.nuno@gmail.com>]

On Sat, 2024-03-16 at 21:48 +0200, Andy Shevchenko wrote:
> Thu, Feb 29, 2024 at 04:10:28PM +0100, Nuno Sa kirjoitti:
> > Use the new cleanup magic for handling mutexes in IIO. This allows us to
> > greatly simplify some code paths.
> > 
> > While at it, also use __free(kfree) where allocations are done and drop
> > obvious comment in iio_channel_read_min().
> 
> ...
> 
> >  int iio_map_array_register(struct iio_dev *indio_dev, struct iio_map *maps)
> >  {
> > -	int i = 0, ret = 0;
> > +	int i = 0, ret;
> >  	struct iio_map_internal *mapi;
> 
> Why not making it reversed xmas tree order at the same time?
> 
> >  	if (!maps)
> >  		return 0;
> 
> ...
> 
> > -error_ret:
> > -	if (ret)
> > -		iio_map_array_unregister_locked(indio_dev);
> > -	mutex_unlock(&iio_map_list_lock);
> >  
> > +	return 0;
> > +error_ret:
> > +	iio_map_array_unregister_locked(indio_dev);
> >  	return ret;
> >  }
> 
> Do we really need to split this? (I'm fine with a new code, but seems to me as
> unneeded churn.)
> 
> ...
> 
> > +	struct iio_channel *channel __free(kfree) =
> > kzalloc(sizeof(*channel),
> > +							    GFP_KERNEL);
> 
> I would indent a bit differently:
> 
> 	struct iio_channel *channel __free(kfree) =
> 					kzalloc(sizeof(*channel),
> GFP_KERNEL);
> 
> (maybe less TABs, but you got the idea)
> 
> >  	if (!channel)
> >  		return ERR_PTR(-ENOMEM);
> 
> ...
> 
> > +	struct iio_channel *chans __free(kfree) = kcalloc(nummaps + 1,
> > +							  sizeof(*chans),
> > +							  GFP_KERNEL);
> 
> Ditto.
> 
> >  	if (!chans)
> >  		return ERR_PTR(-ENOMEM);
> 
> ...
> 
> >  	/* first find matching entry the channel map */
> > -	mutex_lock(&iio_map_list_lock);
> > -	list_for_each_entry(c_i, &iio_map_list, l) {
> > -		if ((name && strcmp(name, c_i->map->consumer_dev_name) !=
> > 0) ||
> > -		    (channel_name &&
> > -		     strcmp(channel_name, c_i->map->consumer_channel) !=
> > 0))
> > -			continue;
> > -		c = c_i;
> > -		iio_device_get(c->indio_dev);
> > -		break;
> > +	scoped_guard(mutex, &iio_map_list_lock) {
> > +		list_for_each_entry(c_i, &iio_map_list, l) {
> > +			if ((name && strcmp(name, c_i->map-
> > >consumer_dev_name) != 0) ||
> > +			    (channel_name &&
> > +			     strcmp(channel_name, c_i->map-
> > >consumer_channel) != 0))
> 
> I would kill these ' != 0' pieces, but I see they are in the original code.
> 
> > +				continue;
> > +			c = c_i;
> > +			iio_device_get(c->indio_dev);
> > +			break;
> > +		}
> >  	}
> 
> ...
> 
> > -	channel = kzalloc(sizeof(*channel), GFP_KERNEL);
> > +	struct iio_channel *channel __free(kfree) =
> > kzalloc(sizeof(*channel),
> > +							    GFP_KERNEL);
> 
> Indentation?
> 
> ...
> 
> > -error_no_chan:
> > -	kfree(channel);
> >  error_no_mem:
> >  	iio_device_put(c->indio_dev);
> >  	return ERR_PTR(err);
> 
> Effectively you move kfree after device put, would it be a problem?
> 

This one got my attention... But I think we're fine. But yeah, subtle ordering
change that I did not unnoticed.

- Nuno Sá