Re: [PATCH] iio: trigger: free trigger resource correctly

From: Alison Schofield <amsfield22@gmail.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: jic23@kernel.org, devel@driverdev.osuosl.org, lars@metafoo.de,
	Michael.Hennerich@analog.com, linux-iio@vger.kernel.org,
	gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
	pmeerw@pmeerw.net, knaack.h@gmx.de
Subject: Re: [PATCH] iio: trigger: free trigger resource correctly
Date: Wed, 18 Jan 2017 15:11:15 -0800	[thread overview]
Message-ID: <20170118231113.GA5112@d830.WORKGROUP> (raw)
In-Reply-To: <20170118095629.GA4454@mwanda>

On Wed, Jan 18, 2017 at 12:56:29PM +0300, Dan Carpenter wrote:
> On Tue, Jan 17, 2017 at 07:00:28PM -0800, Alison Schofield wrote:
> > Using iio_trigger_put() to free a trigger leads to release of
> > a resource we never held.  Replace with iio_trigger_free().
> 
> They're basically the same except iio_trigger_put() puts the module and
> the device and free only puts the device.
> 
> I've looked at this briefly, but I can't figure out how iio_trigger_get/
> iio_trigger_put is supposed to be used.  There isn't any documentation.
> I'm trying to review this code, but I can't figure out where we *are*
> supposed to be doing the put.
> 
> For example, iio_device_unregister_trigger_consumer() takes a put, but
> iio_device_register_trigger_consumer() doesn't do a get...  It's all
> very confusing.
> 
> You seem like you know what's going on.  Can we get some documentation?
> 
Dan,
Although I'm comfortable within the bounds of this fix (pair the  
alloc & free's and do not _put the module resource we never _get'd) 
beyond that, not so much.  I'm just figuring it out myself.

linux-iio experts...pointers, help?

alisons

> > 
> > Signed-off-by: Alison Schofield <amsfield22@gmail.com>
> > ---
> > Patches to use devm_* funcs are ready to follow this for
> > the interrupt & bfin-timer triggers.
> > 
> >  drivers/iio/trigger/iio-trig-interrupt.c          | 4 ++--
> >  drivers/iio/trigger/iio-trig-sysfs.c              | 2 +-
> >  drivers/staging/iio/trigger/iio-trig-bfin-timer.c | 4 ++--
> >  3 files changed, 5 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/iio/trigger/iio-trig-interrupt.c b/drivers/iio/trigger/iio-trig-interrupt.c
> > index 572bc6f..b18e50d 100644
> > --- a/drivers/iio/trigger/iio-trig-interrupt.c
> > +++ b/drivers/iio/trigger/iio-trig-interrupt.c
> > @@ -84,7 +84,7 @@ static int iio_interrupt_trigger_probe(struct platform_device *pdev)
> >  error_free_trig_info:
> >  	kfree(trig_info);
> >  error_put_trigger:
> > -	iio_trigger_put(trig);
> > +	iio_trigger_free(trig);
> 
> 
> We could rename this label.
> 
> regards,
> dan carpenter
> 