linux-kernel - Re: [PATCH] iio: trigger: free trigger resource correctly

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Date:   Wed, 18 Jan 2017 15:11:15 -0800
From:   Alison Schofield <amsfield22@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     jic23@...nel.org, devel@...verdev.osuosl.org, lars@...afoo.de,
        Michael.Hennerich@...log.com, linux-iio@...r.kernel.org,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        pmeerw@...erw.net, knaack.h@....de
Subject: Re: [PATCH] iio: trigger: free trigger resource correctly

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@...il.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
>