Re: [PATCH] sparc: vio: use put_device() instead of kfree()

[arvindY]

On Wednesday 25 April 2018 09:14 PM, Shannon Nelson wrote:
> On 4/25/2018 7:56 AM, Arvind Yadav wrote:
> > Never directly free @dev after calling device_register(), even
> > if it returned an error. Always use put_device() to give up the
> > reference initialized.
> >
> > Signed-off-by: Arvind Yadav <arvind.yadav.cs@xxxxxxxxx>
> > ---
> >   arch/sparc/kernel/vio.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/sparc/kernel/vio.c b/arch/sparc/kernel/vio.c
> > index 1a0fa10..32bae68 100644
> > --- a/arch/sparc/kernel/vio.c
> > +++ b/arch/sparc/kernel/vio.c
> > @@ -403,7 +403,7 @@ static struct vio_dev *vio_create_one(struct 
> > mdesc_handle *hp, u64 mp,
> >       if (err) {
> >           printk(KERN_ERR "VIO: Could not register device %s, err=%d\n",
> >                  dev_name(&vdev->dev), err);
> > -        kfree(vdev);
> > +        put_device(&vdev->dev);
>
> Hmmm... I can see why the put_device() might be a good idea, but I 
> think we still need the kfree() so as to not leak the memory that was 
> kzalloc'd above for vdev.

There is no need to call kfree() here. Because put_device()
will decrement the last reference and then free the memory
by calling dev->release(It'll call vio_dev_release()).
Internally put_device() -> kobject_put() -> kobject_cleanup()
which is responsible to call 'dev -> release' and also free
other kobject resources.
If we will call kfree() here, Then It'll be a redundant call.

~arvind

> sln
>
> >           return NULL;
> >       }
> >       if (vdev->dp)