linux-kernel - Re: get_device in device_create

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Message-ID: <20060803075236.GC28301@kroah.com>
Date:	Thu, 3 Aug 2006 00:52:36 -0700
From:	Greg KH <greg@...ah.com>
To:	Pete Zaitcev <zaitcev@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: get_device in device_create_file

On Tue, Aug 01, 2006 at 01:25:09PM -0700, Pete Zaitcev wrote:
> Hi, Greg:
> 
> This code makes no sense to me:
> 
> > int device_create_file(struct device * dev, struct device_attribute * attr)
> > {
> > 	int error = 0;
> > 	if (get_device(dev)) {
> > 		error = sysfs_create_file(&dev->kobj, &attr->attr);
> > 		put_device(dev);
> > 	}
> > 	return error;
> > }
> 
> If the struct device *dev, and its presumably enclosing structure,
> can be freed by a different CPU (or pre-empt), then get_device
> does not protect it. It can be freed before get_device is reached.
> Buf it not, and the caller has a reference, then the call to
> get_device is redundant.

Yes, it is redundant, sorry.  I know there are a few places that we
gratuitously grab references in the core that we don't really need to do
so.

It's interesting that someone would cut-and-paste from a driver core
file into something new.  What kind of code did they do that for?

Anyway, patches to clean this kind of stuff up is gladly accepted.

thanks,

greg k-h
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