linux-kernel - get_device in device_create

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Message-Id: <20060801132509.27269013.zaitcev@redhat.com>
Date:	Tue, 1 Aug 2006 13:25:09 -0700
From:	Pete Zaitcev <zaitcev@...hat.com>
To:	greg@...ah.com
Cc:	linux-kernel@...r.kernel.org
Subject: get_device in device_create_file

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.

How is this supposed to work?

-- Pete
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