Commit dc4c15d44b2b43279b2667baa7645c65c2ff960e

Authored by Jean Delvare
Committed by Greg Kroah-Hartman
1 parent c7308c81a8

platform: reorder platform_device_del

In platform_device_del(), we currently delete the device resources
first, then we delete the device itself. This causes a (minor) bug to
occur when one unregisters a platform device before unregistering its
platform driver, and the driver is requesting (in .probe()) and
releasing (in .remove()) a resource of the device. The device
resources are already gone by the time the driver gets the chance to
release the resources it had been requesting, causing an error like:
Trying to free nonexistent resource <0000000000000295-0000000000000296>

If the platform driver is unregistered first, the problem doesn't
occur, as the driver will have the opportunity to release the
resources it had requested before the device resources themselves are
released. It's a bit odd that unregistering the driver first or the
device first doesn't lead to the same result.

So I believe that we should delete the device first in
platform_device_del(). I've searched the git history and found that it
used to be the case before 2.6.8, but was changed here:

http://www.kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commitdiff;h=96ef7b3689936ee1e64b711511342026a8ce459c

> 2004/07/14 16:09:44-07:00 dtor_core
> [PATCH] Driver core: Fix OOPS in device_platform_unregister
>
> Driver core: platform_device_unregister should release resources first
>              and only then call device_unregister, otherwise if there
>              are no more references to the device it will be freed and
>              the fucntion will try to access freed memory.

However we now have an explicit call to put_device() at the end of
platform_device_unregister() so I guess the original problem no longer
exists and it is safe to revert that change.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Showing 1 changed file with 5 additions and 3 deletions Side-by-side Diff

drivers/base/platform.c
... ... @@ -292,20 +292,22 @@
292 292 * @pdev: platform device we're removing
293 293 *
294 294 * Note that this function will also release all memory- and port-based
295   - * resources owned by the device (@dev->resource).
  295 + * resources owned by the device (@dev->resource). This function
  296 + * must _only_ be externally called in error cases. All other usage
  297 + * is a bug.
296 298 */
297 299 void platform_device_del(struct platform_device *pdev)
298 300 {
299 301 int i;
300 302  
301 303 if (pdev) {
  304 + device_del(&pdev->dev);
  305 +
302 306 for (i = 0; i < pdev->num_resources; i++) {
303 307 struct resource *r = &pdev->resource[i];
304 308 if (r->flags & (IORESOURCE_MEM|IORESOURCE_IO))
305 309 release_resource(r);
306 310 }
307   -
308   - device_del(&pdev->dev);
309 311 }
310 312 }
311 313 EXPORT_SYMBOL_GPL(platform_device_del);