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Commit 099d1c29 authored by David Herrmann's avatar David Herrmann
Browse files

drm: provide device-refcount 



Lets not trick ourselves into thinking "drm_device" objects are not
ref-counted. That's just utterly stupid. We manage "drm_minor" objects on
each drm-device and each minor can have an unlimited number of open
handles. Each of these handles has the drm_minor (and thus the drm_device)
as private-data in the file-handle. Therefore, we may not destroy
"drm_device" until all these handles are closed.

It is *not* possible to reset all these pointers atomically and restrict
access to them, and this is *not* how this is done! Instead, we use
ref-counts to make sure the object is valid and not freed.

Note that we currently use "dev->open_count" for that, which is *exactly*
the same as a reference-count, just open coded. So this patch doesn't
change any semantics on DRM devices (well, this patch just introduces the
ref-count, anyway. Follow-up patches will replace open_count by it).

Also note that generic VFS revoke support could allow us to drop this
ref-count again. We could then just synchronously disable any fops->xy()
calls. However, this is not the case, yet, and no such patches are
in sight (and I seriously question the idea of dropping the ref-cnt
again).

Signed-off-by: default avatarDavid Herrmann <dh.herrmann@gmail.com>
parent cb8a239b

drivers/gpu/drm/drm_pci.c

+1 −1
Original line number Diff line number Diff line
@@ -351,7 +351,7 @@ int drm_get_pci_dev(struct pci_dev *pdev, const struct pci_device_id *ent, 
	drm_pci_agp_destroy(dev);

	pci_disable_device(pdev);

err_free:

	drm_dev_free(dev);

	drm_dev_unref(dev);

	return ret;

}

EXPORT_SYMBOL(drm_get_pci_dev);

drivers/gpu/drm/drm_platform.c

+1 −1
Original line number Diff line number Diff line
@@ -64,7 +64,7 @@ static int drm_get_platform_dev(struct platform_device *platdev, 
	return 0;



err_free:

	drm_dev_free(dev);

	drm_dev_unref(dev);

	return ret;

}

drivers/gpu/drm/drm_stub.c

+42 −14
Original line number Diff line number Diff line
@@ -392,7 +392,7 @@ void drm_put_dev(struct drm_device *dev) 
	}



	drm_dev_unregister(dev);

	drm_dev_free(dev);

	drm_dev_unref(dev);

}

EXPORT_SYMBOL(drm_put_dev);
@@ -425,6 +425,9 @@ EXPORT_SYMBOL(drm_unplug_dev); 
 * Call drm_dev_register() to advertice the device to user space and register it

 * with other core subsystems.

 *

 * The initial ref-count of the object is 1. Use drm_dev_ref() and

 * drm_dev_unref() to take and drop further ref-counts.

 *

 * RETURNS:

 * Pointer to new DRM device, or NULL if out of memory.

 */
@@ -438,6 +441,7 @@ struct drm_device *drm_dev_alloc(struct drm_driver *driver, 
	if (!dev)

		return NULL;



	kref_init(&dev->ref);

	dev->dev = parent;

	dev->driver = driver;
@@ -481,18 +485,10 @@ struct drm_device *drm_dev_alloc(struct drm_driver *driver, 
}

EXPORT_SYMBOL(drm_dev_alloc);



/**

 * drm_dev_free - Free DRM device

 * @dev: DRM device to free

 *

 * Free a DRM device that has previously been allocated via drm_dev_alloc().

 * You must not use kfree() instead or you will leak memory.

 *

 * This must not be called once the device got registered. Use drm_put_dev()

 * instead, which then calls drm_dev_free().

 */

void drm_dev_free(struct drm_device *dev)

static void drm_dev_release(struct kref *ref)

{

	struct drm_device *dev = container_of(ref, struct drm_device, ref);



	drm_put_minor(dev->control);

	drm_put_minor(dev->render);

	drm_put_minor(dev->primary);
@@ -506,7 +502,39 @@ void drm_dev_free(struct drm_device *dev) 
	kfree(dev->devname);

	kfree(dev);

}

EXPORT_SYMBOL(drm_dev_free);



/**

 * drm_dev_ref - Take reference of a DRM device

 * @dev: device to take reference of or NULL

 *

 * This increases the ref-count of @dev by one. You *must* already own a

 * reference when calling this. Use drm_dev_unref() to drop this reference

 * again.

 *

 * This function never fails. However, this function does not provide *any*

 * guarantee whether the device is alive or running. It only provides a

 * reference to the object and the memory associated with it.

 */

void drm_dev_ref(struct drm_device *dev)

{

	if (dev)

		kref_get(&dev->ref);

}

EXPORT_SYMBOL(drm_dev_ref);



/**

 * drm_dev_unref - Drop reference of a DRM device

 * @dev: device to drop reference of or NULL

 *

 * This decreases the ref-count of @dev by one. The device is destroyed if the

 * ref-count drops to zero.

 */

void drm_dev_unref(struct drm_device *dev)

{

	if (dev)

		kref_put(&dev->ref, drm_dev_release);

}

EXPORT_SYMBOL(drm_dev_unref);



/**

 * drm_dev_register - Register DRM device
@@ -581,7 +609,7 @@ EXPORT_SYMBOL(drm_dev_register); 
 *

 * Unregister the DRM device from the system. This does the reverse of

 * drm_dev_register() but does not deallocate the device. The caller must call

 * drm_dev_free() to free all resources.

 * drm_dev_unref() to drop their final reference.

 */

void drm_dev_unregister(struct drm_device *dev)

{

drivers/gpu/drm/drm_usb.c

+1 −1
Original line number Diff line number Diff line
@@ -30,7 +30,7 @@ int drm_get_usb_dev(struct usb_interface *interface, 
	return 0;



err_free:

	drm_dev_free(dev);

	drm_dev_unref(dev);

	return ret;



}

drivers/gpu/drm/tegra/bus.c

+1 −1
Original line number Diff line number Diff line
@@ -63,7 +63,7 @@ int drm_host1x_init(struct drm_driver *driver, struct host1x_device *device) 
	return 0;



err_free:

	drm_dev_free(drm);

	drm_dev_unref(drm);

	return ret;

}