On 03/16/2016 06:04 AM, Mauro Carvalho Chehab wrote:
> Now that the media_device can be used by multiple drivers,
> via devres, we need to be sure that it will be dropped only
> when all drivers stop using it.
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx>
Tested bind_unbind au0828 loop 1000 times, followed by bind_unbind
snd_usb_audio loop 1000 times. Didn't see any lock warnings on a
KASAN enabled kernel (lock testing enabled). No use-after-free errors
during these runs.
Ran device removal test and rmmod and modprobe tests on both drivers.
Generated graph after the runs and the graph looks good.
Reviewed-by: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>
Tested-by: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>
thanks,
-- Shuah
> ---
> drivers/media/media-device.c | 48 +++++++++++++++++++++++++++++++-------------
> include/media/media-device.h | 3 +++
> 2 files changed, 37 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
> index c32fa15cc76e..38e6c319fe6e 100644
> --- a/drivers/media/media-device.c
> +++ b/drivers/media/media-device.c
> @@ -721,6 +721,15 @@ int __must_check __media_device_register(struct media_device *mdev,
> {
> int ret;
>
> + /* Check if mdev was ever registered at all */
> + mutex_lock(&mdev->graph_mutex);
> + if (media_devnode_is_registered(&mdev->devnode)) {
> + kref_get(&mdev->kref);
> + mutex_unlock(&mdev->graph_mutex);
> + return 0;
> + }
> + kref_init(&mdev->kref);
> +
> /* Register the device node. */
> mdev->devnode.fops = &media_device_fops;
> mdev->devnode.parent = mdev->dev;
> @@ -730,8 +739,10 @@ int __must_check __media_device_register(struct media_device *mdev,
> mdev->topology_version = 0;
>
> ret = media_devnode_register(&mdev->devnode, owner);
> - if (ret < 0)
> + if (ret < 0) {
> + media_devnode_unregister(&mdev->devnode);
> return ret;
> + }
>
> ret = device_create_file(&mdev->devnode.dev, &dev_attr_model);
> if (ret < 0) {
> @@ -739,6 +750,7 @@ int __must_check __media_device_register(struct media_device *mdev,
> return ret;
> }
>
> + mutex_unlock(&mdev->graph_mutex);
> dev_dbg(mdev->dev, "Media device registered\n");
>
> return 0;
> @@ -773,23 +785,15 @@ void media_device_unregister_entity_notify(struct media_device *mdev,
> }
> EXPORT_SYMBOL_GPL(media_device_unregister_entity_notify);
>
> -void media_device_unregister(struct media_device *mdev)
> +static void do_media_device_unregister(struct kref *kref)
> {
> + struct media_device *mdev;
> struct media_entity *entity;
> struct media_entity *next;
> struct media_interface *intf, *tmp_intf;
> struct media_entity_notify *notify, *nextp;
>
> - if (mdev == NULL)
> - return;
> -
> - mutex_lock(&mdev->graph_mutex);
> -
> - /* Check if mdev was ever registered at all */
> - if (!media_devnode_is_registered(&mdev->devnode)) {
> - mutex_unlock(&mdev->graph_mutex);
> - return;
> - }
> + mdev = container_of(kref, struct media_device, kref);
>
> /* Remove all entities from the media device */
> list_for_each_entry_safe(entity, next, &mdev->entities, graph_obj.list)
> @@ -807,13 +811,26 @@ void media_device_unregister(struct media_device *mdev)
> kfree(intf);
> }
>
> - mutex_unlock(&mdev->graph_mutex);
> + /* Check if mdev devnode was registered */
> + if (!media_devnode_is_registered(&mdev->devnode))
> + return;
>
> device_remove_file(&mdev->devnode.dev, &dev_attr_model);
> media_devnode_unregister(&mdev->devnode);
>
> dev_dbg(mdev->dev, "Media device unregistered\n");
> }
> +
> +void media_device_unregister(struct media_device *mdev)
> +{
> + if (mdev == NULL)
> + return;
> +
> + mutex_lock(&mdev->graph_mutex);
> + kref_put(&mdev->kref, do_media_device_unregister);
> + mutex_unlock(&mdev->graph_mutex);
> +
> +}
> EXPORT_SYMBOL_GPL(media_device_unregister);
>
> static void media_device_release_devres(struct device *dev, void *res)
> @@ -825,13 +842,16 @@ struct media_device *media_device_get_devres(struct device *dev)
> struct media_device *mdev;
>
> mdev = devres_find(dev, media_device_release_devres, NULL, NULL);
> - if (mdev)
> + if (mdev) {
> + kref_get(&mdev->kref);
> return mdev;
> + }
>
> mdev = devres_alloc(media_device_release_devres,
> sizeof(struct media_device), GFP_KERNEL);
> if (!mdev)
> return NULL;
> +
> return devres_get(dev, mdev, NULL, NULL);
> }
> EXPORT_SYMBOL_GPL(media_device_get_devres);
> diff --git a/include/media/media-device.h b/include/media/media-device.h
> index ca3871b853ba..73c16e6e6b6b 100644
> --- a/include/media/media-device.h
> +++ b/include/media/media-device.h
> @@ -23,6 +23,7 @@
> #ifndef _MEDIA_DEVICE_H
> #define _MEDIA_DEVICE_H
>
> +#include <linux/kref.h>
> #include <linux/list.h>
> #include <linux/mutex.h>
>
> @@ -283,6 +284,7 @@ struct media_entity_notify {
> * struct media_device - Media device
> * @dev: Parent device
> * @devnode: Media device node
> + * @kref: Object refcount
> * @driver_name: Optional device driver name. If not set, calls to
> * %MEDIA_IOC_DEVICE_INFO will return dev->driver->name.
> * This is needed for USB drivers for example, as otherwise
> @@ -347,6 +349,7 @@ struct media_device {
> /* dev->driver_data points to this struct. */
> struct device *dev;
> struct media_devnode devnode;
> + struct kref kref;
>
> char model[32];
> char driver_name[32];
>
--
Shuah Khan
Sr. Linux Kernel Developer
Open Source Innovation Group
Samsung Research America (Silicon Valley)
shuahkh@xxxxxxxxxxxxxxx | (970) 217-8978
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