On 03/22/2016 01:56 PM, Shuah Khan wrote:
> 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>
>
Acked the wrong patch. Sorry. Will ack the v2 which is the one I tested.
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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