On Wednesday 16 Mar 2016 09:04:02 Mauro Carvalho Chehab wrote:
> Right now, the lock schema for media_device struct is messy,
> since sometimes, it is protected via a spin lock, while, for
> media graph traversal, it is protected by a mutex.
>
> Solve this conflict by always using a mutex.
>
> As a side effect, this prevents a bug where the media notifiers
> were called at atomic context.
And as a side effect the kernel now deadlocks in MEDIA_IOC_ENUM_LINKS. I'm all
for fixing messy the lock schema, but maybe you should test patches before
merging them ?
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx>
> ---
> drivers/media/media-device.c | 32 ++++++++++++++------------------
> drivers/media/media-entity.c | 16 ++++++++--------
> include/media/media-device.h | 6 +-----
> 3 files changed, 23 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
> index 6e43c95629ea..c32fa15cc76e 100644
> --- a/drivers/media/media-device.c
> +++ b/drivers/media/media-device.c
> @@ -90,17 +90,17 @@ static struct media_entity *find_entity(struct
> media_device *mdev, u32 id)
>
> id &= ~MEDIA_ENT_ID_FLAG_NEXT;
>
> - spin_lock(&mdev->lock);
> + mutex_lock(&mdev->graph_mutex);
>
> media_device_for_each_entity(entity, mdev) {
> if (((media_entity_id(entity) == id) && !next) ||
> ((media_entity_id(entity) > id) && next)) {
> - spin_unlock(&mdev->lock);
> + mutex_unlock(&mdev->graph_mutex);
> return entity;
> }
> }
>
> - spin_unlock(&mdev->lock);
> + mutex_unlock(&mdev->graph_mutex);
>
> return NULL;
> }
> @@ -590,12 +590,12 @@ int __must_check media_device_register_entity(struct
> media_device *mdev, if (!ida_pre_get(&mdev->entity_internal_idx,
> GFP_KERNEL))
> return -ENOMEM;
>
> - spin_lock(&mdev->lock);
> + mutex_lock(&mdev->graph_mutex);
>
> ret = ida_get_new_above(&mdev->entity_internal_idx, 1,
> &entity->internal_idx);
> if (ret < 0) {
> - spin_unlock(&mdev->lock);
> + mutex_unlock(&mdev->graph_mutex);
> return ret;
> }
>
> @@ -615,9 +615,6 @@ int __must_check media_device_register_entity(struct
> media_device *mdev, (notify)->notify(entity, notify->notify_data);
> }
>
> - spin_unlock(&mdev->lock);
> -
> - mutex_lock(&mdev->graph_mutex);
> if (mdev->entity_internal_idx_max
>
> >= mdev->pm_count_walk.ent_enum.idx_max) {
>
> struct media_entity_graph new = { .top = 0 };
> @@ -680,9 +677,9 @@ void media_device_unregister_entity(struct media_entity
> *entity) if (mdev == NULL)
> return;
>
> - spin_lock(&mdev->lock);
> + mutex_lock(&mdev->graph_mutex);
> __media_device_unregister_entity(entity);
> - spin_unlock(&mdev->lock);
> + mutex_unlock(&mdev->graph_mutex);
> }
> EXPORT_SYMBOL_GPL(media_device_unregister_entity);
>
> @@ -703,7 +700,6 @@ void media_device_init(struct media_device *mdev)
> INIT_LIST_HEAD(&mdev->pads);
> INIT_LIST_HEAD(&mdev->links);
> INIT_LIST_HEAD(&mdev->entity_notify);
> - spin_lock_init(&mdev->lock);
> mutex_init(&mdev->graph_mutex);
> ida_init(&mdev->entity_internal_idx);
>
> @@ -752,9 +748,9 @@ EXPORT_SYMBOL_GPL(__media_device_register);
> int __must_check media_device_register_entity_notify(struct media_device
> *mdev, struct media_entity_notify *nptr)
> {
> - spin_lock(&mdev->lock);
> + mutex_lock(&mdev->graph_mutex);
> list_add_tail(&nptr->list, &mdev->entity_notify);
> - spin_unlock(&mdev->lock);
> + mutex_unlock(&mdev->graph_mutex);
> return 0;
> }
> EXPORT_SYMBOL_GPL(media_device_register_entity_notify);
> @@ -771,9 +767,9 @@ static void
> __media_device_unregister_entity_notify(struct media_device *mdev, void
> media_device_unregister_entity_notify(struct media_device *mdev, struct
> media_entity_notify *nptr)
> {
> - spin_lock(&mdev->lock);
> + mutex_lock(&mdev->graph_mutex);
> __media_device_unregister_entity_notify(mdev, nptr);
> - spin_unlock(&mdev->lock);
> + mutex_unlock(&mdev->graph_mutex);
> }
> EXPORT_SYMBOL_GPL(media_device_unregister_entity_notify);
>
> @@ -787,11 +783,11 @@ void media_device_unregister(struct media_device
> *mdev) if (mdev == NULL)
> return;
>
> - spin_lock(&mdev->lock);
> + mutex_lock(&mdev->graph_mutex);
>
> /* Check if mdev was ever registered at all */
> if (!media_devnode_is_registered(&mdev->devnode)) {
> - spin_unlock(&mdev->lock);
> + mutex_unlock(&mdev->graph_mutex);
> return;
> }
>
> @@ -811,7 +807,7 @@ void media_device_unregister(struct media_device *mdev)
> kfree(intf);
> }
>
> - spin_unlock(&mdev->lock);
> + mutex_unlock(&mdev->graph_mutex);
>
> device_remove_file(&mdev->devnode.dev, &dev_attr_model);
> media_devnode_unregister(&mdev->devnode);
> diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c
> index e95070b3a3d4..c53c1d5589a0 100644
> --- a/drivers/media/media-entity.c
> +++ b/drivers/media/media-entity.c
> @@ -219,7 +219,7 @@ int media_entity_pads_init(struct media_entity *entity,
> u16 num_pads, entity->pads = pads;
>
> if (mdev)
> - spin_lock(&mdev->lock);
> + mutex_lock(&mdev->graph_mutex);
>
> for (i = 0; i < num_pads; i++) {
> pads[i].entity = entity;
> @@ -230,7 +230,7 @@ int media_entity_pads_init(struct media_entity *entity,
> u16 num_pads, }
>
> if (mdev)
> - spin_unlock(&mdev->lock);
> + mutex_unlock(&mdev->graph_mutex);
>
> return 0;
> }
> @@ -747,9 +747,9 @@ void media_entity_remove_links(struct media_entity
> *entity) if (mdev == NULL)
> return;
>
> - spin_lock(&mdev->lock);
> + mutex_lock(&mdev->graph_mutex);
> __media_entity_remove_links(entity);
> - spin_unlock(&mdev->lock);
> + mutex_unlock(&mdev->graph_mutex);
> }
> EXPORT_SYMBOL_GPL(media_entity_remove_links);
>
> @@ -951,9 +951,9 @@ void media_remove_intf_link(struct media_link *link)
> if (mdev == NULL)
> return;
>
> - spin_lock(&mdev->lock);
> + mutex_lock(&mdev->graph_mutex);
> __media_remove_intf_link(link);
> - spin_unlock(&mdev->lock);
> + mutex_unlock(&mdev->graph_mutex);
> }
> EXPORT_SYMBOL_GPL(media_remove_intf_link);
>
> @@ -975,8 +975,8 @@ void media_remove_intf_links(struct media_interface
> *intf) if (mdev == NULL)
> return;
>
> - spin_lock(&mdev->lock);
> + mutex_lock(&mdev->graph_mutex);
> __media_remove_intf_links(intf);
> - spin_unlock(&mdev->lock);
> + mutex_unlock(&mdev->graph_mutex);
> }
> EXPORT_SYMBOL_GPL(media_remove_intf_links);
> diff --git a/include/media/media-device.h b/include/media/media-device.h
> index df74cfa7da4a..0c2de97181f3 100644
> --- a/include/media/media-device.h
> +++ b/include/media/media-device.h
> @@ -25,7 +25,6 @@
>
> #include <linux/list.h>
> #include <linux/mutex.h>
> -#include <linux/spinlock.h>
>
> #include <media/media-devnode.h>
> #include <media/media-entity.h>
> @@ -304,8 +303,7 @@ struct media_entity_notify {
> * @pads: List of registered pads
> * @links: List of registered links
> * @entity_notify: List of registered entity_notify callbacks
> - * @lock: Entities list lock
> - * @graph_mutex: Entities graph operation lock
> + * @graph_mutex: Protects access to struct media_device data
> * @pm_count_walk: Graph walk for power state walk. Access serialised using
> * graph_mutex.
> *
> @@ -371,8 +369,6 @@ struct media_device {
> /* notify callback list invoked when a new entity is registered */
> struct list_head entity_notify;
>
> - /* Protects the graph objects creation/removal */
> - spinlock_t lock;
> /* Serializes graph operations. */
> struct mutex graph_mutex;
> struct media_entity_graph pm_count_walk;
--
Regards,
Laurent Pinchart
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