On 04/06/2016 03:55 PM, 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 when the media notifiers
> is called at atomic context, while running the notifier callback:
>
> BUG: sleeping function called from invalid context at mm/slub.c:1289
> in_atomic(): 1, irqs_disabled(): 0, pid: 3479, name: modprobe
> 4 locks held by modprobe/3479:
> #0: (&dev->mutex){......}, at: [<ffffffff81ce8933>] __driver_attach+0xa3/0x160
> #1: (&dev->mutex){......}, at: [<ffffffff81ce8941>] __driver_attach+0xb1/0x160
> #2: (register_mutex#5){+.+.+.}, at: [<ffffffffa10596c7>] usb_audio_probe+0x257/0x1c90 [snd_usb_audio]
> #3: (&(&mdev->lock)->rlock){+.+.+.}, at: [<ffffffffa0e6051b>] media_device_register_entity+0x1cb/0x700 [media]
> CPU: 2 PID: 3479 Comm: modprobe Not tainted 4.5.0-rc3+ #49
> Hardware name: /NUC5i7RYB, BIOS RYBDWi35.86A.0350.2015.0812.1722 08/12/2015
> 0000000000000000 ffff8803b3f6f288 ffffffff81933901 ffff8803c4bae000
> ffff8803c4bae5c8 ffff8803b3f6f2b0 ffffffff811c6af5 ffff8803c4bae000
> ffffffff8285d7f6 0000000000000509 ffff8803b3f6f2f0 ffffffff811c6ce5
> Call Trace:
> [<ffffffff81933901>] dump_stack+0x85/0xc4
> [<ffffffff811c6af5>] ___might_sleep+0x245/0x3a0
> [<ffffffff811c6ce5>] __might_sleep+0x95/0x1a0
> [<ffffffff8155aade>] kmem_cache_alloc_trace+0x20e/0x300
> [<ffffffffa0e66e3d>] ? media_add_link+0x4d/0x140 [media]
> [<ffffffffa0e66e3d>] media_add_link+0x4d/0x140 [media]
> [<ffffffffa0e69931>] media_create_pad_link+0xa1/0x600 [media]
> [<ffffffffa0fe11b3>] au0828_media_graph_notify+0x173/0x360 [au0828]
> [<ffffffffa0e68a6a>] ? media_gobj_create+0x1ba/0x480 [media]
> [<ffffffffa0e606fb>] media_device_register_entity+0x3ab/0x700 [media]
>
> Reviewed-by: Javier Martinez Canillas <javier@xxxxxxxxxxxxxxx>
> Acked-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx>
Acked-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Regards,
Hans
> ---
> drivers/media/media-device.c | 39 +++++++++++++--------------------------
> drivers/media/media-entity.c | 16 ++++++++--------
> include/media/media-device.h | 6 +-----
> 3 files changed, 22 insertions(+), 39 deletions(-)
>
> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
> index 6e43c95629ea..898a3cf814ba 100644
> --- a/drivers/media/media-device.c
> +++ b/drivers/media/media-device.c
> @@ -90,18 +90,13 @@ static struct media_entity *find_entity(struct media_device *mdev, u32 id)
>
> id &= ~MEDIA_ENT_ID_FLAG_NEXT;
>
> - spin_lock(&mdev->lock);
> -
> media_device_for_each_entity(entity, mdev) {
> if (((media_entity_id(entity) == id) && !next) ||
> ((media_entity_id(entity) > id) && next)) {
> - spin_unlock(&mdev->lock);
> return entity;
> }
> }
>
> - spin_unlock(&mdev->lock);
> -
> return NULL;
> }
>
> @@ -431,6 +426,7 @@ static long media_device_ioctl(struct file *filp, unsigned int cmd,
> struct media_device *dev = to_media_device(devnode);
> long ret;
>
> + mutex_lock(&dev->graph_mutex);
> switch (cmd) {
> case MEDIA_IOC_DEVICE_INFO:
> ret = media_device_get_info(dev,
> @@ -443,29 +439,24 @@ static long media_device_ioctl(struct file *filp, unsigned int cmd,
> break;
>
> case MEDIA_IOC_ENUM_LINKS:
> - mutex_lock(&dev->graph_mutex);
> ret = media_device_enum_links(dev,
> (struct media_links_enum __user *)arg);
> - mutex_unlock(&dev->graph_mutex);
> break;
>
> case MEDIA_IOC_SETUP_LINK:
> - mutex_lock(&dev->graph_mutex);
> ret = media_device_setup_link(dev,
> (struct media_link_desc __user *)arg);
> - mutex_unlock(&dev->graph_mutex);
> break;
>
> case MEDIA_IOC_G_TOPOLOGY:
> - mutex_lock(&dev->graph_mutex);
> ret = media_device_get_topology(dev,
> (struct media_v2_topology __user *)arg);
> - mutex_unlock(&dev->graph_mutex);
> break;
>
> default:
> ret = -ENOIOCTLCMD;
> }
> + mutex_unlock(&dev->graph_mutex);
>
> return ret;
> }
> @@ -590,12 +581,12 @@ 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 +606,6 @@ 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 +668,9 @@ 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 +691,6 @@ 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 +739,9 @@ 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 +758,9 @@ 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 +774,11 @@ 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 +798,7 @@ 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 07809f698464..b21ef244ad3e 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;
>
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