Hi Tomi,
Thank you for the patch.
On Wed, Feb 16, 2022 at 03:00:46PM +0200, Tomi Valkeinen wrote:
> The V4L2 subdevs have managed without centralized locking for the state
> (previously pad_config), as the try-state is supposedly safe (although I
> believe two TRY ioctls for the same fd would race), and the
> active-state, and its locking, is managed by the drivers internally.
>
> We now have active-state in a centralized position, and need locking.
> Strictly speaking the locking is only needed for new drivers that use
> the new state, as the current drivers continue behaving as they used to.
>
> However, active-state locking is complicated by the fact that currently
> the real active-state of a subdev is split into multiple parts: the new
> v4l2_subdev_state, subdev control state, and subdev's internal state.
>
> In the future all these three states should be combined into one state
> (the v4l2_subdev_state), and then a single lock for the state should be
> sufficient.
>
> But to solve the current split-state situation we need to share locks
> between the three states. This is accomplished by using the same lock
> management as the control handler does: we use a pointer to a mutex,
> allowing the driver to override the default mutex. Thus the driver can
> do e.g.:
>
> sd->state_lock = sd->ctrl_handler->lock;
>
> before calling v4l2_subdev_init_finalize(), resulting in sharing the
> same lock between the states and the controls.
>
> The locking model for active-state is such that any subdev op that gets
> the state as a parameter expects the state to be already locked by the
> caller, and expects the caller to release the lock.
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
> drivers/media/platform/rcar-vin/rcar-v4l2.c | 3 +-
> drivers/media/platform/vsp1/vsp1_entity.c | 4 +-
> drivers/media/v4l2-core/v4l2-subdev.c | 78 +++++++++++++++----
> drivers/staging/media/tegra-video/vi.c | 4 +-
> include/media/v4l2-subdev.h | 85 ++++++++++++++++++++-
> 5 files changed, 155 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/media/platform/rcar-vin/rcar-v4l2.c b/drivers/media/platform/rcar-vin/rcar-v4l2.c
> index da88f968c31a..3759f4619a77 100644
> --- a/drivers/media/platform/rcar-vin/rcar-v4l2.c
> +++ b/drivers/media/platform/rcar-vin/rcar-v4l2.c
> @@ -255,6 +255,7 @@ static int rvin_try_format(struct rvin_dev *vin, u32 which,
> {
> struct v4l2_subdev *sd = vin_to_source(vin);
> struct v4l2_subdev_state *sd_state;
> + static struct lock_class_key key;
> struct v4l2_subdev_format format = {
> .which = which,
> .pad = vin->parallel.source_pad,
> @@ -267,7 +268,7 @@ static int rvin_try_format(struct rvin_dev *vin, u32 which,
> * FIXME: Drop this call, drivers are not supposed to use
> * __v4l2_subdev_state_alloc().
> */
> - sd_state = __v4l2_subdev_state_alloc(sd);
> + sd_state = __v4l2_subdev_state_alloc(sd, "rvin:state->lock", &key);
> if (IS_ERR(sd_state))
> return PTR_ERR(sd_state);
>
> diff --git a/drivers/media/platform/vsp1/vsp1_entity.c b/drivers/media/platform/vsp1/vsp1_entity.c
> index c82b3fb7b89a..a116a3362f9e 100644
> --- a/drivers/media/platform/vsp1/vsp1_entity.c
> +++ b/drivers/media/platform/vsp1/vsp1_entity.c
> @@ -613,6 +613,7 @@ int vsp1_entity_init(struct vsp1_device *vsp1, struct vsp1_entity *entity,
> const char *name, unsigned int num_pads,
> const struct v4l2_subdev_ops *ops, u32 function)
> {
> + static struct lock_class_key key;
> struct v4l2_subdev *subdev;
> unsigned int i;
> int ret;
> @@ -679,7 +680,8 @@ int vsp1_entity_init(struct vsp1_device *vsp1, struct vsp1_entity *entity,
> * FIXME: Drop this call, drivers are not supposed to use
> * __v4l2_subdev_state_alloc().
> */
> - entity->config = __v4l2_subdev_state_alloc(&entity->subdev);
> + entity->config = __v4l2_subdev_state_alloc(&entity->subdev,
> + "vsp1:config->lock", &key);
> if (IS_ERR(entity->config)) {
> media_entity_cleanup(&entity->subdev.entity);
> return PTR_ERR(entity->config);
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index b67bbce82612..0df9bbe1819d 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -27,8 +27,9 @@
> static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
> {
> struct v4l2_subdev_state *state;
> + static struct lock_class_key key;
>
> - state = __v4l2_subdev_state_alloc(sd);
> + state = __v4l2_subdev_state_alloc(sd, "fh->state->lock", &key);
> if (IS_ERR(state))
> return PTR_ERR(state);
>
> @@ -383,18 +384,15 @@ subdev_ioctl_get_state(struct v4l2_subdev *sd, struct v4l2_subdev_fh *subdev_fh,
> v4l2_subdev_get_active_state(sd);
> }
>
> -static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> +static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
> + struct v4l2_subdev_state *state)
> {
> struct video_device *vdev = video_devdata(file);
> struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
> struct v4l2_fh *vfh = file->private_data;
> - struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
> bool ro_subdev = test_bit(V4L2_FL_SUBDEV_RO_DEVNODE, &vdev->flags);
> - struct v4l2_subdev_state *state;
> int rval;
>
> - state = subdev_ioctl_get_state(sd, subdev_fh, cmd, arg);
> -
> switch (cmd) {
> case VIDIOC_SUBDEV_QUERYCAP: {
> struct v4l2_subdev_capability *cap = arg;
> @@ -707,8 +705,24 @@ static long subdev_do_ioctl_lock(struct file *file, unsigned int cmd, void *arg)
>
> if (lock && mutex_lock_interruptible(lock))
> return -ERESTARTSYS;
> - if (video_is_registered(vdev))
> - ret = subdev_do_ioctl(file, cmd, arg);
> +
> + if (video_is_registered(vdev)) {
> + struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
> + struct v4l2_fh *vfh = file->private_data;
> + struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
> + struct v4l2_subdev_state *state;
> +
> + state = subdev_ioctl_get_state(sd, subdev_fh, cmd, arg);
> +
> + if (state)
> + v4l2_subdev_lock_state(state);
> +
> + ret = subdev_do_ioctl(file, cmd, arg, state);
> +
> + if (state)
> + v4l2_subdev_unlock_state(state);
> + }
> +
> if (lock)
> mutex_unlock(lock);
> return ret;
> @@ -864,7 +878,7 @@ v4l2_subdev_link_validate_get_format(struct media_pad *pad,
> media_entity_to_v4l2_subdev(pad->entity);
> struct v4l2_subdev_state *state;
>
> - state = v4l2_subdev_get_active_state(sd);
> + state = v4l2_subdev_get_locked_active_state(sd);
>
> fmt->which = V4L2_SUBDEV_FORMAT_ACTIVE;
> fmt->pad = pad->index;
> @@ -906,7 +920,9 @@ int v4l2_subdev_link_validate(struct media_link *link)
> }
> EXPORT_SYMBOL_GPL(v4l2_subdev_link_validate);
>
> -struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd)
> +struct v4l2_subdev_state *
> +__v4l2_subdev_state_alloc(struct v4l2_subdev *sd, const char *lock_name,
> + struct lock_class_key *lock_key)
> {
> struct v4l2_subdev_state *state;
> int ret;
> @@ -915,6 +931,12 @@ struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd)
> if (!state)
> return ERR_PTR(-ENOMEM);
>
> + __mutex_init(&state->_lock, lock_name, lock_key);
> + if (sd->state_lock)
> + state->lock = sd->state_lock;
> + else
> + state->lock = &state->_lock;
> +
> if (sd->entity.num_pads) {
> state->pads = kvmalloc_array(sd->entity.num_pads,
> sizeof(*state->pads),
> @@ -925,7 +947,14 @@ struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd)
> }
> }
>
> + /*
> + * There can be no race at this point, but we lock the state anyway to
> + * satisfy lockdep checks.
> + */
> + v4l2_subdev_lock_state(state);
> ret = v4l2_subdev_call(sd, pad, init_cfg, state);
> + v4l2_subdev_unlock_state(state);
> +
> if (ret < 0 && ret != -ENOIOCTLCMD)
> goto err;
>
> @@ -946,16 +975,19 @@ void __v4l2_subdev_state_free(struct v4l2_subdev_state *state)
> if (!state)
> return;
>
> + mutex_destroy(&state->_lock);
> +
> kvfree(state->pads);
> kfree(state);
> }
> EXPORT_SYMBOL_GPL(__v4l2_subdev_state_free);
>
> -int v4l2_subdev_init_finalize(struct v4l2_subdev *sd)
> +int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
> + struct lock_class_key *key)
> {
> struct v4l2_subdev_state *state;
>
> - state = __v4l2_subdev_state_alloc(sd);
> + state = __v4l2_subdev_state_alloc(sd, name, key);
> if (IS_ERR(state))
> return PTR_ERR(state);
>
> @@ -963,7 +995,7 @@ int v4l2_subdev_init_finalize(struct v4l2_subdev *sd)
>
> return 0;
> }
> -EXPORT_SYMBOL_GPL(v4l2_subdev_init_finalize);
> +EXPORT_SYMBOL_GPL(__v4l2_subdev_init_finalize);
>
> void v4l2_subdev_cleanup(struct v4l2_subdev *sd)
> {
> @@ -972,6 +1004,26 @@ void v4l2_subdev_cleanup(struct v4l2_subdev *sd)
> }
> EXPORT_SYMBOL_GPL(v4l2_subdev_cleanup);
>
> +struct v4l2_subdev_state *v4l2_subdev_lock_active_state(struct v4l2_subdev *sd)
> +{
> + mutex_lock(sd->active_state->lock);
> +
> + return sd->active_state;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_subdev_lock_active_state);
> +
> +void v4l2_subdev_lock_state(struct v4l2_subdev_state *state)
> +{
> + mutex_lock(state->lock);
> +}
> +EXPORT_SYMBOL_GPL(v4l2_subdev_lock_state);
> +
> +void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state)
> +{
> + mutex_unlock(state->lock);
> +}
> +EXPORT_SYMBOL_GPL(v4l2_subdev_unlock_state);
> +
> #endif /* CONFIG_MEDIA_CONTROLLER */
>
> void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops)
> diff --git a/drivers/staging/media/tegra-video/vi.c b/drivers/staging/media/tegra-video/vi.c
> index 07d368f345cd..8e184aa4c252 100644
> --- a/drivers/staging/media/tegra-video/vi.c
> +++ b/drivers/staging/media/tegra-video/vi.c
> @@ -491,6 +491,7 @@ static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
> struct v4l2_pix_format *pix)
> {
> const struct tegra_video_format *fmtinfo;
> + static struct lock_class_key key;
> struct v4l2_subdev *subdev;
> struct v4l2_subdev_format fmt;
> struct v4l2_subdev_state *sd_state;
> @@ -511,7 +512,8 @@ static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
> * FIXME: Drop this call, drivers are not supposed to use
> * __v4l2_subdev_state_alloc().
> */
> - sd_state = __v4l2_subdev_state_alloc(subdev);
> + sd_state = __v4l2_subdev_state_alloc(subdev, "tegra:state->lock",
> + &key);
> if (IS_ERR(sd_state))
> return PTR_ERR(sd_state);
> /*
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index 1bbe4383966c..8d089a2dbd32 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -658,6 +658,8 @@ struct v4l2_subdev_pad_config {
> /**
> * struct v4l2_subdev_state - Used for storing subdev state information.
> *
> + * @_lock: default for 'lock'
> + * @lock: mutex for the state. May be replaced by the user.
> * @pads: &struct v4l2_subdev_pad_config array
> *
> * This structure only needs to be passed to the pad op if the 'which' field
> @@ -665,6 +667,9 @@ struct v4l2_subdev_pad_config {
> * %V4L2_SUBDEV_FORMAT_ACTIVE it is safe to pass %NULL.
> */
> struct v4l2_subdev_state {
> + /* lock for the struct v4l2_subdev_state fields */
> + struct mutex _lock;
> + struct mutex *lock;
> struct v4l2_subdev_pad_config *pads;
> };
>
> @@ -888,6 +893,9 @@ struct v4l2_subdev_platform_data {
> * @subdev_notifier: A sub-device notifier implicitly registered for the sub-
> * device using v4l2_async_register_subdev_sensor().
> * @pdata: common part of subdevice platform data
> + * @state_lock: A pointer to a lock used for all the subdev's states, set by the
> + * driver. This is optional. If NULL, each state instance will get
> + * a lock of its own.
> * @active_state: Active state for the subdev (NULL for subdevs tracking the
> * state internally). Initialized by calling
> * v4l2_subdev_init_finalize().
> @@ -922,6 +930,7 @@ struct v4l2_subdev {
> struct v4l2_async_notifier *notifier;
> struct v4l2_async_notifier *subdev_notifier;
> struct v4l2_subdev_platform_data *pdata;
> + struct mutex *state_lock;
>
> /*
> * The fields below are private, and should only be accessed via
> @@ -1144,12 +1153,16 @@ int v4l2_subdev_link_validate(struct media_link *link);
> * __v4l2_subdev_state_alloc - allocate v4l2_subdev_state
> *
> * @sd: pointer to &struct v4l2_subdev for which the state is being allocated.
> + * @lock_name: name of the state lock
> + * @key: lock_class_key for the lock
> *
> * Must call __v4l2_subdev_state_free() when state is no longer needed.
> *
> * Not to be called directly by the drivers.
> */
> -struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd);
> +struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd,
> + const char *lock_name,
> + struct lock_class_key *key);
>
> /**
> * __v4l2_subdev_state_free - free a v4l2_subdev_state
> @@ -1174,7 +1187,16 @@ void __v4l2_subdev_state_free(struct v4l2_subdev_state *state);
> *
> * The user must call v4l2_subdev_cleanup() when the subdev is being removed.
> */
> -int v4l2_subdev_init_finalize(struct v4l2_subdev *sd);
> +#define v4l2_subdev_init_finalize(sd) \
> + ({ \
> + static struct lock_class_key __key; \
> + const char *name = KBUILD_BASENAME \
> + ":" __stringify(__LINE__) ":sd->active_state->lock"; \
> + __v4l2_subdev_init_finalize(sd, name, &__key); \
> + })
> +
> +int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
> + struct lock_class_key *key);
>
> /**
> * v4l2_subdev_cleanup() - Releases the resources allocated by the subdevice
> @@ -1191,14 +1213,71 @@ void v4l2_subdev_cleanup(struct v4l2_subdev *sd);
> * @sd: The subdevice
> *
> * Returns the active state for the subdevice, or NULL if the subdev does not
> - * support active state.
> + * support active state. If the state is not NULL, calls
> + * lockdep_assert_not_held() to issue a warning if the state is locked.
> + *
> + * This function is to be used e.g. when getting the active state for the sole
> + * purpose of passing it forward, without accessing the state fields.
> */
> static inline struct v4l2_subdev_state *
> v4l2_subdev_get_active_state(struct v4l2_subdev *sd)
> {
> + if (sd->active_state)
> + lockdep_assert_not_held(sd->active_state->lock);
> + return sd->active_state;
> +}
> +
> +/**
> + * v4l2_subdev_get_locked_active_state() - Checks that the active subdev state
> + * is locked and returns it
> + *
> + * @sd: The subdevice
> + *
> + * Returns the active state for the subdevice, or NULL if the subdev does not
> + * support active state. If the state is not NULL, calls lockdep_assert_held()
> + * to issue a warning if the state is not locked.
> + *
> + * This function is to be used when the caller knows that the active state is
> + * already locked.
> + */
> +static inline struct v4l2_subdev_state *
> +v4l2_subdev_get_locked_active_state(struct v4l2_subdev *sd)
> +{
> + if (sd->active_state)
> + lockdep_assert_held(sd->active_state->lock);
> return sd->active_state;
> }
>
> +/**
> + * v4l2_subdev_lock_active_state() - Locks and returns the active subdev state
> + * for the subdevice
> + * @sd: The subdevice
> + *
> + * Returns the locked active state for the subdevice, or NULL if the subdev
> + * does not support active state.
> + *
> + * The state must be unlocked with v4l2_subdev_unlock_state() after use.
> + */
> +struct v4l2_subdev_state *v4l2_subdev_lock_active_state(struct v4l2_subdev *sd);
> +
> +/**
> + * v4l2_subdev_lock_state() - Locks the subdev state
> + * @state: The subdevice state
> + *
> + * Locks the given subdev state.
> + *
> + * The state must be unlocked with v4l2_subdev_unlock_state() after use.
> + */
> +void v4l2_subdev_lock_state(struct v4l2_subdev_state *state);
> +
> +/**
> + * v4l2_subdev_unlock_state() - Unlocks the subdev state
> + * @state: The subdevice state
> + *
> + * Unlocks the given subdev state.
> + */
> +void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state);
> +
> #endif /* CONFIG_MEDIA_CONTROLLER */
>
> /**
--
Regards,
Laurent Pinchart
