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media: v4l: subdev: Add a function to lock two sub-device states, use it

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Add two new functions, v4l2_subdev_lock_states() and
v4l2_subdev_unclock_states(), to acquire and release the state of two
sub-devices. They differ from calling v4l2_subdev_{un,}lock_state() so
that if the two states share the same lock, the lock is acquired only
once.

Also use the new functions in v4l2_subdev_link_validate().

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Julien Massot <julien.massot@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
This commit is contained in:
Sakari Ailus 2023-09-06 10:56:14 +03:00 committed by Hans Verkuil
parent cd2c75454d
commit 72364b91ce
2 changed files with 44 additions and 8 deletions
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12
drivers/media/v4l2-core/v4l2-subdev.c
View file

@ -1437,17 +1437,13 @@ int v4l2_subdev_link_validate(struct media_link *link)
states_locked = sink_state && source_state;
if (states_locked) {
v4l2_subdev_lock_state(sink_state);
v4l2_subdev_lock_state(source_state);
}
if (states_locked)
v4l2_subdev_lock_states(sink_state, source_state);
ret = v4l2_subdev_link_validate_locked(link, states_locked);
if (states_locked) {
v4l2_subdev_unlock_state(sink_state);
v4l2_subdev_unlock_state(source_state);
}
if (states_locked)
v4l2_subdev_unlock_states(sink_state, source_state);
return ret;
}

40
include/media/v4l2-subdev.h
View file

@ -1724,6 +1724,46 @@ static inline void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state)
mutex_unlock(state->lock);
}
/**
* v4l2_subdev_lock_states - Lock two sub-device states
* @state1: One subdevice state
* @state2: The other subdevice state
*
* Locks the state of two sub-devices.
*
* The states must be unlocked with v4l2_subdev_unlock_states() after use.
*
* This differs from calling v4l2_subdev_lock_state() on both states so that if
* the states share the same lock, the lock is acquired only once (so no
* deadlock occurs). The caller is responsible for ensuring the locks will
* always be acquired in the same order.
*/
static inline void v4l2_subdev_lock_states(struct v4l2_subdev_state *state1,
struct v4l2_subdev_state *state2)
{
mutex_lock(state1->lock);
if (state1->lock != state2->lock)
mutex_lock(state2->lock);
}
/**
* v4l2_subdev_unlock_states() - Unlock two sub-device states
* @state1: One subdevice state
* @state2: The other subdevice state
*
* Unlocks the state of two sub-devices.
*
* This differs from calling v4l2_subdev_unlock_state() on both states so that
* if the states share the same lock, the lock is released only once.
*/
static inline void v4l2_subdev_unlock_states(struct v4l2_subdev_state *state1,
struct v4l2_subdev_state *state2)
{
mutex_unlock(state1->lock);
if (state1->lock != state2->lock)
mutex_unlock(state2->lock);
}
/**
* v4l2_subdev_get_unlocked_active_state() - Checks that the active subdev state
* is unlocked and returns it