On 3/13/24 08:24, Sakari Ailus wrote:
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@xxxxxxxxxxxxxxx>
Reviewed-by: Julien Massot <julien.massot@xxxxxxxxxxxxx>
---
drivers/media/v4l2-core/v4l2-subdev.c | 12 +++-----
include/media/v4l2-subdev.h | 40 +++++++++++++++++++++++++++
2 files changed, 44 insertions(+), 8 deletions(-)
diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 4c6198c48dd6..6c34df19ea2f 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -1400,17 +1400,13 @@ 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;
}
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index a9e6b8146279..9cce48365975 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -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
--
Julien Massot
Senior Software Engineer
Collabora Ltd.
Platinum Building, St John's Innovation Park, Cambridge CB4 0DS, UK
Registered in England & Wales, no. 5513718
