net/mlx5: devcom, expose locked variant of send_event

Factor mlx5_devcom_send_event() into two functions:
- mlx5_devcom_locked_send_event(): performs the dispatch (and
  rollback) with comp->sem already held by the caller.
- mlx5_devcom_send_event(): unchanged wrapper that takes comp->sem,
  calls the locked variant, and releases it.

This lets callers bracket multiple event broadcasts under a single
held write lock, eliminating the gap between consecutive dispatches
where peer state could change.

Will be used by a downstream patch.

Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20260612113904.537595-3-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 25 insertions, 7 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/devcom.c b/drivers/net/ethernet/mellanox/mlx5/core/lib/devcom.c
index d40c53193ea8..96b4f06d6184 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lib/devcom.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/devcom.c
@@ -287,9 +287,9 @@ int mlx5_devcom_comp_get_size(struct mlx5_devcom_comp_dev *devcom)
 	return kref_read(&comp->ref);
 }
 
-int mlx5_devcom_send_event(struct mlx5_devcom_comp_dev *devcom,
-			   int event, int rollback_event,
-			   void *event_data)
+int mlx5_devcom_locked_send_event(struct mlx5_devcom_comp_dev *devcom,
+				  int event, int rollback_event,
+				  void *event_data)
 {
 	struct mlx5_devcom_comp_dev *pos;
 	struct mlx5_devcom_comp *comp;
@@ -299,8 +299,8 @@ int mlx5_devcom_send_event(struct mlx5_devcom_comp_dev *devcom,
 	if (!devcom)
 		return -ENODEV;
 
+	lockdep_assert_held_write(&devcom->comp->sem);
 	comp = devcom->comp;
-	down_write(&comp->sem);
 	list_for_each_entry(pos, &comp->comp_dev_list_head, list) {
 		data = rcu_dereference_protected(pos->data, lockdep_is_held(&comp->sem));
 
@@ -311,12 +311,11 @@ int mlx5_devcom_send_event(struct mlx5_devcom_comp_dev *devcom,
 		}
 	}
 
-	up_write(&comp->sem);
 	return 0;
 
 rollback:
 	if (list_entry_is_head(pos, &comp->comp_dev_list_head, list))
-		goto out;
+		return err;
 	pos = list_prev_entry(pos, list);
 	list_for_each_entry_from_reverse(pos, &comp->comp_dev_list_head, list) {
 		data = rcu_dereference_protected(pos->data, lockdep_is_held(&comp->sem));
@@ -324,7 +323,23 @@ rollback:
 		if (pos != devcom && data)
 			comp->handler(rollback_event, data, event_data);
 	}
-out:
+	return err;
+}
+
+int mlx5_devcom_send_event(struct mlx5_devcom_comp_dev *devcom,
+			   int event, int rollback_event,
+			   void *event_data)
+{
+	struct mlx5_devcom_comp *comp;
+	int err;
+
+	if (!devcom)
+		return -ENODEV;
+
+	comp = devcom->comp;
+	down_write(&comp->sem);
+	err = mlx5_devcom_locked_send_event(devcom, event, rollback_event,
+					    event_data);
 	up_write(&comp->sem);
 	return err;
 }
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/devcom.h b/drivers/net/ethernet/mellanox/mlx5/core/lib/devcom.h
index 316052a85ca5..d5c60c03e55c 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lib/devcom.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/devcom.h
@@ -46,6 +46,9 @@ mlx5_devcom_register_component(struct mlx5_devcom_dev *devc,
 			       void *data);
 void mlx5_devcom_unregister_component(struct mlx5_devcom_comp_dev *devcom);
 
+int mlx5_devcom_locked_send_event(struct mlx5_devcom_comp_dev *devcom,
+				  int event, int rollback_event,
+				  void *event_data);
 int mlx5_devcom_send_event(struct mlx5_devcom_comp_dev *devcom,
 			   int event, int rollback_event,
 			   void *event_data);