[PATCH iwl-net 4/6] ice: don't block on locks in ice_tear_down_devlink_rate_tree()

@@ -20,7 +20,7 @@ void ice_devlink_init_regions(struct ice_pf *pf);
 void ice_devlink_destroy_regions(struct ice_pf *pf);
 
 int ice_devlink_rate_init_tx_topology(struct devlink *devlink, struct ice_vsi *vsi);
-void ice_tear_down_devlink_rate_tree(struct ice_pf *pf);
+int ice_tear_down_devlink_rate_tree(struct ice_pf *pf);
 void ice_devlink_rate_clear_tx_topology(struct ice_vsi *vsi);
 
 #endif /* _ICE_DEVLINK_H_ */

@@ -20,6 +20,7 @@ u8 ice_dcb_get_num_tc(struct ice_dcbx_cfg *dcbcfg);
 void ice_vsi_set_dcb_tc_cfg(struct ice_vsi *vsi);
 bool ice_is_pfc_causing_hung_q(struct ice_pf *pf, unsigned int txqueue);
 u8 ice_dcb_get_tc(struct ice_vsi *vsi, int queue_index);
+int ice_dcb_prep_multi_tc(struct ice_pf *pf);
 int
 ice_pf_dcb_cfg(struct ice_pf *pf, struct ice_dcbx_cfg *new_cfg, bool locked);
 int ice_dcb_bwchk(struct ice_pf *pf, struct ice_dcbx_cfg *dcbcfg);

@@ -683,31 +683,68 @@ static int ice_devlink_tx_sched_layers_validate(struct devlink *devlink, u32 id,
 	return 0;
 }
 
+static bool ice_devlink_rate_tree_is_exported(struct ice_port_info *pi)
+{
+	struct ice_sched_node *tc_node;
+	bool exported = false;
+
+	if (pi->port_state != ICE_SCHED_PORT_STATE_READY)
+		return false;
+
+	mutex_lock(&pi->sched_lock);
+	tc_node = pi->root->children[0];
+	for (int i = 0; i < tc_node->num_children; i++) {
+		if (tc_node->children[i]->rate_node) {
+			exported = true;
+			break;
+		}
+	}
+	mutex_unlock(&pi->sched_lock);
+
+	return exported;
+}
+
 /**
  * ice_tear_down_devlink_rate_tree - removes devlink-rate exported tree
  * @pf: pf struct
  *
  * This function tears down tree exported during VF's creation.
+ *
+ * Return: 0 on success or when no tree is exported, -EAGAIN if a lock could
+ * not be taken.
  */
-void ice_tear_down_devlink_rate_tree(struct ice_pf *pf)
+int ice_tear_down_devlink_rate_tree(struct ice_pf *pf)
 {
 	struct devlink *devlink;
 	struct ice_vf *vf;
 	unsigned int bkt;
 
+	/* The tree is exported only when switchdev is running */
+	if (!ice_is_switchdev_running(pf) ||
+	    !ice_devlink_rate_tree_is_exported(pf->hw.port_info))
+		return 0;
+
+	ASSERT_RTNL();
+
 	devlink = priv_to_devlink(pf);
 
-	devl_lock(devlink);
-	mutex_lock(&pf->vfs.table_lock);
+	/* Both locks are taken before RTNL elsewhere, so only try them here */
+	if (!mutex_trylock(&pf->vfs.table_lock))
+		return -EAGAIN;
+	if (!devl_trylock(devlink)) {
+		mutex_unlock(&pf->vfs.table_lock);
+		return -EAGAIN;
+	}
 	ice_for_each_vf(pf, bkt, vf) {
 		if (vf->devlink_port.devlink_rate)
 			devl_rate_leaf_destroy(&vf->devlink_port);
 	}
-	mutex_unlock(&pf->vfs.table_lock);
-
 	ice_devlink_rate_clear_tx_topology(ice_get_main_vsi(pf));
 	devl_rate_nodes_destroy(devlink);
 	devl_unlock(devlink);
+	mutex_unlock(&pf->vfs.table_lock);
+
+	return 0;
 }
 
 /**

@@ -341,6 +341,23 @@ int ice_dcb_bwchk(struct ice_pf *pf, struct ice_dcbx_cfg *dcbcfg)
 	return 0;
 }
 
+/**
+ * ice_dcb_prep_multi_tc - prepare the Tx scheduler for more than one TC
+ * @pf: pointer to the PF struct
+ *
+ * Return: 0 on success, -EBUSY if the Tx scheduler is customized via
+ * devlink-rate, -EAGAIN if its devlink-rate export could not be torn down.
+ */
+int ice_dcb_prep_multi_tc(struct ice_pf *pf)
+{
+	if (pf->hw.port_info->is_custom_tx_enabled) {
+		dev_err(ice_pf_to_dev(pf), "Custom Tx scheduler feature enabled, can't configure DCB\n");
+		return -EBUSY;
+	}
+
+	return ice_tear_down_devlink_rate_tree(pf);
+}
+
 /**
  * ice_pf_dcb_cfg - Apply new DCB configuration
  * @pf: pointer to the PF struct

@@ -364,12 +381,12 @@ int ice_pf_dcb_cfg(struct ice_pf *pf, struct ice_dcbx_cfg *new_cfg, bool locked)
 
 	/* Enable DCB tagging only when more than one TC */
 	if (ice_dcb_get_num_tc(new_cfg) > 1) {
+		int err;
+
 		dev_dbg(dev, "DCB tagging enabled (num TC > 1)\n");
-		if (pf->hw.port_info->is_custom_tx_enabled) {
-			dev_err(dev, "Custom Tx scheduler feature enabled, can't configure DCB\n");
-			return -EBUSY;
-		}
-		ice_tear_down_devlink_rate_tree(pf);
+		err = ice_dcb_prep_multi_tc(pf);
+		if (err)
+			return err;
 
 		set_bit(ICE_FLAG_DCB_ENA, pf->flags);
 	} else {

@@ -736,6 +736,7 @@ static int ice_dcbnl_setapp(struct net_device *netdev, struct dcb_app *app)
 	struct ice_pf *pf = ice_netdev_to_pf(netdev);
 	struct ice_dcb_app_priority_table new_app;
 	struct ice_dcbx_cfg *old_cfg, *new_cfg;
+	int tc_to_prep;
 	u8 max_tc;
 	int ret;
 

@@ -779,6 +780,18 @@ static int ice_dcbnl_setapp(struct net_device *netdev, struct dcb_app *app)
 	new_cfg = &pf->hw.port_info->qos_cfg.desired_dcbx_cfg;
 	old_cfg = &pf->hw.port_info->qos_cfg.local_dcbx_cfg;
 
+	/* fail before any change; switching to DSCP mode enables max_tc TCs */
+	if (old_cfg->pfc_mode == ICE_QOS_MODE_VLAN)
+		tc_to_prep = max_tc;
+	else
+		tc_to_prep = ice_dcb_get_num_tc(new_cfg);
+
+	if (tc_to_prep > 1) {
+		ret = ice_dcb_prep_multi_tc(pf);
+		if (ret)
+			goto setapp_out;
+	}
+
 	ret = dcb_ieee_setapp(netdev, app);
 	if (ret)
 		goto setapp_out;

@@ -850,7 +863,7 @@ static int ice_dcbnl_setapp(struct net_device *netdev, struct dcb_app *app)
 	/* return of zero indicates new cfg applied */
 	if (ret == ICE_DCB_HW_CHG_RST)
 		ice_dcbnl_devreset(netdev);
-	else
+	else if (ret > 0)
 		ret = ICE_DCB_NO_HW_CHG;
 
 setapp_out:

@@ -9180,7 +9180,9 @@ static int ice_setup_tc_mqprio_qdisc(struct net_device *netdev, void *type_data)
 			dev_err(dev, "Custom Tx scheduler feature enabled, can't configure ADQ\n");
 			return -EBUSY;
 		}
-		ice_tear_down_devlink_rate_tree(pf);
+		ret = ice_tear_down_devlink_rate_tree(pf);
+		if (ret)
+			return ret;
 
 		ret = ice_validate_mqprio_qopt(vsi, mqprio_qopt);
 		if (ret) {