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Mon, 16 Mar 2026 02:46:32 -0700 From: Tariq Toukan To: Eric Dumazet , Jakub Kicinski , Paolo Abeni , Andrew Lunn , "David S. Miller" CC: Saeed Mahameed , Leon Romanovsky , Tariq Toukan , Mark Bloch , , , , Gal Pressman , Moshe Shemesh , Dragos Tatulea , Cosmin Ratiu Subject: [PATCH net 1/3] net/mlx5: qos: Restrict RTNL area to avoid a lock cycle Date: Mon, 16 Mar 2026 11:46:01 +0200 Message-ID: <20260316094603.6999-2-tariqt@nvidia.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20260316094603.6999-1-tariqt@nvidia.com> References: <20260316094603.6999-1-tariqt@nvidia.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN3PEPF0000B06A:EE_|CH3PR12MB8659:EE_ X-MS-Office365-Filtering-Correlation-Id: 6fe7e4a6-f6cb-4520-dde9-08de8340f2d0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|36860700016|1800799024|376014|22082099003|56012099003|18002099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.118.232;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge1.nvidia.com;CAT:NONE;SFS:(13230040)(82310400026)(36860700016)(1800799024)(376014)(22082099003)(56012099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: Rka54KdIG7Ws0zZGWs+uGHvNhsI6+d5HyfKAVY4FCN72y83u2ahp21h3IiM4MzqgDGV/psxbd1wk2Ku4p1snkMd6GW1u+M26sC351uomc6OCS72uEv/24WpOOQCP9+SzNUe5OmERNIT2NpLjsEIjjhaKm0f0kKNkR/nbXrvNguEGISEw5FQ2CcfvL3ELViIM4k9YU5OkRAE6DfBdQbia/wIUDoJBCu3Nlo23naMfVJZ6rFPtnLKISKe35d1WvmGtApDw5eMs8m1bU1SpEmEgE373e7qFGsTQSuZq0/0TtoBt2sj3m+W5WVBD1jnBT1HW4VauhQ0JTrXZlxKA0hhZKFsfaDl65MEUNvQmkexSX1dWd7uY2MSMJAbtxoSOH78IB9FZerj9QoeILOmbqY2uTXF+7N2jTdRDFMZmGh3bmY8kXiJFe6eubqnOmaV48wyz X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Mar 2026 09:46:50.6085 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 6fe7e4a6-f6cb-4520-dde9-08de8340f2d0 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN3PEPF0000B06A.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB8659 From: Cosmin Ratiu A lock dependency cycle exists where: 1. mlx5_ib_roce_init -> mlx5_core_uplink_netdev_event_replay -> mlx5_blocking_notifier_call_chain (takes notifier_rwsem) -> mlx5e_mdev_notifier_event -> mlx5_netdev_notifier_register -> register_netdevice_notifier_dev_net (takes rtnl) => notifier_rwsem -> rtnl 2. mlx5e_probe -> _mlx5e_probe -> mlx5_core_uplink_netdev_set (takes uplink_netdev_lock) -> mlx5_blocking_notifier_call_chain (takes notifier_rwsem) => uplink_netdev_lock -> notifier_rwsem 3: devlink_nl_rate_set_doit -> devlink_nl_rate_set -> mlx5_esw_devlink_rate_leaf_tx_max_set -> esw_qos_devlink_rate_to_mbps -> mlx5_esw_qos_max_link_speed_get (takes rtnl) -> mlx5_esw_qos_lag_link_speed_get_locked -> mlx5_uplink_netdev_get (takes uplink_netdev_lock) => rtnl -> uplink_netdev_lock => BOOM! (lock cycle) Fix that by restricting the rtnl-protected section to just the necessary part, the call to netdev_master_upper_dev_get and speed querying, so that the last lock dependency is avoided and the cycle doesn't close. This is safe because mlx5_uplink_netdev_get uses netdev_hold to keep the uplink netdev alive while its master device is queried. Use this opportunity to rename the ambiguously-named "hold_rtnl_lock" argument to "take_rtnl" and remove the "_locked" suffix from mlx5_esw_qos_lag_link_speed_get_locked. Fixes: 6b4be64fd9fe ("net/mlx5e: Harden uplink netdev access against device unbind") Signed-off-by: Cosmin Ratiu Reviewed-by: Dragos Tatulea Signed-off-by: Tariq Toukan --- .../net/ethernet/mellanox/mlx5/core/esw/qos.c | 23 ++++++++----------- 1 file changed, 9 insertions(+), 14 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/esw/qos.c b/drivers/net/ethernet/mellanox/mlx5/core/esw/qos.c index 26178d0bac92..faccc60fc93a 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/esw/qos.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/esw/qos.c @@ -1489,24 +1489,24 @@ static int esw_qos_node_enable_tc_arbitration(struct mlx5_esw_sched_node *node, return err; } -static u32 mlx5_esw_qos_lag_link_speed_get_locked(struct mlx5_core_dev *mdev) +static u32 mlx5_esw_qos_lag_link_speed_get(struct mlx5_core_dev *mdev, + bool take_rtnl) { struct ethtool_link_ksettings lksettings; struct net_device *slave, *master; u32 speed = SPEED_UNKNOWN; - /* Lock ensures a stable reference to master and slave netdevice - * while port speed of master is queried. - */ - ASSERT_RTNL(); - slave = mlx5_uplink_netdev_get(mdev); if (!slave) goto out; + if (take_rtnl) + rtnl_lock(); master = netdev_master_upper_dev_get(slave); if (master && !__ethtool_get_link_ksettings(master, &lksettings)) speed = lksettings.base.speed; + if (take_rtnl) + rtnl_unlock(); out: mlx5_uplink_netdev_put(mdev, slave); @@ -1514,20 +1514,15 @@ static u32 mlx5_esw_qos_lag_link_speed_get_locked(struct mlx5_core_dev *mdev) } static int mlx5_esw_qos_max_link_speed_get(struct mlx5_core_dev *mdev, u32 *link_speed_max, - bool hold_rtnl_lock, struct netlink_ext_ack *extack) + bool take_rtnl, + struct netlink_ext_ack *extack) { int err; if (!mlx5_lag_is_active(mdev)) goto skip_lag; - if (hold_rtnl_lock) - rtnl_lock(); - - *link_speed_max = mlx5_esw_qos_lag_link_speed_get_locked(mdev); - - if (hold_rtnl_lock) - rtnl_unlock(); + *link_speed_max = mlx5_esw_qos_lag_link_speed_get(mdev, take_rtnl); if (*link_speed_max != (u32)SPEED_UNKNOWN) return 0; -- 2.44.0