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Miller" , Eric Dumazet , Jakub Kicinski , , Paolo Abeni CC: Akiva Goldberger , Gal Pressman , Leon Romanovsky , open list , , Mark Bloch , Saeed Mahameed , Shay Drory , Simon Horman , Tariq Toukan Subject: [PATCH net] net/mlx5: Fix lock dependency cycle on uplink unbind in switchdev mode Date: Thu, 15 Oct 2026 12:34:19 +0300 Message-ID: <20261015093419.1150837-1-tariqt@nvidia.com> X-Mailer: git-send-email 2.44.0 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: BN1PEPF00018547:EE_|CHBPR12MB319464:EE_ X-MS-Office365-Filtering-Correlation-Id: d7b912b4-4ea3-496c-72e6-08df2a9f8ebf X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|1800799024|7416014|36860700016|82310400026|23010399003|56012099006|11063799006|261009223327099003|261009221227099003|261009220027099003|261009221727099003|261009223027099003|10067099003|18002099003|13003099007; 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)(376014)(1800799024)(7416014)(36860700016)(82310400026)(23010399003)(56012099006)(11063799006)(261009223327099003)(261009221227099003)(261009220027099003)(261009221727099003)(261009223027099003)(10067099003)(18002099003)(13003099007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: RhGnl9X1ATg6bb54JQ/owK/y53gFZjjSPTCgzKec8IderJm4NPDc770zUgTPp6YELi07/SEBc5EqLeXciwe31CetpAflKelKpi+0hO8X2PdbgYCbl9Ui3yypdgZErqLiisRnN66nGYaWDBrZMggbH/eGSfbnUVLqMRorFvVvsdVKB24ZcIU/Sr/rPttzbrzyZ2/x5nGzYF3hYrlxwXPCT5CYfdJHEVXLmiTwVddUHHHATIDoKiAb0ehFdtuRpLMZinNwZyS7Bj+ySwNNYshZBLJE9h1R4M61n9RMC8D+Q6IfDXDcchq6LT2MmIFil46Pn0yEIwq++g5kTNeGgwXmWOh2wfS5BSIyWUnWzoeoBQ93L2PkHacKPvSJC40zH41fYrwm2/2/0jgQS2opaMlT6nTMhUjpCEOOcnbaco1f8eOXahWM7oB6fSxV3uqVUTYI X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Oct 2026 09:34:49.1033 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d7b912b4-4ea3-496c-72e6-08df2a9f8ebf 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: BN1PEPF00018547.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CHBPR12MB319464 From: Shay Drory mlx5_eswitch_safe_aux_devs_remove() holds esw->mode_lock for read across mlx5_core_reps_aux_devs_remove(), which unregisters the REPs auxiliary devices and therefore takes esw->offloads.reps_lock. This nests mode_lock outside reps_lock, the exact nesting mlx5_devlink_eswitch_mode_set() goes out of its way to avoid: there the eswitch_operation_in_progress flag is raised, mode_lock is dropped, and only then is reps_lock taken. With that nesting in place lockdep reports a cycle [1]. IPsec packet offload takes mode_lock under ipsec->tx_esw->ft.mutex, through mlx5_eswitch_block_encap() in tx_get(); the mode change path takes rtnl_mutex under reps_lock, through the netns immutable set; and unregistering a REP netdev takes ft.mutex, through the xfrm policy flush, under the netdev instance lock which is itself nested under rtnl_mutex: &ipsec->tx_esw->ft.mutex -> &esw->mode_lock -> &esw->offloads.reps_lock -> rtnl_mutex -> &dev_instance_lock_key -> &ipsec->tx_esw->ft.mutex Reproduced by unbinding the uplink ETH driver with an IPsec packet offload policy configured in switchdev mode: devlink dev eswitch set pci/0000:08:00.0 mode switchdev echo 2 > /sys/class/net/eth2/device/sriov_numvfs ip addr add 193.237.171.21/16 dev eth2 ip link set eth2 up ip xfrm policy add src 193.237.171.21 dst 193.237.172.22 \ offload packet dev eth2 dir out \ tmpl src 193.237.171.21/16 dst 193.237.172.22/16 \ proto esp reqid 0xdcd95f7b mode transport priority 21 echo mlx5_core.eth.0 > /sys/bus/auxiliary/drivers/mlx5_core.eth/unbind Keep mode_lock and reps_lock unnested here as well: take mode_lock for write, raise eswitch_operation_in_progress, drop mode_lock, remove the REPs auxiliary devices, then retake mode_lock and clear the flag. The flag keeps excluding concurrent mode transitions and mode users while mode_lock is not held. Acquiring mode_lock for write can't go through mlx5_esw_try_lock(), which also refuses the lock while esw->user_count is non zero: that count is held for the lifetime of every offloaded TC flow, and those flows are only flushed by the REP netdev unregister this function is about to perform. Use a local trylock helper that attempts to acquire mode_lock and only bails if the operation flag is set. Bail out early when the device has no eswitch, which mlx5_esw_hold() used to cover. [1] WARNING: possible circular locking dependency detected 7.2.0-rc2+ #2 Tainted: G W ------------------------------------------------------ run.sh/7007 is trying to acquire lock: (&ipsec->tx_esw->ft.mutex){+.+.}-{4:4}, at: tx_ft_put_policy+0x81/0x130 [mlx5_core] but task is already holding lock: (&dev_instance_lock_key#9){+.+.}-{4:4}, at: unregister_netdevice_many_notify+0x3eb/0x2140 which lock already depends on the new lock. [...] Chain exists of: &ipsec->tx_esw->ft.mutex --> rtnl_mutex --> &dev_instance_lock_key#9 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&dev_instance_lock_key#9); lock(rtnl_mutex); lock(&dev_instance_lock_key#9); lock(&ipsec->tx_esw->ft.mutex); *** DEADLOCK *** 8 locks held by run.sh/7007: [...] #3: (&esw->mode_lock){++++}-{4:4}, at: mlx5_esw_hold+0xcc/0x150 [mlx5_core] #4: (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0xa5/0x560 #5: (&esw->offloads.reps_lock){+.+.}-{4:4}, at: mlx5_eswitch_unregister_vport_reps+0x1f/0x40 [mlx5_core] #6: (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_dev_lock+0xde/0x260 #7: (&dev_instance_lock_key#9){+.+.}-{4:4}, at: unregister_netdevice_many_notify+0x3eb/0x2140 Call Trace: tx_ft_put_policy+0x81/0x130 [mlx5_core] mlx5e_xfrm_del_policy+0x36/0x90 [mlx5_core] xfrm_policy_kill+0xc3/0x410 xfrm_dev_policy_flush+0x258/0x360 xfrm_dev_event+0x2a3/0x3b0 notifier_call_chain+0x97/0x2b0 netif_close_many+0x367/0x710 netif_close_many_and_unlock+0x1d/0x240 unregister_netdevice_many_notify+0x567/0x2140 unregister_netdevice_queue+0x29a/0x350 unregister_netdev+0x18/0x60 mlx5e_vport_rep_unload+0x20b/0x2b0 [mlx5_core] mlx5_eswitch_unregister_vport_reps_blocked+0xb0/0x230 [mlx5_core] mlx5_eswitch_unregister_vport_reps+0x2a/0x40 [mlx5_core] device_release_driver_internal+0x3b2/0x560 bus_remove_device+0x2a9/0x510 device_del+0x3b9/0x990 mlx5_core_reps_aux_devs_remove+0x135/0x200 [mlx5_core] mlx5_eswitch_safe_aux_devs_remove+0xa5/0xd0 [mlx5_core] mlx5e_remove+0x10d/0x370 [mlx5_core] device_release_driver_internal+0x3b2/0x560 unbind_store+0xce/0xf0 kernfs_fop_write_iter+0x3c6/0x5d0 vfs_write+0x4d9/0xf70 ksys_write+0xec/0x1c0 do_syscall_64+0xaf/0x5c0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 Fixes: 2ae8c7edea87 ("net/mlx5: Fix Unbinding uplink-netdev in switchdev mode") Signed-off-by: Shay Drory Reviewed-by: Mark Bloch Reviewed-by: Akiva Goldberger Signed-off-by: Tariq Toukan --- .../mellanox/mlx5/core/eswitch_offloads.c | 37 +++++++++++++++++-- 1 file changed, 34 insertions(+), 3 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c b/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c index eb74b6260168..f934cb2b26b0 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c @@ -4438,15 +4438,36 @@ static bool mlx5_devlink_switchdev_active_mode_change(struct mlx5_eswitch *esw, #define MLX5_ESW_HOLD_TIMEOUT_MS 7000 #define MLX5_ESW_HOLD_RETRY_DELAY_MS 500 +/* Unlike mlx5_esw_try_lock(), don't refuse the lock over eswitch users. + * Teardown must run even with TC flows still offloaded, as those are only + * flushed once the REPs are removed. + */ +static bool esw_try_lock_ignore_users(struct mlx5_eswitch *esw) +{ + if (!down_write_trylock(&esw->mode_lock)) + return false; + + if (esw->eswitch_operation_in_progress) { + up_write(&esw->mode_lock); + return false; + } + + return true; +} + void mlx5_eswitch_safe_aux_devs_remove(struct mlx5_core_dev *dev) { + struct mlx5_eswitch *esw = dev->priv.eswitch; unsigned long timeout; bool hold_esw = true; + if (!mlx5_esw_allowed(esw)) + return; + /* Wait for any concurrent eswitch mode transition to complete. */ - if (!mlx5_esw_hold(dev)) { + if (!esw_try_lock_ignore_users(esw)) { timeout = jiffies + msecs_to_jiffies(MLX5_ESW_HOLD_TIMEOUT_MS); - while (!mlx5_esw_hold(dev)) { + while (!esw_try_lock_ignore_users(esw)) { if (!time_before(jiffies, timeout)) { hold_esw = false; break; @@ -4455,9 +4476,19 @@ void mlx5_eswitch_safe_aux_devs_remove(struct mlx5_core_dev *dev) } } if (hold_esw) { + /* Keep mode_lock and reps_lock unnested. The operation flag + * excludes mode users while mode_lock is dropped before the + * REPs removal takes reps_lock. + */ + esw->eswitch_operation_in_progress = true; + mlx5_esw_unlock(esw); + if (mlx5_eswitch_mode(dev) == MLX5_ESWITCH_OFFLOADS) mlx5_core_reps_aux_devs_remove(dev); - mlx5_esw_release(dev); + + down_write(&esw->mode_lock); + esw->eswitch_operation_in_progress = false; + mlx5_esw_unlock(esw); } } base-commit: 513444cc62e231a11c9b15ea88de0890da9b2b4f -- 2.44.0