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ldev->lock is used to serialize lag change operations. Since multiport eswtich functionality was added, we now change the mode dynamically. However, acquiring ldev->lock is not allowed as it could possibly lead to a deadlock as reported by the lockdep mechanism. [ 836.154963] WARNING: possible circular locking dependency detected [ 836.155850] 5.19.0-rc5_net_56b7df2 #1 Not tainted [ 836.156549] ------------------------------------------------------ [ 836.157418] handler1/12198 is trying to acquire lock: [ 836.158178] ffff888187d52b58 (&ldev->lock){+.+.}-{3:3}, at: mlx5_lag_do_mirred+0x3b/0x70 [mlx5_core] [ 836.159575] [ 836.159575] but task is already holding lock: [ 836.160474] ffff8881d4de2930 (&block->cb_lock){++++}-{3:3}, at: tc_setup_cb_add+0x5b/0x200 [ 836.161669] which lock already depends on the new lock. [ 836.162905] [ 836.162905] the existing dependency chain (in reverse order) is: [ 836.164008] -> #3 (&block->cb_lock){++++}-{3:3}: [ 836.164946] down_write+0x25/0x60 [ 836.165548] tcf_block_get_ext+0x1c6/0x5d0 [ 836.166253] ingress_init+0x74/0xa0 [sch_ingress] [ 836.167028] qdisc_create.constprop.0+0x130/0x5e0 [ 836.167805] tc_modify_qdisc+0x481/0x9f0 [ 836.168490] rtnetlink_rcv_msg+0x16e/0x5a0 [ 836.169189] netlink_rcv_skb+0x4e/0xf0 [ 836.169861] netlink_unicast+0x190/0x250 [ 836.170543] netlink_sendmsg+0x243/0x4b0 [ 836.171226] sock_sendmsg+0x33/0x40 [ 836.171860] ____sys_sendmsg+0x1d1/0x1f0 [ 836.172535] ___sys_sendmsg+0xab/0xf0 [ 836.173183] __sys_sendmsg+0x51/0x90 [ 836.173836] do_syscall_64+0x3d/0x90 [ 836.174471] entry_SYSCALL_64_after_hwframe+0x46/0xb0 [ 836.175282] [ 836.175282] -> #2 (rtnl_mutex){+.+.}-{3:3}: [ 836.176190] __mutex_lock+0x6b/0xf80 [ 836.176830] register_netdevice_notifier+0x21/0x120 [ 836.177631] rtnetlink_init+0x2d/0x1e9 [ 836.178289] netlink_proto_init+0x163/0x179 [ 836.178994] do_one_initcall+0x63/0x300 [ 836.179672] kernel_init_freeable+0x2cb/0x31b [ 836.180403] kernel_init+0x17/0x140 [ 836.181035] ret_from_fork+0x1f/0x30 [ 836.181687] -> #1 (pernet_ops_rwsem){+.+.}-{3:3}: [ 836.182628] down_write+0x25/0x60 [ 836.183235] unregister_netdevice_notifier+0x1c/0xb0 [ 836.184029] mlx5_ib_roce_cleanup+0x94/0x120 [mlx5_ib] [ 836.184855] __mlx5_ib_remove+0x35/0x60 [mlx5_ib] [ 836.185637] mlx5_eswitch_unregister_vport_reps+0x22f/0x440 [mlx5_core] [ 836.186698] auxiliary_bus_remove+0x18/0x30 [ 836.187409] device_release_driver_internal+0x1f6/0x270 [ 836.188253] bus_remove_device+0xef/0x160 [ 836.188939] device_del+0x18b/0x3f0 [ 836.189562] mlx5_rescan_drivers_locked+0xd6/0x2d0 [mlx5_core] [ 836.190516] mlx5_lag_remove_devices+0x69/0xe0 [mlx5_core] [ 836.191414] mlx5_do_bond_work+0x441/0x620 [mlx5_core] [ 836.192278] process_one_work+0x25c/0x590 [ 836.192963] worker_thread+0x4f/0x3d0 [ 836.193609] kthread+0xcb/0xf0 [ 836.194189] ret_from_fork+0x1f/0x30 [ 836.194826] -> #0 (&ldev->lock){+.+.}-{3:3}: [ 836.195734] __lock_acquire+0x15b8/0x2a10 [ 836.196426] lock_acquire+0xce/0x2d0 [ 836.197057] __mutex_lock+0x6b/0xf80 [ 836.197708] mlx5_lag_do_mirred+0x3b/0x70 [mlx5_core] [ 836.198575] tc_act_parse_mirred+0x25b/0x800 [mlx5_core] [ 836.199467] parse_tc_actions+0x168/0x5a0 [mlx5_core] [ 836.200340] __mlx5e_add_fdb_flow+0x263/0x480 [mlx5_core] [ 836.201241] mlx5e_configure_flower+0x8a0/0x1820 [mlx5_core] [ 836.202187] tc_setup_cb_add+0xd7/0x200 [ 836.202856] fl_hw_replace_filter+0x14c/0x1f0 [cls_flower] [ 836.203739] fl_change+0xbbe/0x1730 [cls_flower] [ 836.204501] tc_new_tfilter+0x407/0xd90 [ 836.205168] rtnetlink_rcv_msg+0x406/0x5a0 [ 836.205877] netlink_rcv_skb+0x4e/0xf0 [ 836.206535] netlink_unicast+0x190/0x250 [ 836.207217] netlink_sendmsg+0x243/0x4b0 [ 836.207915] sock_sendmsg+0x33/0x40 [ 836.208538] ____sys_sendmsg+0x1d1/0x1f0 [ 836.209219] ___sys_sendmsg+0xab/0xf0 [ 836.209878] __sys_sendmsg+0x51/0x90 [ 836.210510] do_syscall_64+0x3d/0x90 [ 836.211137] entry_SYSCALL_64_after_hwframe+0x46/0xb0 [ 836.211954] other info that might help us debug this: [ 836.213174] Chain exists of: [ 836.213174] &ldev->lock --> rtnl_mutex --> &block->cb_lock 836.214650] Possible unsafe locking scenario: [ 836.214650] [ 836.215574] CPU0 CPU1 [ 836.216255] ---- ---- [ 836.216943] lock(&block->cb_lock); [ 836.217518] lock(rtnl_mutex); [ 836.218348] lock(&block->cb_lock); [ 836.219212] lock(&ldev->lock); [ 836.219758] [ 836.219758] *** DEADLOCK *** [ 836.219758] [ 836.220747] 2 locks held by handler1/12198: [ 836.221390] #0: ffff8881d4de2930 (&block->cb_lock){++++}-{3:3}, at: tc_setup_cb_add+0x5b/0x200 [ 836.222646] #1: ffff88810c9a92c0 (&esw->mode_lock){++++}-{3:3}, at: mlx5_esw_hold+0x39/0x50 [mlx5_core] [ 836.224063] stack backtrace: [ 836.224799] CPU: 6 PID: 12198 Comm: handler1 Not tainted 5.19.0-rc5_net_56b7df2 #1 [ 836.225923] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 [ 836.227476] Call Trace: [ 836.227929] <TASK> [ 836.228332] dump_stack_lvl+0x57/0x7d [ 836.228924] check_noncircular+0x104/0x120 [ 836.229562] __lock_acquire+0x15b8/0x2a10 [ 836.230201] lock_acquire+0xce/0x2d0 [ 836.230776] ? mlx5_lag_do_mirred+0x3b/0x70 [mlx5_core] [ 836.231614] ? find_held_lock+0x2b/0x80 [ 836.232221] __mutex_lock+0x6b/0xf80 [ 836.232799] ? mlx5_lag_do_mirred+0x3b/0x70 [mlx5_core] [ 836.233636] ? mlx5_lag_do_mirred+0x3b/0x70 [mlx5_core] [ 836.234451] ? xa_load+0xc3/0x190 [ 836.234995] mlx5_lag_do_mirred+0x3b/0x70 [mlx5_core] [ 836.235803] tc_act_parse_mirred+0x25b/0x800 [mlx5_core] [ 836.236636] ? tc_act_can_offload_mirred+0x135/0x210 [mlx5_core] [ 836.237550] parse_tc_actions+0x168/0x5a0 [mlx5_core] [ 836.238364] __mlx5e_add_fdb_flow+0x263/0x480 [mlx5_core] [ 836.239202] mlx5e_configure_flower+0x8a0/0x1820 [mlx5_core] [ 836.240076] ? lock_acquire+0xce/0x2d0 [ 836.240668] ? tc_setup_cb_add+0x5b/0x200 [ 836.241294] tc_setup_cb_add+0xd7/0x200 [ 836.241917] fl_hw_replace_filter+0x14c/0x1f0 [cls_flower] [ 836.242709] fl_change+0xbbe/0x1730 [cls_flower] [ 836.243408] tc_new_tfilter+0x407/0xd90 [ 836.244043] ? tc_del_tfilter+0x880/0x880 [ 836.244672] rtnetlink_rcv_msg+0x406/0x5a0 [ 836.245310] ? netlink_deliver_tap+0x7a/0x4b0 [ 836.245991] ? if_nlmsg_stats_size+0x2b0/0x2b0 [ 836.246675] netlink_rcv_skb+0x4e/0xf0 [ 836.258046] netlink_unicast+0x190/0x250 [ 836.258669] netlink_sendmsg+0x243/0x4b0 [ 836.259288] sock_sendmsg+0x33/0x40 [ 836.259857] ____sys_sendmsg+0x1d1/0x1f0 [ 836.260473] ___sys_sendmsg+0xab/0xf0 [ 836.261064] ? lock_acquire+0xce/0x2d0 [ 836.261669] ? find_held_lock+0x2b/0x80 [ 836.262272] ? __fget_files+0xb9/0x190 [ 836.262871] ? __fget_files+0xd3/0x190 [ 836.263462] __sys_sendmsg+0x51/0x90 [ 836.264064] do_syscall_64+0x3d/0x90 [ 836.264652] entry_SYSCALL_64_after_hwframe+0x46/0xb0 [ 836.265425] RIP: 0033:0x7fdbe5e2677d [ 836.266012] Code: 28 89 54 24 1c 48 89 74 24 10 89 7c 24 08 e8 ba ee ff ff 8b 54 24 1c 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 33 44 89 c7 48 89 44 24 08 e8 ee ee ff ff 48 [ 836.268485] RSP: 002b:00007fdbe48a75a0 EFLAGS: 00000293 ORIG_RAX: 000000000000002e [ 836.269598] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fdbe5e2677d [ 836.270576] RDX: 0000000000000000 RSI: 00007fdbe48a7640 RDI: 000000000000003c [ 836.271565] RBP: 00007fdbe48a8368 R08: 0000000000000000 R09: 0000000000000000 [ 836.272546] R10: 00007fdbe48a84b0 R11: 0000000000000293 R12: 0000557bd17dc860 [ 836.273527] R13: 0000000000000000 R14: 0000557bd17dc860 R15: 00007fdbe48a7640 [ 836.274521] </TASK> To avoid using mode holding ldev->lock in the configure flow, we queue a work to the lag workqueue and cease wait on a completion object. In addition, we remove the lock from mlx5_lag_do_mirred() since it is not really protecting anything. It should be noted that an actual deadlock has not been observed. Signed-off-by: Eli Cohen <elic@nvidia.com> Reviewed-by: Mark Bloch <mbloch@nvidia.com> Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Linux kernel
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