From 96ff396e6e0eb754b73f1870ef7e72f2f80cdbe0 Mon Sep 17 00:00:00 2001 From: Mika Westerberg Date: Fri, 15 May 2026 10:28:40 +0300 Subject: thunderbolt: Use separate lock class for each ring When connected to another host and then unplugging cable lockdep triggers following: ====================================================== WARNING: possible circular locking dependency detected 7.1.0-rc2+ #1775 Tainted: G U ------------------------------------------------------ kworker/u16:6/312 is trying to acquire lock: ffff8881179c70a8 ((work_completion)(&ring->work)){+.+.}-{0:0}, at: __flush_work+0x3cf/0xd10 but task is already holding lock: ffff8881a8b810b0 (&net->connection_lock){+.+.}-{4:4}, at: tbnet_tear_down+0x110/0x720 [thunderbolt_net] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&net->connection_lock){+.+.}-{4:4}: __mutex_lock+0x19a/0x2490 mutex_lock_nested+0x1b/0x30 tbnet_handle_packet+0x74c/0xd70 [thunderbolt_net] tb_xdomain_handle_request+0x37c/0x4b0 [thunderbolt] tb_domain_event_cb+0xc9/0x140 [thunderbolt] tb_ctl_handle_event+0xd6/0x2c0 [thunderbolt] tb_ctl_rx_callback+0x22c/0xa10 [thunderbolt] ring_work+0x715/0xcb0 [thunderbolt] process_one_work+0x902/0x1790 worker_thread+0x5cd/0xfe0 kthread+0x339/0x420 ret_from_fork+0x79a/0x9d0 ret_from_fork_asm+0x1a/0x30 -> #0 ((work_completion)(&ring->work)){+.+.}-{0:0}: __lock_acquire+0x1592/0x2640 lock_acquire+0x1a3/0x300 __flush_work+0x3e9/0xd10 flush_work+0x21/0x30 tb_ring_stop+0x240/0x840 [thunderbolt] tbnet_tear_down+0x2ff/0x720 [thunderbolt_net] tbnet_stop+0x47/0x1a0 [thunderbolt_net] __dev_close_many+0x19e/0x4e0 netif_close_many+0x1e8/0x640 unregister_netdevice_many_notify+0x6d3/0x22d0 unregister_netdevice_queue+0x2b9/0x3a0 unregister_netdev+0x1c/0x70 tbnet_remove+0x52/0xb0 [thunderbolt_net] tb_service_remove+0x8a/0xe0 [thunderbolt] device_remove+0xc5/0x190 device_release_driver_internal+0x3db/0x590 device_release_driver+0x12/0x20 bus_remove_device+0x2c1/0x580 device_del+0x3d9/0x9f0 device_unregister+0x17/0xc0 unregister_service+0x46/0x60 [thunderbolt] device_for_each_child_reverse+0xfa/0x180 tb_xdomain_unregister+0x57/0xe0 [thunderbolt] unregister_unplugged_xdomain+0x101/0x1a0 [thunderbolt] bus_for_each_dev+0x111/0x1a0 tb_domain_unregister_unplugged_xdomains+0x98/0xe0 [thunderbolt] tb_handle_hotplug+0xc3/0x2bb0 [thunderbolt] process_one_work+0x902/0x1790 worker_thread+0x5cd/0xfe0 kthread+0x339/0x420 ret_from_fork+0x79a/0x9d0 ret_from_fork_asm+0x1a/0x30 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&net->connection_lock); lock((work_completion)(&ring->work)); lock(&net->connection_lock); lock((work_completion)(&ring->work)); This in fact is false positive because they involve unrelated rings (and unrelated work structures). In the first one it is ring 0 which is used for control traffic and in the second it is dealing with another ring used for the high-speed traffic. Fix this by using separate lock class for each ring worker. Signed-off-by: Mika Westerberg --- drivers/thunderbolt/nhi.c | 5 +++++ include/linux/thunderbolt.h | 3 +++ 2 files changed, 8 insertions(+) diff --git a/drivers/thunderbolt/nhi.c b/drivers/thunderbolt/nhi.c index 5809809f6..d4d1efa2a 100644 --- a/drivers/thunderbolt/nhi.c +++ b/drivers/thunderbolt/nhi.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -560,6 +561,8 @@ static struct tb_ring *tb_ring_alloc(struct tb_nhi *nhi, u32 hop, int size, INIT_LIST_HEAD(&ring->in_flight); INIT_WORK(&ring->work, ring_work); init_waitqueue_head(&ring->wait); + lockdep_register_key(&ring->lock_key); + lockdep_init_map(&ring->work.lockdep_map, "ring.work", &ring->lock_key, 0); ring->nhi = nhi; ring->hop = hop; @@ -599,6 +602,7 @@ err_free_descs: ring->size * sizeof(*ring->descriptors), ring->descriptors, ring->descriptors_dma); err_free_ring: + lockdep_unregister_key(&ring->lock_key); kfree(ring); return NULL; @@ -848,6 +852,7 @@ void tb_ring_free(struct tb_ring *ring) * to finish before freeing the ring. */ flush_work(&ring->work); + lockdep_unregister_key(&ring->lock_key); kfree(ring); } EXPORT_SYMBOL_GPL(tb_ring_free); diff --git a/include/linux/thunderbolt.h b/include/linux/thunderbolt.h index d48623fda..b62dfa52b 100644 --- a/include/linux/thunderbolt.h +++ b/include/linux/thunderbolt.h @@ -22,6 +22,7 @@ struct device; #include #include #include +#include #include #include #include @@ -565,6 +566,7 @@ struct tb_nhi { * @interval_nsec: Interval counter if interrupt throttling is to be * used with this ring (in ns) * @wait: Used to signal that the ring may be empty now + * @lock_key: Lock validator class key per-ring */ struct tb_ring { spinlock_t lock; @@ -590,6 +592,7 @@ struct tb_ring { void *poll_data; unsigned int interval_nsec; wait_queue_head_t wait; + struct lock_class_key lock_key; }; /* Leave ring interrupt enabled on suspend */ -- cgit v1.3.1