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With CONFIG_LOCKDEP=y and CONFIG_DEBUG_SPINLOCK=y, lockdep reports below warning: [ 166.059415] ============================================ [ 166.059416] WARNING: possible recursive locking detected [ 166.059418] 5.15.0-wt-ath+ #10 Tainted: G W O [ 166.059420] -------------------------------------------- [ 166.059421] kworker/0:2/116 is trying to acquire lock: [ 166.059423] ffff9905f2083160 (&srng->lock){+.-.}-{2:2}, at: ath11k_hal_reo_cmd_send+0x20/0x490 [ath11k] [ 166.059440] but task is already holding lock: [ 166.059442] ffff9905f2083230 (&srng->lock){+.-.}-{2:2}, at: ath11k_dp_process_reo_status+0x95/0x2d0 [ath11k] [ 166.059491] other info that might help us debug this: [ 166.059492] Possible unsafe locking scenario: [ 166.059493] CPU0 [ 166.059494] ---- [ 166.059495] lock(&srng->lock); [ 166.059498] lock(&srng->lock); [ 166.059500] *** DEADLOCK *** [ 166.059501] May be due to missing lock nesting notation [ 166.059502] 3 locks held by kworker/0:2/116: [ 166.059504] #0: ffff9905c0081548 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1f6/0x660 [ 166.059511] #1: ffff9d2400a5fe68 ((debug_obj_work).work){+.+.}-{0:0}, at: process_one_work+0x1f6/0x660 [ 166.059517] #2: ffff9905f2083230 (&srng->lock){+.-.}-{2:2}, at: ath11k_dp_process_reo_status+0x95/0x2d0 [ath11k] [ 166.059532] stack backtrace: [ 166.059534] CPU: 0 PID: 116 Comm: kworker/0:2 Kdump: loaded Tainted: G W O 5.15.0-wt-ath+ #10 [ 166.059537] Hardware name: Intel(R) Client Systems NUC8i7HVK/NUC8i7HVB, BIOS HNKBLi70.86A.0059.2019.1112.1124 11/12/2019 [ 166.059539] Workqueue: events free_obj_work [ 166.059543] Call Trace: [ 166.059545] <IRQ> [ 166.059547] dump_stack_lvl+0x56/0x7b [ 166.059552] __lock_acquire+0xb9a/0x1a50 [ 166.059556] lock_acquire+0x1e2/0x330 [ 166.059560] ? ath11k_hal_reo_cmd_send+0x20/0x490 [ath11k] [ 166.059571] _raw_spin_lock_bh+0x33/0x70 [ 166.059574] ? ath11k_hal_reo_cmd_send+0x20/0x490 [ath11k] [ 166.059584] ath11k_hal_reo_cmd_send+0x20/0x490 [ath11k] [ 166.059594] ath11k_dp_tx_send_reo_cmd+0x3f/0x130 [ath11k] [ 166.059605] ath11k_dp_rx_tid_del_func+0x221/0x370 [ath11k] [ 166.059618] ath11k_dp_process_reo_status+0x22f/0x2d0 [ath11k] [ 166.059632] ? ath11k_dp_service_srng+0x2ea/0x2f0 [ath11k] [ 166.059643] ath11k_dp_service_srng+0x2ea/0x2f0 [ath11k] [ 166.059655] ath11k_pci_ext_grp_napi_poll+0x1c/0x70 [ath11k_pci] [ 166.059659] __napi_poll+0x28/0x230 [ 166.059664] net_rx_action+0x285/0x310 [ 166.059668] __do_softirq+0xe6/0x4d2 [ 166.059672] irq_exit_rcu+0xd2/0xf0 [ 166.059675] common_interrupt+0xa5/0xc0 [ 166.059678] </IRQ> [ 166.059679] <TASK> [ 166.059680] asm_common_interrupt+0x1e/0x40 [ 166.059683] RIP: 0010:_raw_spin_unlock_irqrestore+0x38/0x70 [ 166.059686] Code: 83 c7 18 e8 2a 95 43 ff 48 89 ef e8 22 d2 43 ff 81 e3 00 02 00 00 75 25 9c 58 f6 c4 02 75 2d 48 85 db 74 01 fb bf 01 00 00 00 <e8> 63 2e 40 ff 65 8b 05 8c 59 97 5c 85 c0 74 0a 5b 5d c3 e8 00 6a [ 166.059689] RSP: 0018:ffff9d2400a5fca0 EFLAGS: 00000206 [ 166.059692] RAX: 0000000000000002 RBX: 0000000000000200 RCX: 0000000000000006 [ 166.059694] RDX: 0000000000000000 RSI: ffffffffa404879b RDI: 0000000000000001 [ 166.059696] RBP: ffff9905c0053000 R08: 0000000000000001 R09: 0000000000000001 [ 166.059698] R10: ffff9d2400a5fc50 R11: 0000000000000001 R12: ffffe186c41e2840 [ 166.059700] R13: 0000000000000001 R14: ffff9905c78a1c68 R15: 0000000000000001 [ 166.059704] free_debug_processing+0x257/0x3d0 [ 166.059708] ? free_obj_work+0x1f5/0x250 [ 166.059712] __slab_free+0x374/0x5a0 [ 166.059718] ? kmem_cache_free+0x2e1/0x370 [ 166.059721] ? free_obj_work+0x1f5/0x250 [ 166.059724] kmem_cache_free+0x2e1/0x370 [ 166.059727] free_obj_work+0x1f5/0x250 [ 166.059731] process_one_work+0x28b/0x660 [ 166.059735] ? process_one_work+0x660/0x660 [ 166.059738] worker_thread+0x37/0x390 [ 166.059741] ? process_one_work+0x660/0x660 [ 166.059743] kthread+0x176/0x1a0 [ 166.059746] ? set_kthread_struct+0x40/0x40 [ 166.059749] ret_from_fork+0x22/0x30 [ 166.059754] </TASK> Since these two lockes are both initialized in ath11k_hal_srng_setup, they are assigned with the same key. As a result lockdep suspects that the task is trying to acquire the same lock (due to same key) while already holding it, and thus reports the DEADLOCK warning. However as they are different spinlock instances, the warning is false positive. On the other hand, even no dead lock indeed, this is a major issue for upstream regression testing as it disables lockdep functionality. Fix it by assigning separate lock class key for each srng->lock. Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-01720.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1 Signed-off-by: Baochen Qiang <quic_bqiang@quicinc.com> Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com> Link: https://lore.kernel.org/r/20211209011949.151472-1-quic_bqiang@quicinc.com |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.