Increase LOCKDEP_CIRCULAR_QUEUE_BITS to avoid this warning: ------------[ cut here ]------------ lockdep bfs error:-1 WARNING: kernel/locking/lockdep.c:2059 at print_bfs_bug+0x20/0x40 kernel/locking/lockdep.c:2059, CPU#0: syz.2.2193/12255 Modules linked in: CPU: 0 UID: 0 PID: 12255 Comm: syz.2.2193 Tainted: G L syzkaller #0 PREEMPT_{RT,(full)} Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 RIP: 0010:print_bfs_bug+0x22/0x40 kernel/locking/lockdep.c:2059 Code: 90 90 90 90 90 90 90 90 55 53 89 fb e8 a7 aa fa 02 89 c5 e8 30 8a ff ff 85 ed 74 13 83 fb ff 74 16 48 8d 3d b0 0f cd 0d 89 de <67> 48 0f b9 3a 5b 5d c3 cc cc cc cc cc 48 c7 c7 d5 e0 6d 8d e8 f5 RSP: 0018:ffffc90003b0ef90 EFLAGS: 00010046 RAX: 000000000000003b RBX: 00000000ffffffff RCX: d0b09708318c8300 RDX: ffffc9000eb03000 RSI: 00000000ffffffff RDI: ffffffff8f6d9f50 RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000 R10: dffffc0000000000 R11: fffff52000761da1 R12: ffffffff960e0928 R13: ffffffff930a5228 R14: ffff88802ebc8000 R15: 0000000000000020 FS: 00007f05a7dce6c0(0000) GS:ffff888126332000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000002000 CR3: 00000000292da000 CR4: 00000000003526f0 Call Trace: check_irq_usage kernel/locking/lockdep.c:-1 [inline] check_prev_add kernel/locking/lockdep.c:3169 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x2550/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868 _raw_spin_lock_nested+0x32/0x50 kernel/locking/spinlock.c:378 raw_spin_rq_lock_nested+0xb6/0x150 kernel/sched/core.c:655 raw_spin_rq_lock kernel/sched/sched.h:1618 [inline] _task_rq_lock+0xbc/0x470 kernel/sched/core.c:747 class_task_rq_lock_constructor kernel/sched/sched.h:1920 [inline] migrate_disable_switch kernel/sched/core.c:2366 [inline] __schedule+0x16d3/0x5240 kernel/sched/core.c:6795 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7238 irqentry_exit+0x599/0x620 kernel/entry/common.c:239 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:688 RIP: 0010:lock_acquire+0x20b/0x2e0 kernel/locking/lockdep.c:5872 Code: e9 30 ff ff ff e8 55 1d 84 09 f7 c3 00 02 00 00 0f 84 38 ff ff ff 65 48 8b 05 c1 aa ae 10 48 3b 44 24 30 75 33 fb 48 83 c4 38 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 48 8d 3d de 63 cd RSP: 0018:ffffc90003b0f540 EFLAGS: 00000292 RAX: d0b09708318c8300 RBX: 0000000000000246 RCX: 0000000000000046 RDX: 0000000000000006 RSI: ffffffff8d7c20a5 RDI: ffffffff8ba67a80 RBP: 0000000000000000 R08: 0000000000000002 R09: ffffffff9597ac68 R10: 000000004bd204ac R11: 00000000816509e3 R12: 0000000000000000 R13: ffff8880650d0230 R14: 0000000000000000 R15: 0000000000000001 rt_spin_lock+0x83/0x400 kernel/locking/spinlock_rt.c:56 spin_lock_bh include/linux/spinlock_rt.h:90 [inline] dev_reset_queue+0x160/0x1f0 include/net/sch_generic.h:735 netdev_for_each_tx_queue include/linux/netdevice.h:2684 [inline] dev_deactivate_many+0x71f/0xd40 net/sched/sch_generic.c:1345 __dev_close_many+0x17b/0x6d0 net/core/dev.c:1759 netif_close_many+0x225/0x420 net/core/dev.c:1800 unregister_netdevice_many_notify+0xb47/0x2360 net/core/dev.c:12401 unregister_netdevice_many net/core/dev.c:12494 [inline] unregister_netdevice_queue+0x31f/0x360 net/core/dev.c:12308 unregister_netdevice include/linux/netdevice.h:3409 [inline] ppp_release+0xf0/0x1f0 drivers/net/ppp/ppp_generic.c:415 __fput+0x461/0xa90 fs/file_table.c:469 task_work_run+0x1d9/0x270 kernel/task_work.c:233 get_signal+0x11c3/0x1310 kernel/signal.c:2807 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline] exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline] do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f05a9b7c819 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f05a7dce028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: 0000000000000040 RBX: 00007f05a9df5fa0 RCX: 00007f05a9b7c819 RDX: 0000000000004000 RSI: 0000200000000280 RDI: 0000000000000003 RBP: 00007f05a9c12c91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f05a9df6038 R14: 00007f05a9df5fa0 R15: 00007ffe1e578298 ---------------- Code disassembly (best guess): 0: 90 nop 1: 90 nop 2: 90 nop 3: 90 nop 4: 90 nop 5: 90 nop 6: 90 nop 7: 90 nop 8: 55 push %rbp 9: 53 push %rbx a: 89 fb mov %edi,%ebx c: e8 a7 aa fa 02 call 0x2faaab8 11: 89 c5 mov %eax,%ebp 13: e8 30 8a ff ff call 0xffff8a48 18: 85 ed test %ebp,%ebp 1a: 74 13 je 0x2f 1c: 83 fb ff cmp $0xffffffff,%ebx 1f: 74 16 je 0x37 21: 48 8d 3d b0 0f cd 0d lea 0xdcd0fb0(%rip),%rdi # 0xdcd0fd8 28: 89 de mov %ebx,%esi * 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction 2f: 5b pop %rbx 30: 5d pop %rbp 31: c3 ret 32: cc int3 33: cc int3 34: cc int3 35: cc int3 36: cc int3 37: 48 c7 c7 d5 e0 6d 8d mov $0xffffffff8d6de0d5,%rdi 3e: e8 .byte 0xe8 3f: f5 cmc