On Linux mainline kernel 5.6.0 running kselftest on i386 kernel running on x86_64 devices we have noticed this kernel warning.
[ 0.000000] Linux version 5.6.0 (oe-user@oe-host) (gcc version 7.3.0 (GCC)) #1 SMP Mon Apr 6 17:31:22 UTC 2020 <> [ 143.321511] ------------[ cut here ]------------ [ 143.326180] WARNING: CPU: 1 PID: 1515 at /usr/src/kernel/kernel/locking/lockdep.c:1155 lockdep_register_key+0x150/0x180 [ 143.336958] Modules linked in: sch_ingress veth algif_hash x86_pkg_temp_thermal fuse [ 143.344698] CPU: 1 PID: 1515 Comm: ip Tainted: G W 5.6.0 #1 [ 143.351562] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS 2.0b 07/27/2017 [ 143.359034] EIP: lockdep_register_key+0x150/0x180 [ 143.363739] Code: ff ff a1 88 4c 2a dc 85 c0 0f 85 ef fe ff ff 68 27 02 f9 db 68 a5 7a f7 db e8 0c 5b fa ff 0f 0b 59 58 e9 d7 fe ff ff 8d 76 00 <0f> 0b 8d 65 f8 5b 5e 5d c3 8d b4 26 00 00 00 00 89 c2 b8 68 68 99 [ 143.382485] EAX: 00000001 EBX: dc329ea8 ECX: 00000001 EDX: dc3299a8 [ 143.388751] ESI: 00000001 EDI: c7316000 EBP: c610fe10 ESP: c610fe08 [ 143.395014] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010202 [ 143.401792] CR0: 80050033 CR2: b7dd70c0 CR3: 20672000 CR4: 003406d0 [ 143.408051] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000 [ 143.414315] DR6: fffe0ff0 DR7: 00000400 [ 143.418144] Call Trace: [ 143.420592] alloc_netdev_mqs+0xc6/0x3c0 [ 143.424520] __ip_tunnel_create+0xa1/0x1d0 [ 143.428614] ? ipgre_tap_setup+0x50/0x50 [ 143.432535] ? mutex_lock_nested+0x19/0x20 [ 143.436634] ip_tunnel_init_net+0x125/0x340 [ 143.440823] erspan_init_net+0x1d/0x20 [ 143.444580] ops_init+0x34/0x180 [ 143.447815] setup_net+0xe7/0x230 [ 143.451134] copy_net_ns+0xe0/0x210 [ 143.454625] create_new_namespaces+0xf5/0x290 [ 143.458984] unshare_nsproxy_namespaces+0x47/0xa0 [ 143.463691] ksys_unshare+0x19e/0x330 [ 143.467354] ? __might_fault+0x41/0x80 [ 143.471102] __ia32_sys_unshare+0xf/0x20 [ 143.475026] do_fast_syscall_32+0x7f/0x330 [ 143.479126] entry_SYSENTER_32+0xaa/0x102 [ 143.483135] EIP: 0xb7f77ce1 [ 143.485926] Code: 5e 5d c3 8d b6 00 00 00 00 b8 40 42 0f 00 eb c1 8b 04 24 c3 8b 1c 24 c3 8b 34 24 c3 8b 3c 24 c3 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d 76 00 58 b8 77 00 00 00 cd 80 90 8d 76 [ 143.504662] EAX: ffffffda EBX: 40000000 ECX: 080a8b31 EDX: 00000000 [ 143.510920] ESI: 00000001 EDI: bf833230 EBP: bf830fc0 ESP: bf830f7c [ 143.517177] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b EFLAGS: 00000292 [ 143.523959] irq event stamp: 5894 [ 143.527275] hardirqs last enabled at (5893): [<dbc0225a>] _raw_spin_unlock_irqrestore+0x2a/0x50 [ 143.536054] hardirqs last disabled at (5894): [<dae019dc>] trace_hardirqs_off_thunk+0xc/0x10 [ 143.544487] softirqs last enabled at (5882): [<dba45069>] inet6_fill_ifla6_attrs+0x3b9/0x400 [ 143.553004] softirqs last disabled at (5880): [<dba4504b>] inet6_fill_ifla6_attrs+0x39b/0x400 [ 143.561514] ---[ end trace dbec531a9fb3b99c ]---
Full test log, https://lkft.validation.linaro.org/scheduler/job/1341969#L5766