Apparently, timer ain't ever supposed to be running when you get there
via flush_delayed_work(), but it was.
[ 28.932213] BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:969
[ 28.932220] in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 336, name: systemd-udevd
[ 28.932223] 1 lock held by systemd-udevd/336:
[ 28.932225] #0: ffff90cf9ecdb418 (&base->expiry_lock){+...}-{0:0}, at: del_timer_sync+0xfa/0x150
[ 28.932243] irq event stamp: 810843
[ 28.932245] hardirqs last enabled at (810841): [<ffffffffaf9d7170>] _raw_spin_unlock_irqrestore+0x70/0x80
[ 28.932252] hardirqs last disabled at (810842): [<ffffffffaf0b2b09>] flush_delayed_work+0x49/0x50
[ 28.932259] softirqs last enabled at (807242): [<ffffffffaf095825>] __local_bh_enable_ip+0x75/0x130
[ 28.932266] softirqs last disabled at (810843): [<ffffffffaf14eca3>] del_timer_sync+0xd3/0x150
[ 28.932271] CPU: 6 PID: 336 Comm: systemd-udevd Tainted: G E 5.10.0.g07e0887-rt2-rt #18
[ 28.932275] Hardware name: MEDION MS-7848/MS-7848, BIOS M7848W08.20C 09/23/2013
[ 28.932277] Call Trace:
[ 28.932288] dump_stack+0x77/0x97
[ 28.932304] ___might_sleep+0x14e/0x1f0
[ 28.932324] rt_spin_lock+0x3e/0xc0
[ 28.932328] ? del_timer_sync+0xfa/0x150
[ 28.932337] del_timer_sync+0xfa/0x150
[ 28.932358] flush_delayed_work+0x1a/0x50
[ 28.932366] fsnotify_destroy_group+0x58/0xd0
[ 28.932392] inotify_release+0x1e/0x50
[ 28.932402] __fput+0xb2/0x260
[ 28.932422] task_work_run+0x73/0xc0
[ 28.932444] exit_to_user_mode_prepare+0x1da/0x200
[ 28.932461] syscall_exit_to_user_mode+0x46/0x310
[ 28.932471] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 28.932477] RIP: 0033:0x7f6509e31ef4
[ 28.932483] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00 00 8b 05 7a c2 20 00 48 63 ff 85 c0 75 13 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 44 f3 c3 66 90 48 83 ec 18 48 89 7c 24 08 e8
[ 28.932487] RSP: 002b:00007ffe2518d9c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
[ 28.932491] RAX: 0000000000000000 RBX: 0000000000000008 RCX: 00007f6509e31ef4
[ 28.932493] RDX: 00007f6509e19af8 RSI: 00007f6509beaf30 RDI: 0000000000000008
[ 28.932495] RBP: 00007f650ad1cb70 R08: 000055c5ace35830 R09: 00007ffe2518eef2
[ 28.932497] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[ 28.932499] R13: 0000000000000006 R14: 00007ffe2518db04 R15: 0000000000000006
[ 28.933184] ------------[ cut here ]------------
[ 28.933185] WARNING: CPU: 6 PID: 336 at kernel/softirq.c:227 __local_bh_enable_ip+0x95/0x130
[ 28.933192] Modules linked in: hid_logitech_hidpp(E) sr_mod(E) cdrom(E) hid_logitech_dj(E) ums_realtek(E) hid_generic(E) uas(E) usb_storage(E) usbhid(E) nouveau(E) wmi(E) i2c_algo_bit(E) drm_kms_helper(E) syscopyarea(E) sysfillrect(E) sysimgblt(E) fb_sys_fops(E) xhci_pci(E) cec(E) ahci(E) ehci_pci(E) rc_core(E) libahci(E) ehci_hcd(E) xhci_hcd(E) ttm(E) libata(E) drm(E) usbcore(E) video(E) button(E) sd_mod(E) vfat(E) fat(E) virtio_blk(E) virtio_mmio(E) virtio_ring(E) virtio(E) ext4(E) crc32c_intel(E) crc16(E) mbcache(E) jbd2(E) loop(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
[ 28.933256] CPU: 6 PID: 336 Comm: systemd-udevd Tainted: G W E 5.10.0.g07e0887-rt2-rt #18
[ 28.933259] Hardware name: MEDION MS-7848/MS-7848, BIOS M7848W08.20C 09/23/2013
[ 28.933261] RIP: 0010:__local_bh_enable_ip+0x95/0x130
[ 28.933266] Code: 89 de 44 89 e7 e8 3b f9 ff ff 4d 85 ed 74 05 e8 01 04 14 00 55 9d 5b 5d 41 5c 41 5d 41 5e c3 65 8b 05 5b 48 f8 50 85 c0 75 bb <0f> 0b eb b7 e8 f2 04 14 00 eb bf 48 c7 c7 54 77 1a b0 e8 b4 43 93
[ 28.933269] RSP: 0018:ffffbbccc0417df0 EFLAGS: 00010046
[ 28.933272] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000001
[ 28.933274] RDX: 0000000000000000 RSI: 0000000000000200 RDI: ffffffffaf14eca3
[ 28.933276] RBP: ffffbbccc0417e48 R08: 0000000000000001 R09: 0000000000000000
[ 28.933278] R10: 0000000000000000 R11: ffffffffffffffff R12: 0000000000000200
[ 28.933280] R13: 000000000001c6c0 R14: ffff90cf9ecdb388 R15: ffff90cf9ecdb340
[ 28.933282] FS: 00007f650ad1cd40(0000) GS:ffff90cf9ed80000(0000) knlGS:0000000000000000
[ 28.933285] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 28.933287] CR2: 00005575baf61550 CR3: 000000010a262005 CR4: 00000000001706e0
[ 28.933289] Call Trace:
[ 28.933305] del_timer_sync+0x11b/0x150
[ 28.933325] flush_delayed_work+0x1a/0x50
[ 28.933332] fsnotify_destroy_group+0x58/0xd0
[ 28.933355] inotify_release+0x1e/0x50
[ 28.933362] __fput+0xb2/0x260
[ 28.933379] task_work_run+0x73/0xc0
[ 28.933399] exit_to_user_mode_prepare+0x1da/0x200
[ 28.933413] syscall_exit_to_user_mode+0x46/0x310
[ 28.933422] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 28.933426] RIP: 0033:0x7f6509e31ef4
[ 28.933429] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00 00 8b 05 7a c2 20 00 48 63 ff 85 c0 75 13 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 44 f3 c3 66 90 48 83 ec 18 48 89 7c 24 08 e8
[ 28.933433] RSP: 002b:00007ffe2518d9c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
[ 28.933436] RAX: 0000000000000000 RBX: 0000000000000008 RCX: 00007f6509e31ef4
[ 28.933438] RDX: 00007f6509e19af8 RSI: 00007f6509beaf30 RDI: 0000000000000008
[ 28.933439] RBP: 00007f650ad1cb70 R08: 000055c5ace35830 R09: 00007ffe2518eef2
[ 28.933441] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[ 28.933443] R13: 0000000000000006 R14: 00007ffe2518db04 R15: 0000000000000006
[ 28.933497] CPU: 6 PID: 336 Comm: systemd-udevd Tainted: G W E 5.10.0.g07e0887-rt2-rt #18
[ 28.933499] Hardware name: MEDION MS-7848/MS-7848, BIOS M7848W08.20C 09/23/2013
[ 28.933500] Call Trace:
[ 28.933505] dump_stack+0x77/0x97
[ 28.933517] __warn+0x8c/0x110
[ 28.933526] ? __local_bh_enable_ip+0x95/0x130
[ 28.933541] report_bug+0xbb/0x130
[ 28.933561] handle_bug+0x44/0x80
[ 28.933570] exc_invalid_op+0x13/0x60
[ 28.933580] asm_exc_invalid_op+0x12/0x20
[ 28.933585] RIP: 0010:__local_bh_enable_ip+0x95/0x130
[ 28.933589] Code: 89 de 44 89 e7 e8 3b f9 ff ff 4d 85 ed 74 05 e8 01 04 14 00 55 9d 5b 5d 41 5c 41 5d 41 5e c3 65 8b 05 5b 48 f8 50 85 c0 75 bb <0f> 0b eb b7 e8 f2 04 14 00 eb bf 48 c7 c7 54 77 1a b0 e8 b4 43 93
[ 28.933592] RSP: 0018:ffffbbccc0417df0 EFLAGS: 00010046
[ 28.933595] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000001
[ 28.933596] RDX: 0000000000000000 RSI: 0000000000000200 RDI: ffffffffaf14eca3
[ 28.933598] RBP: ffffbbccc0417e48 R08: 0000000000000001 R09: 0000000000000000
[ 28.933600] R10: 0000000000000000 R11: ffffffffffffffff R12: 0000000000000200
[ 28.933601] R13: 000000000001c6c0 R14: ffff90cf9ecdb388 R15: ffff90cf9ecdb340
[ 28.933638] ? del_timer_sync+0xd3/0x150
[ 28.933668] del_timer_sync+0x11b/0x150
[ 28.933686] flush_delayed_work+0x1a/0x50
[ 28.933694] fsnotify_destroy_group+0x58/0xd0
[ 28.933716] inotify_release+0x1e/0x50
[ 28.933724] __fput+0xb2/0x260
[ 28.933741] task_work_run+0x73/0xc0
[ 28.933761] exit_to_user_mode_prepare+0x1da/0x200
[ 28.933773] syscall_exit_to_user_mode+0x46/0x310
[ 28.933782] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 28.933787] RIP: 0033:0x7f6509e31ef4
[ 28.933790] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00 00 8b 05 7a c2 20 00 48 63 ff 85 c0 75 13 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 44 f3 c3 66 90 48 83 ec 18 48 89 7c 24 08 e8
[ 28.933793] RSP: 002b:00007ffe2518d9c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
[ 28.933795] RAX: 0000000000000000 RBX: 0000000000000008 RCX: 00007f6509e31ef4
[ 28.933797] RDX: 00007f6509e19af8 RSI: 00007f6509beaf30 RDI: 0000000000000008
[ 28.933799] RBP: 00007f650ad1cb70 R08: 000055c5ace35830 R09: 00007ffe2518eef2
[ 28.933800] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[ 28.933802] R13: 0000000000000006 R14: 00007ffe2518db04 R15: 0000000000000006
[ 28.933856] irq event stamp: 810843
[ 28.933857] hardirqs last enabled at (810841): [<ffffffffaf9d7170>] _raw_spin_unlock_irqrestore+0x70/0x80
[ 28.933861] hardirqs last disabled at (810842): [<ffffffffaf0b2b09>] flush_delayed_work+0x49/0x50
[ 28.933866] softirqs last enabled at (807242): [<ffffffffaf095825>] __local_bh_enable_ip+0x75/0x130
[ 28.933870] softirqs last disabled at (810843): [<ffffffffaf14eca3>] del_timer_sync+0xd3/0x150
[ 28.933874] ---[ end trace 0000000000000002 ]---
