INFO: rcu detected stall in fcntl

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-6.1	INFO: rcu detected stall in fcntl	1				1	106d	106d	0/3	auto-obsoleted due to no activity on 2026/03/30 11:32

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P6169/1:b..l
	(detected by 0, t=10502 jiffies, g=133653, q=10)
task:udevd           state:R  running task     stack:23120 pid: 6169 ppid:  3562 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
 preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6799
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_reschedule_ipi+0x16/0x20 arch/x86/include/asm/idtentry.h:681
RIP: 0010:__rcu_read_unlock+0x0/0xd0 kernel/rcu/tree_plugin.h:415
Code: c0 75 11 ff 03 8b 03 3d 00 00 00 40 7d 02 5b c3 0f 0b eb fa 89 d9 80 e1 07 80 c1 03 38 c1 7c e3 48 89 df e8 f2 af 58 00 eb d9 <41> 57 41 56 41 55 41 54 53 49 bf 00 00 00 00 00 fc ff df 65 48 8b
RSP: 0018:ffffc9000133f7b0 EFLAGS: 00000293
RAX: ffffffff83ac402a RBX: 0000000000000000 RCX: ffff888027bc1dc0
RDX: 0000000000000000 RSI: ffffffff8a79f960 RDI: ffffffff8a79f920
RBP: 0000000000000001 R08: dffffc0000000000 R09: 1ffffffff203a818
R10: dffffc0000000000 R11: fffffbfff203a819 R12: dffffc0000000000
R13: ffff888016e31118 R14: 0000000000000001 R15: 0000000000000001
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 devcgroup_legacy_check_permission security/device_cgroup.c:848 [inline]
 devcgroup_check_permission+0x7f7/0x8c0 security/device_cgroup.c:868
 blkdev_get_by_dev+0x52/0xa60 block/bdev.c:800
 blkdev_open+0x12d/0x2c0 block/fops.c:466
 do_dentry_open+0x7ff/0xf80 fs/open.c:826
 do_open fs/namei.c:3616 [inline]
 path_openat+0x26f5/0x2fa0 fs/namei.c:3750
 do_filp_open+0x1e2/0x410 fs/namei.c:3777
 do_sys_openat2+0x150/0x4b0 fs/open.c:1255
 do_sys_open fs/open.c:1271 [inline]
 __do_sys_openat fs/open.c:1287 [inline]
 __se_sys_openat fs/open.c:1282 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1282
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f4aface4407
RSP: 002b:00007ffc9cc946c0 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f4afabf6880 RCX: 00007f4aface4407
RDX: 0000000000080000 RSI: 000055a2765c7b20 RDI: ffffffffffffff9c
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000055a26e7e495f
R13: 000055a26e7f5660 R14: 0000000000000000 R15: 00000000ffffffff
 </TASK>
rcu: rcu_preempt kthread starved for 10537 jiffies! g133653 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:26928 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2117
 rcu_gp_fqs_loop+0x2be/0x11d0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x9b/0x370 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
NMI backtrace for cpu 0
CPU: 0 PID: 24659 Comm: syz.3.4980 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_check_gp_kthread_starvation+0x1cd/0x250 kernel/rcu/tree_stall.h:487
 print_other_cpu_stall+0x1110/0x1270 kernel/rcu/tree_stall.h:592
 check_cpu_stall kernel/rcu/tree_stall.h:745 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x843/0x1120 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:2021
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4b4/0xb70 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:unwind_next_frame+0x3d/0x1d90 arch/x86/kernel/unwind_orc.c:424
Code: fb 49 be 00 00 00 00 00 fc ff df 48 8d 6f 48 48 89 e8 48 c1 e8 03 48 89 44 24 20 42 80 3c 30 00 74 08 48 89 ef e8 b3 1f 89 00 <4c> 8b 63 48 4c 8d 7b 38 4c 89 f8 48 c1 e8 03 48 89 44 24 40 42 80
RSP: 0018:ffffc9000472f548 EFLAGS: 00000246
RAX: 1ffff920008e5eca RBX: ffffc9000472f608 RCX: 0000000080000001
RDX: dffffc0000000000 RSI: ffffffff81be278f RDI: ffffc9000472f608
RBP: ffffc9000472f650 R08: ffffc9000472f6d0 R09: 0000000000000001
R10: dffffc0000000000 R11: fffff520008e5ecd R12: ffff888054208000
R13: ffff888066d593f0 R14: dffffc0000000000 R15: ffffc9000472f608
 arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xea/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kmem_cache_free+0x8f/0x210 mm/slub.c:3520
 locks_free_lock fs/locks.c:411 [inline]
 posix_lock_inode+0x2510/0x3200 fs/locks.c:1402
 posix_lock_file fs/locks.c:1427 [inline]
 vfs_lock_file fs/locks.c:2400 [inline]
 do_lock_file_wait fs/locks.c:2414 [inline]
 fcntl_setlk+0x95a/0xfc0 fs/locks.c:2492
 do_fcntl+0x533/0x1360 fs/fcntl.c:373
 __do_sys_fcntl fs/fcntl.c:466 [inline]
 __se_sys_fcntl+0xcc/0x190 fs/fcntl.c:451
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f11df4ab799
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:00007f11dd705028 EFLAGS: 00000246 ORIG_RAX: 0000000000000048
RAX: ffffffffffffffda RBX: 00007f11df724fa0 RCX: 00007f11df4ab799
RDX: 0000200000000280 RSI: 0000000000000026 RDI: 0000000000000005
RBP: 00007f11df541bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f11df725038 R14: 00007f11df724fa0 R15: 00007fffdf021d08
 </TASK>
vkms_vblank_simulate: vblank timer overrun

Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info	Assets (help?)	Manager	Title
2026/03/06 10:47	linux-5.15.y	91d48252ad4b	31e9c887	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci2-linux-5-15-kasan	INFO: rcu detected stall in fcntl
2026/02/28 14:18	linux-5.15.y	3330a8d33e08	43249bac	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci2-linux-5-15-kasan	INFO: rcu detected stall in fcntl
2026/02/12 22:45	linux-5.15.y	e45d5d41c134	504cb1bf	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci2-linux-5-15-kasan	INFO: rcu detected stall in fcntl
2026/01/28 08:04	linux-5.15.y	9eec9a14ee10	3029c699	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci2-linux-5-15-kasan	INFO: rcu detected stall in fcntl