INFO: rcu detected stall in legacy_kthread

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (1 GPs behind) idle=2634/1/0x4000000000000000 softirq=0/0 fqs=14 rcuc=14862 jiffies(starved)
rcu: 	         hardirqs   softirqs   csw/system
rcu: 	 number:     5197       5504         5041
rcu: 	cputime:    17057        676        21915   ==> 39660(ms)
rcu: 	(t=10500 jiffies g=71857 q=761 ncpus=2)
rcu: rcu_preempt kthread starved for 2591 jiffies! g71857 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:26264 pid:18    tgid:18    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x16f3/0x4c20 kernel/sched/core.c:6929
 __schedule_loop kernel/sched/core.c:7011 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7026
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 3434 Comm: kworker/R-bat_e Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: bat_events batadv_tt_purge
RIP: 0010:check_kcov_mode kernel/kcov.c:183 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:246 [inline]
RIP: 0010:__sanitizer_cov_trace_switch+0xb9/0x150 kernel/kcov.c:351
Code: 39 c8 0f 84 86 00 00 00 4e 8b 5c ce 10 65 8b 2d 7d 7b e3 0f 81 e5 00 00 ff 00 41 8b 98 4c 0b 00 00 44 21 d3 41 89 de 41 09 ee <74> 12 85 ed 75 cc 85 db 74 c8 41 83 b8 14 16 00 00 00 74 be 41 8b
RSP: 0018:ffffc9000d1e6a50 EFLAGS: 00000046
RAX: 0000000000000020 RBX: 0000000000000000 RCX: 0000000000000005
RDX: ffffffff81c09c95 RSI: ffffffff8d6017a0 RDI: 0000000000000004
RBP: 0000000000000000 R08: ffff8880308d9e00 R09: 0000000000000005
R10: 0000000000000100 R11: 0000000000000005 R12: dffffc0000000000
R13: ffff88813ff7b010 R14: 0000000000000000 R15: 0000000000049344
FS:  0000000000000000(0000) GS:ffff888126dfc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f56be093aa1 CR3: 000000005b8d4000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 rb_event_length+0x45/0x400 kernel/trace/ring_buffer.c:222
 rb_read_data_buffer+0x438/0x580 kernel/trace/ring_buffer.c:1823
 check_buffer+0x28a/0x750 kernel/trace/ring_buffer.c:4394
 __rb_reserve_next+0x592/0xdb0 kernel/trace/ring_buffer.c:4493
 rb_reserve_next_event kernel/trace/ring_buffer.c:4630 [inline]
 ring_buffer_lock_reserve+0xbb5/0x1010 kernel/trace/ring_buffer.c:4689
 __trace_buffer_lock_reserve kernel/trace/trace.c:1081 [inline]
 trace_event_buffer_lock_reserve+0x1d0/0x6f0 kernel/trace/trace.c:2799
 trace_event_buffer_reserve+0x248/0x340 kernel/trace/trace_events.c:672
 do_trace_event_raw_event_bpf_trace_printk kernel/trace/bpf_trace.h:11 [inline]
 trace_event_raw_event_bpf_trace_printk+0x100/0x260 kernel/trace/bpf_trace.h:11
 __do_trace_bpf_trace_printk kernel/trace/bpf_trace.h:11 [inline]
 trace_bpf_trace_printk+0x170/0x1d0 kernel/trace/bpf_trace.h:11
 ____bpf_trace_printk kernel/trace/bpf_trace.c:379 [inline]
 bpf_trace_printk+0x11e/0x190 kernel/trace/bpf_trace.c:362
 bpf_prog_b1367f0be6c54012+0x39/0x3f
 bpf_dispatcher_nop_func include/linux/bpf.h:1350 [inline]
 __bpf_prog_run include/linux/filter.h:721 [inline]
 bpf_prog_run include/linux/filter.h:728 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2075 [inline]
 bpf_trace_run1+0x27f/0x4b0 kernel/trace/bpf_trace.c:2115
 __bpf_trace_rcu_utilization+0xa1/0xf0 include/trace/events/rcu.h:27
 __traceiter_rcu_utilization+0x7a/0xb0 include/trace/events/rcu.h:27
 __do_trace_rcu_utilization include/trace/events/rcu.h:27 [inline]
 trace_rcu_utilization+0x1ad/0x1d0 include/trace/events/rcu.h:27
 rcu_note_context_switch+0xc9/0x1140 kernel/rcu/tree_plugin.h:330
 __schedule+0x30e/0x4c20 kernel/sched/core.c:6814
 preempt_schedule_notrace+0xd1/0x110 kernel/sched/core.c:7206
 preempt_schedule_notrace_thunk+0x16/0x30 arch/x86/entry/thunk.S:13
 rcu_is_watching+0x7f/0xb0 kernel/rcu/tree.c:752
 trace_lock_acquire include/trace/events/lock.h:24 [inline]
 lock_acquire+0x5f/0x360 kernel/locking/lockdep.c:5831
 __local_bh_disable_ip+0xc5/0x540 kernel/softirq.c:163
 local_bh_disable include/linux/bottom_half.h:20 [inline]
 spin_lock_bh include/linux/spinlock_rt.h:87 [inline]
 batadv_tt_local_purge+0x136/0x380 net/batman-adv/translation-table.c:1313
 batadv_tt_purge+0x35/0xa10 net/batman-adv/translation-table.c:3509
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
 rescuer_thread+0x53c/0xdd0 kernel/workqueue.c:3523
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
CPU: 1 UID: 0 PID: 5802 Comm: kworker/u9:3 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue:  0x0 (krxrpcd)
RIP: 0010:finish_task_switch+0x26b/0x950 kernel/sched/core.c:5193
Code: 0f 84 bd 01 00 00 48 85 db 0f 85 e4 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 9f fb 32 09 e8 0a ba 35 00 fb 4c 8b 65 c0 <49> 8d bc 24 f0 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0018:ffffc90004d6f998 EFLAGS: 00000282
RAX: 057fb6640b1ce700 RBX: 0000000000000000 RCX: 057fb6640b1ce700
RDX: 0000000000000000 RSI: ffffffff8cd8c5cf RDI: ffffffff8b3ddbe0
RBP: ffffc90004d6f9f0 R08: ffffffff8ed62977 R09: 1ffffffff1dac52e
R10: dffffc0000000000 R11: fffffbfff1dac52f R12: ffff8880388dda00
R13: dffffc0000000000 R14: ffff88801bea1e00 R15: ffff8880b893b958
FS:  0000000000000000(0000) GS:ffff888126efc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007feeb75456c0 CR3: 00000000586c2000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0x16fb/0x4c20 kernel/sched/core.c:6929
 __schedule_loop kernel/sched/core.c:7011 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7026
 worker_thread+0xa82/0xda0 kernel/workqueue.c:3442
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 17 Comm: pr/legacy Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:preempt_count arch/x86/include/asm/preempt.h:27 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:183 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:246 [inline]
RIP: 0010:__sanitizer_cov_trace_switch+0x9c/0x150 kernel/kcov.c:351
Code: 48 8b 54 24 30 65 4c 8b 04 25 08 40 a2 91 45 31 c9 41 ba 00 01 00 00 eb 0c 49 ff c1 4c 39 c8 0f 84 86 00 00 00 4e 8b 5c ce 10 <65> 8b 2d 7d 7b e3 0f 81 e5 00 00 ff 00 41 8b 98 4c 0b 00 00 44 21
RSP: 0018:ffffc90000a78398 EFLAGS: 00000002
RAX: 0000000000000020 RBX: 0000000000000000 RCX: 0000000000000005
RDX: ffffffff81c2a4d0 RSI: ffffffff8d601e90 RDI: 0000000000000004
RBP: 0000000000010000 R08: ffff88801b6f0000 R09: 0000000000000010
R10: 0000000000000100 R11: 0000000000000010 R12: ffff88801beea010
R13: 0000000000000004 R14: 0000000000010000 R15: 0000000000000b7c
FS:  0000000000000000(0000) GS:ffff888126efc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007feeb75456c0 CR3: 0000000061c64000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 rb_read_data_buffer+0x110/0x580 kernel/trace/ring_buffer.c:1827
 check_buffer+0x28a/0x750 kernel/trace/ring_buffer.c:4394
 __rb_reserve_next+0x592/0xdb0 kernel/trace/ring_buffer.c:4493
 rb_reserve_next_event kernel/trace/ring_buffer.c:4630 [inline]
 ring_buffer_lock_reserve+0xbb5/0x1010 kernel/trace/ring_buffer.c:4689
 __trace_buffer_lock_reserve kernel/trace/trace.c:1081 [inline]
 trace_event_buffer_lock_reserve+0x1d0/0x6f0 kernel/trace/trace.c:2799
 trace_event_buffer_reserve+0x248/0x340 kernel/trace/trace_events.c:672
 do_trace_event_raw_event_bpf_trace_printk kernel/trace/bpf_trace.h:11 [inline]
 trace_event_raw_event_bpf_trace_printk+0x100/0x260 kernel/trace/bpf_trace.h:11
 __do_trace_bpf_trace_printk kernel/trace/bpf_trace.h:11 [inline]
 trace_bpf_trace_printk+0x170/0x1d0 kernel/trace/bpf_trace.h:11
 ____bpf_trace_printk kernel/trace/bpf_trace.c:379 [inline]
 bpf_trace_printk+0x11e/0x190 kernel/trace/bpf_trace.c:362
 bpf_prog_b1367f0be6c54012+0x39/0x3f
 bpf_dispatcher_nop_func include/linux/bpf.h:1350 [inline]
 __bpf_prog_run include/linux/filter.h:721 [inline]
 bpf_prog_run include/linux/filter.h:728 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2075 [inline]
 bpf_trace_run1+0x27f/0x4b0 kernel/trace/bpf_trace.c:2115
 __bpf_trace_rcu_utilization+0xa1/0xf0 include/trace/events/rcu.h:27
 __traceiter_rcu_utilization+0x7a/0xb0 include/trace/events/rcu.h:27
 __do_trace_rcu_utilization include/trace/events/rcu.h:27 [inline]
 trace_rcu_utilization+0x1ad/0x1d0 include/trace/events/rcu.h:27
 rcu_sched_clock_irq+0xd3/0x11b0 kernel/rcu/tree.c:2693
 update_process_times+0x235/0x2d0 kernel/time/timer.c:2473
 tick_sched_handle kernel/time/tick-sched.c:276 [inline]
 tick_nohz_handler+0x39a/0x520 kernel/time/tick-sched.c:297
 __run_hrtimer kernel/time/hrtimer.c:1777 [inline]
 __hrtimer_run_queues+0x506/0xd40 kernel/time/hrtimer.c:1841
 hrtimer_interrupt+0x45d/0xa90 kernel/time/hrtimer.c:1903
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1041 [inline]
 __sysvec_apic_timer_interrupt+0x10b/0x410 arch/x86/kernel/apic/apic.c:1058
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline]
 sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1052
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:finish_task_switch+0x26b/0x950 kernel/sched/core.c:5193
Code: 0f 84 bd 01 00 00 48 85 db 0f 85 e4 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 9f fb 32 09 e8 0a ba 35 00 fb 4c 8b 65 c0 <49> 8d bc 24 f0 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0018:ffffc900001674d8 EFLAGS: 00000286
RAX: de84ca0431209a00 RBX: 0000000000000000 RCX: de84ca0431209a00
RDX: 0000000000000006 RSI: ffffffff8cd8c5cf RDI: ffffffff8b3ddbe0
RBP: ffffc90000167530 R08: ffffffff8ed62977 R09: 1ffffffff1dac52e
R10: dffffc0000000000 R11: fffffbfff1dac52f R12: ffff88801b6f0000
R13: dffffc0000000000 R14: ffff88801bea1e00 R15: ffff8880b893b958
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0x16fb/0x4c20 kernel/sched/core.c:6929
 preempt_schedule_common+0x83/0xd0 kernel/sched/core.c:7113
 preempt_schedule+0xae/0xc0 kernel/sched/core.c:7137
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 delay_tsc+0x7a/0xc0 arch/x86/lib/delay.c:77
 udelay include/asm-generic/delay.h:62 [inline]
 wait_for_lsr+0x166/0x2f0 drivers/tty/serial/8250/8250_port.c:1967
 fifo_wait_for_lsr drivers/tty/serial/8250/8250_port.c:3234 [inline]
 serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3257 [inline]
 serial8250_console_write+0x11bd/0x1b40 drivers/tty/serial/8250/8250_port.c:3342
 console_emit_next_record kernel/printk/printk.c:3091 [inline]
 console_flush_all+0x666/0xb40 kernel/printk/printk.c:3199
 __console_flush_and_unlock+0x9b/0x160 kernel/printk/printk.c:3258
 legacy_kthread_func+0x13b/0x1a0 kernel/printk/printk.c:3611
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>