INFO: rcu detected stall in tcp_write_timer (4)

Status: upstream: reported syz repro on 2026/03/01 05:59
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+25a2b705afb7fec8331c@syzkaller.appspotmail.com
First crash: 163d, last: 82d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/03/01 linux-5.15.y (ToT) 3330a8d33e08 syz [report] INFO: rcu detected stall in corrupted
2026/03/01 upstream (ToT) eb71ab2bf722 syz Didn't crash
▶ ▼ Similar bugs (28)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in tcp_write_timer (2) bpf 1 2 2016d 2071d 0/29 auto-closed as invalid on 2021/05/03 11:59
upstream INFO: rcu detected stall in tcp_write_timer (4) net 1 1 757d 757d 0/29 auto-obsoleted due to no activity on 2024/10/13 08:46
linux-5.15 INFO: rcu detected stall in tcp_write_timer 1 4 666d 718d 0/3 auto-obsoleted due to no activity on 2025/01/22 08:13
upstream INFO: rcu detected stall in tcp_write_timer net 1 3 2565d 2560d 0/29 auto-closed as invalid on 2019/10/25 14:11
linux-5.15 INFO: rcu detected stall in tcp_write_timer (2) 1 2 451d 535d 0/3 auto-obsoleted due to no activity on 2025/08/25 02:13
upstream INFO: rcu detected stall in tcp_write_timer (3) net 1 1 1883d 1883d 0/29 auto-closed as invalid on 2021/09/13 13:17
linux-6.1 INFO: rcu detected stall in tcp_write_timer 1 16 552d 781d 0/3 auto-obsoleted due to no activity on 2025/05/16 12:07
upstream BUG: soft lockup in tcp_write_timer (4) mm 1 4 766d 791d 26/29 fixed on 2024/07/09 19:14
linux-6.1 INFO: rcu detected stall in tcp_write_timer (2) 1 3 39d 158d 0/3 upstream: reported on 2026/03/06 03:16
linux-5.15 INFO: rcu detected stall in tcp_write_timer (3) 1 2 300d 316d 0/3 auto-obsoleted due to no activity on 2026/01/22 20:12
linux-6.6 INFO: rcu detected stall in tcp_write_timer 1 5 24d 154d 0/2 upstream: reported on 2026/03/10 11:19
linux-4.14 INFO: rcu detected stall in tcp_write_timer 1 4 2167d 2410d 0/1 auto-closed as invalid on 2021/01/02 05:45
linux-4.19 INFO: rcu detected stall in tcp_write_timer 1 2 2296d 2350d 0/1 auto-closed as invalid on 2020/08/26 06:46
upstream BUG: soft lockup in tcp_write_timer (10) perf mm net 1 3 152d 182d 0/29 closed as invalid on 2026/03/27 01:43
linux-4.19 BUG: soft lockup in tcp_write_timer (3) 1 2 1319d 1332d 0/1 upstream: reported on 2022/12/17 21:41
linux-4.19 BUG: soft lockup in tcp_write_timer (2) 1 2 1729d 1792d 0/1 auto-closed as invalid on 2022/03/16 10:56
android-54 BUG: soft lockup in tcp_write_timer 1 1 464d 464d 0/2 auto-obsoleted due to no activity on 2025/08/01 21:51
linux-4.19 BUG: soft lockup in tcp_write_timer 1 1 1958d 1958d 0/1 auto-closed as invalid on 2021/07/30 14:52
upstream BUG: soft lockup in tcp_write_timer (9) net 1 2 246d 250d 0/29 closed as invalid on 2026/01/07 12:42
upstream BUG: soft lockup in tcp_write_timer (2) kvm 1 1 1568d 1568d 0/29 auto-closed as invalid on 2022/06/24 22:31
upstream BUG: soft lockup in tcp_write_timer (3) net 1 6 945d 1053d 0/29 closed as invalid on 2024/03/18 17:07
upstream BUG: soft lockup in tcp_write_timer (7) net 1 1 331d 331d 0/29 closed as invalid on 2025/09/29 07:16
upstream BUG: soft lockup in tcp_write_timer (8) mm 1 1 307d 307d 0/29 closed as invalid on 2025/11/04 11:28
upstream BUG: soft lockup in tcp_write_timer (6) bpf 1 1 379d 379d 0/29 closed as invalid on 2025/09/01 08:24
upstream BUG: soft lockup in tcp_write_timer (5) mm net 1 8 435d 496d 0/29 closed as invalid on 2025/07/11 15:27
android-5-15 BUG: soft lockup in tcp_write_timer 1 11 729d 842d 0/2 auto-obsoleted due to no activity on 2024/11/10 05:27
linux-4.14 BUG: soft lockup in tcp_write_timer 1 2 2286d 2365d 0/1 auto-closed as invalid on 2020/09/05 12:42
upstream BUG: soft lockup in tcp_write_timer net 1 11 2565d 2573d 0/29 auto-closed as invalid on 2019/10/25 14:11
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/05/19 14:19 28m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (2)
Created Duration User Patch Repo Result
2026/03/31 14:52 1m fix candidate upstream error job log
2026/03/01 10:21 1m fix candidate upstream error job log

Sample crash report:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10500 ticks this GP) idle=a61/1/0x4000000000000000 softirq=22023/22023 fqs=0 
	(t=10500 jiffies g=23193 q=426)
rcu: rcu_preempt kthread timer wakeup didn't happen for 10499 jiffies! g23193 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=1 timer-softirq=15497
rcu: rcu_preempt kthread starved for 10500 jiffies! g23193 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
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:I stack:27984 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 1
CPU: 1 PID: 3562 Comm: udevd 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_cpu_stall+0x318/0x5f0 kernel/rcu/tree_stall.h:631
 check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x6ea/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+0x4ad/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+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1108
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
RIP: 0010:arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
RIP: 0010:kvm_wait+0x159/0x1b0 arch/x86/kernel/kvm.c:918
Code: 89 df 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0 75 4b 0f b6 1f e8 a7 b4 4a 00 44 38 e3 75 10 66 90 0f 00 2d 99 e2 f3 08 fb f4 <e9> 16 ff ff ff fb e9 10 ff ff ff e8 47 8f 87 08 89 f9 80 e1 07 38
RSP: 0018:ffffc90000dd08c0 EFLAGS: 00000246
RAX: 88eb4aa7da4ab700 RBX: 0000000000000003 RCX: 88eb4aa7da4ab700
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: ffffffff8a79f800
RBP: ffffc90000dd0970 R08: ffffffff901d315f R09: 1ffffffff203a62b
R10: dffffc0000000000 R11: fffffbfff203a62c R12: 0000000000000003
R13: ffff8880b913b154 R14: dffffc0000000000 R15: 1ffff920001ba118
 pv_wait arch/x86/include/asm/paravirt.h:597 [inline]
 pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:470 [inline]
 __pv_queued_spin_lock_slowpath+0x60f/0x9c0 kernel/locking/qspinlock.c:508
 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:585 [inline]
 queued_spin_lock_slowpath+0x43/0x50 arch/x86/include/asm/qspinlock.h:51
 queued_spin_lock include/asm-generic/qspinlock.h:85 [inline]
 do_raw_spin_lock+0x265/0x2f0 kernel/locking/spinlock_debug.c:115
 spin_lock include/linux/spinlock.h:364 [inline]
 tcp_write_timer+0x29/0x280 net/ipv4/tcp_timer.c:673
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
 expire_timers kernel/time/timer.c:1699 [inline]
 __run_timers+0x53e/0x800 kernel/time/timer.c:1970
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
 handle_softirqs+0x339/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 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:lock_release+0x5a4/0x8a0 kernel/locking/lockdep.c:5647
Code: 80 00 00 00 f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 2c 04 f8 75 6f 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 2c 00 00 00 00 43 c7 44 2c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc90002e0f740 EFLAGS: 00000206
RAX: 0000000000000001 RBX: ffffffffffffffff RCX: 88eb4aa7da4ab700
RDX: 0000000000000000 RSI: ffffffff8a2b3a20 RDI: ffffffff8a79f800
RBP: ffffc90002e0f858 R08: ffffffff8d89dc2f R09: 1ffffffff1b13b85
R10: dffffc0000000000 R11: fffffbfff1b13b86 R12: 1ffff920005c1ef4
R13: dffffc0000000000 R14: ffff88807d0ea8a0 R15: 0000000000000246
 rcu_read_unlock include/linux/rcupdate.h:773 [inline]
 aa_get_task_label+0x21c/0x2c0 security/apparmor/task.c:30
 apparmor_task_getsecid+0x25/0x120 security/apparmor/lsm.c:733
 security_task_getsecid_subj+0x5f/0xc0 security/security.c:1847
 ima_file_check+0x89/0x110 security/integrity/ima/ima_main.c:532
 do_open fs/namei.c:3618 [inline]
 path_openat+0x27a8/0x2fa0 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: 0033:0x7fd63e347407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffefb8c7450 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fd63e259880 RCX: 00007fd63e347407
RDX: 0000000000080141 RSI: 0000562c6368902e RDI: ffffffffffffff9c
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000001a4 R11: 0000000000000202 R12: 00000000ffffffff
R13: 00000000ffffffff R14: ffffffffffffffff R15: 0000000000000000
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 154 Comm: kworker/u4:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: bat_events batadv_nc_worker
RIP: 0010:unwind_next_frame+0x29/0x1d90 arch/x86/kernel/unwind_orc.c:424
Code: 90 55 41 57 41 56 41 55 41 54 53 48 81 ec 88 00 00 00 48 89 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 63 21 89 00 4c 8b
RSP: 0018:ffffc90000006d00 EFLAGS: 00000802
RAX: 1ffff92000000dd9 RBX: ffffc90000006e80 RCX: 0000000000000101
RDX: ffffc90000007690 RSI: dffffc0000000000 RDI: ffffc90000006e80
RBP: ffffc90000006ec8 R08: ffffc90000006edf R09: ffffc90000006ed0
R10: dffffc0000000000 R11: fffff52000000ddc R12: ffffc90000006eb8
R13: ffffc90000006e90 R14: dffffc0000000000 R15: ffffc90000006e88
FS:  0000000000000000(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000100000000 CR3: 000000000c08e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __unwind_start+0x5bb/0x740 arch/x86/kernel/unwind_orc.c:704
 unwind_start arch/x86/include/asm/unwind.h:60 [inline]
 perf_callchain_kernel+0x2f0/0x720 arch/x86/events/core.c:-1
 get_perf_callchain+0x356/0x460 kernel/events/callchain.c:200
 perf_callchain kernel/events/core.c:7606 [inline]
 perf_prepare_sample+0x352/0x1cd0 kernel/events/core.c:7633
 __perf_event_output kernel/events/core.c:7802 [inline]
 perf_event_output_forward+0x185/0x2e0 kernel/events/core.c:7822
 __perf_event_overflow+0x364/0x530 kernel/events/core.c:9515
 perf_tp_event+0x383/0xbf0 kernel/events/core.c:10047
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10021
 perf_trace_preemptirq_template+0x2aa/0x360 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle+0x108/0x180 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x57/0x80 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 e2 f0 9c 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007780 EFLAGS: 00000206
RAX: 0d64f59019d69c00 RBX: 1ffff92000000ef4 RCX: 0d64f59019d69c00
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: ffffffff8a79f800
RBP: ffffc90000007860 R08: ffffffff901d315f R09: 1ffffffff203a62b
R10: dffffc0000000000 R11: fffffbfff203a62c R12: ffffffff8c322f00
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 __ip_queue_xmit+0x1242/0x1c00 net/ipv4/ip_output.c:539
 __tcp_transmit_skb+0x1d11/0x3200 net/ipv4/tcp_output.c:1404
 tcp_delack_timer_handler+0x32e/0x730 net/ipv4/tcp_timer.c:314
 tcp_delack_timer+0x188/0x2e0 net/ipv4/tcp_timer.c:341
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
 expire_timers kernel/time/timer.c:1699 [inline]
 __run_timers+0x53e/0x800 kernel/time/timer.c:1970
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
 handle_softirqs+0x339/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 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:should_resched arch/x86/include/asm/preempt.h:103 [inline]
RIP: 0010:__local_bh_enable_ip+0x13e/0x1c0 kernel/softirq.c:408
Code: 8a e8 a6 fc 72 08 65 66 8b 05 ae 5b ba 7e 66 85 c0 75 54 bf 01 00 00 00 e8 bf 24 09 00 e8 9a 10 36 00 fb 65 8b 05 5a 32 b9 7e <85> c0 75 05 e8 a9 3f b7 ff 48 c7 04 24 0e 36 e0 45 4b c7 04 37 00
RSP: 0018:ffffc90002017aa0 EFLAGS: 00000286
RAX: 0000000080000000 RBX: 0000000000000201 RCX: 0d64f59019d69c00
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: ffffffff8a79f800
RBP: ffffc90002017b38 R08: ffffffff901d31c7 R09: 1ffffffff203a638
R10: dffffc0000000000 R11: fffffbfff203a639 R12: ffffffff89912aa6
R13: dffffc0000000000 R14: dffffc0000000000 R15: 1ffff92000402f54
 spin_unlock_bh include/linux/spinlock.h:409 [inline]
 batadv_nc_purge_paths+0x316/0x3b0 net/batman-adv/network-coding.c:475
 batadv_nc_worker+0x2e7/0x5c0 net/batman-adv/network-coding.c:724
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
NMI backtrace for cpu 1
CPU: 1 PID: 3562 Comm: udevd 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_dump_cpu_stacks+0x22f/0x380 kernel/rcu/tree_stall.h:349
 print_cpu_stall+0x31d/0x5f0 kernel/rcu/tree_stall.h:633
 check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x6ea/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+0x4ad/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+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1108
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
RIP: 0010:arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
RIP: 0010:kvm_wait+0x159/0x1b0 arch/x86/kernel/kvm.c:918
Code: 89 df 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0 75 4b 0f b6 1f e8 a7 b4 4a 00 44 38 e3 75 10 66 90 0f 00 2d 99 e2 f3 08 fb f4 <e9> 16 ff ff ff fb e9 10 ff ff ff e8 47 8f 87 08 89 f9 80 e1 07 38
RSP: 0018:ffffc90000dd08c0 EFLAGS: 00000246
RAX: 88eb4aa7da4ab700 RBX: 0000000000000003 RCX: 88eb4aa7da4ab700
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: ffffffff8a79f800
RBP: ffffc90000dd0970 R08: ffffffff901d315f R09: 1ffffffff203a62b
R10: dffffc0000000000 R11: fffffbfff203a62c R12: 0000000000000003
R13: ffff8880b913b154 R14: dffffc0000000000 R15: 1ffff920001ba118
 pv_wait arch/x86/include/asm/paravirt.h:597 [inline]
 pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:470 [inline]
 __pv_queued_spin_lock_slowpath+0x60f/0x9c0 kernel/locking/qspinlock.c:508
 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:585 [inline]
 queued_spin_lock_slowpath+0x43/0x50 arch/x86/include/asm/qspinlock.h:51
 queued_spin_lock include/asm-generic/qspinlock.h:85 [inline]
 do_raw_spin_lock+0x265/0x2f0 kernel/locking/spinlock_debug.c:115
 spin_lock include/linux/spinlock.h:364 [inline]
 tcp_write_timer+0x29/0x280 net/ipv4/tcp_timer.c:673
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
 expire_timers kernel/time/timer.c:1699 [inline]
 __run_timers+0x53e/0x800 kernel/time/timer.c:1970
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
 handle_softirqs+0x339/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 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:lock_release+0x5a4/0x8a0 kernel/locking/lockdep.c:5647
Code: 80 00 00 00 f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 2c 04 f8 75 6f 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 2c 00 00 00 00 43 c7 44 2c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc90002e0f740 EFLAGS: 00000206
RAX: 0000000000000001 RBX: ffffffffffffffff RCX: 88eb4aa7da4ab700
RDX: 0000000000000000 RSI: ffffffff8a2b3a20 RDI: ffffffff8a79f800
RBP: ffffc90002e0f858 R08: ffffffff8d89dc2f R09: 1ffffffff1b13b85
R10: dffffc0000000000 R11: fffffbfff1b13b86 R12: 1ffff920005c1ef4
R13: dffffc0000000000 R14: ffff88807d0ea8a0 R15: 0000000000000246
 rcu_read_unlock include/linux/rcupdate.h:773 [inline]
 aa_get_task_label+0x21c/0x2c0 security/apparmor/task.c:30
 apparmor_task_getsecid+0x25/0x120 security/apparmor/lsm.c:733
 security_task_getsecid_subj+0x5f/0xc0 security/security.c:1847
 ima_file_check+0x89/0x110 security/integrity/ima/ima_main.c:532
 do_open fs/namei.c:3618 [inline]
 path_openat+0x27a8/0x2fa0 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: 0033:0x7fd63e347407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffefb8c7450 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fd63e259880 RCX: 00007fd63e347407
RDX: 0000000000080141 RSI: 0000562c6368902e RDI: ffffffffffffff9c
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000001a4 R11: 0000000000000202 R12: 00000000ffffffff
R13: 00000000ffffffff R14: ffffffffffffffff R15: 0000000000000000
 </TASK>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/01 05:58 linux-5.15.y 3330a8d33e08 43249bac .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in tcp_write_timer
2026/04/01 18:07 linux-5.15.y 91d48252ad4b 9a1f7828 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in tcp_write_timer
2026/03/12 00:07 linux-5.15.y 91d48252ad4b 2d88ab01 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in tcp_write_timer
2026/05/21 15:19 linux-5.15.y 93741761e5e3 e195359d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf BUG: soft lockup in tcp_write_timer
* Struck through repros no longer work on HEAD.