INFO: rcu detected stall in tcp_write_timer (2)

Status: upstream: reported on 2026/03/06 03:16
Reported-by: syzbot+8e8fec64822c9c0eb31a@syzkaller.appspotmail.com
First crash: 217d, last: 2d05h
▶ ▼ Similar bugs (26)
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 2075d 2130d 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 816d 816d 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 725d 777d 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 2624d 2619d 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 510d 594d 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 1942d 1942d 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 611d 840d 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 825d 850d 26/29 fixed on 2024/07/09 19:14
linux-5.15 INFO: rcu detected stall in tcp_write_timer (4) origin:lts-only 1 syz error 6 14m 222d 0/3 upstream: reported syz repro on 2026/03/01 05:59
linux-5.15 INFO: rcu detected stall in tcp_write_timer (3) 1 2 360d 375d 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 8 28d 213d 0/2 upstream: reported on 2026/03/10 11:19
linux-4.14 INFO: rcu detected stall in tcp_write_timer 1 4 2226d 2469d 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 2355d 2409d 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 211d 241d 0/29 closed as invalid on 2026/03/27 01:43
linux-4.19 BUG: soft lockup in tcp_write_timer (3) 1 2 1378d 1391d 0/1 upstream: reported on 2022/12/17 21:41
linux-4.19 BUG: soft lockup in tcp_write_timer (2) 1 2 1788d 1852d 0/1 auto-closed as invalid on 2022/03/16 10:56
android-54 BUG: soft lockup in tcp_write_timer 1 1 523d 523d 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 2017d 2017d 0/1 auto-closed as invalid on 2021/07/30 14:52
upstream BUG: soft lockup in tcp_write_timer (9) net 1 2 305d 309d 0/29 closed as invalid on 2026/01/07 12:42
upstream BUG: soft lockup in tcp_write_timer (2) kvm 1 1 1627d 1627d 0/29 auto-closed as invalid on 2022/06/24 22:31
upstream BUG: soft lockup in tcp_write_timer (3) net 1 6 1004d 1112d 0/29 closed as invalid on 2024/03/18 17:07
upstream BUG: soft lockup in tcp_write_timer (7) net 1 1 390d 390d 0/29 closed as invalid on 2025/09/29 07:16
upstream BUG: soft lockup in tcp_write_timer (8) mm 1 1 366d 366d 0/29 closed as invalid on 2025/11/04 11:28
upstream BUG: soft lockup in tcp_write_timer (6) bpf 1 1 438d 438d 0/29 closed as invalid on 2025/09/01 08:24
upstream BUG: soft lockup in tcp_write_timer (5) mm net 1 8 494d 556d 0/29 closed as invalid on 2025/07/11 15:27
android-5-15 BUG: soft lockup in tcp_write_timer 1 11 788d 901d 0/2 auto-obsoleted due to no activity on 2024/11/10 05:27

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P3764/1:b..l
	(detected by 1, t=10502 jiffies, g=403621, q=2472 ncpus=2)
task:syz.0.20998     state:R  running task     stack:24216 pid:3764  ppid:1364   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5246 [inline]
 __schedule+0x107f/0x4030 kernel/sched/core.c:6563
 preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6732
 preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6756
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
 __local_bh_enable_ip+0x147/0x1c0 kernel/softirq.c:428
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:861 [inline]
 __dev_queue_xmit+0x1d84/0x3810 net/core/dev.c:4411
 dev_queue_xmit include/linux/netdevice.h:3056 [inline]
 __bpf_tx_skb net/core/filter.c:2143 [inline]
 __bpf_redirect_no_mac net/core/filter.c:2177 [inline]
 __bpf_redirect+0x8c7/0x1110 net/core/filter.c:2200
 ____bpf_clone_redirect net/core/filter.c:2482 [inline]
 bpf_clone_redirect+0x311/0x4a0 net/core/filter.c:2445
 bpf_prog_973cd02a7a0e8181+0x56/0x5b
 bpf_dispatcher_nop_func include/linux/bpf.h:1013 [inline]
 __bpf_prog_run include/linux/filter.h:597 [inline]
 bpf_prog_run include/linux/filter.h:615 [inline]
 bpf_test_run+0x4c1/0x830 net/bpf/test_run.c:402
 bpf_prog_test_run_skb+0xdaf/0x18e0 net/bpf/test_run.c:1222
 bpf_prog_test_run+0x31c/0x390 kernel/bpf/syscall.c:3695
 __sys_bpf+0x62b/0x780 kernel/bpf/syscall.c:5053
 __do_sys_bpf kernel/bpf/syscall.c:5139 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5137 [inline]
 __x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:5137
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f667cf9e199
RSP: 002b:00007f667de4a028 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f667d225fa0 RCX: 00007f667cf9e199
RDX: 000000000000002c RSI: 0000200000000080 RDI: 000000000000000a
RBP: 00007f667d0358e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f667d226038 R14: 00007f667d225fa0 R15: 00007ffffeff93d8
 </TASK>
rcu: rcu_preempt kthread starved for 10477 jiffies! g403621 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:26768 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5246 [inline]
 __schedule+0x107f/0x4030 kernel/sched/core.c:6563
 schedule+0xb9/0x180 kernel/sched/core.c:6639
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x303/0x1350 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </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 PID: 3766 Comm: syz.1.21000 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:strlen+0x2a/0x60 lib/string.c:502
Code: 41 57 41 56 41 54 53 48 c7 c0 ff ff ff ff 49 be 00 00 00 00 00 fc ff df 48 89 fb 49 89 c7 48 89 d8 48 c1 e8 03 42 0f b6 04 30 <84> c0 75 11 48 ff c3 49 8d 47 01 42 80 7c 3f 01 00 75 de eb 19 89
RSP: 0018:ffffc90000006f58 EFLAGS: 00000807
RAX: 0000000000000000 RBX: ffffffff8a8e0f47 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8cb46fc8 RDI: ffffffff8a8e0f40
RBP: ffffc90000007080 R08: 0000000000000002 R09: 0000000000000001
R10: dffffc0000000000 R11: fffffbfff1c41b2e R12: ffffffff8c9f9640
R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000006
FS:  00007ff866f8d6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f54079dfff8 CR3: 0000000063f9e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000200000000300
DR3: 0000200000000300 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 __fortify_strlen include/linux/fortify-string.h:196 [inline]
 trace_event_get_offsets_lock_acquire include/trace/events/lock.h:34 [inline]
 perf_trace_lock_acquire+0xd9/0x3f0 include/trace/events/lock.h:24
 trace_lock_acquire include/trace/events/lock.h:24 [inline]
 lock_acquire+0x452/0x4a0 kernel/locking/lockdep.c:5761
 seqcount_lockdep_reader_access+0xcd/0x1d0 include/linux/seqlock.h:102
 ktime_get+0x31/0x270 kernel/time/timekeeping.c:846
 hrtimer_forward_now include/linux/hrtimer.h:509 [inline]
 perf_swevent_hrtimer+0x4f8/0x630 kernel/events/core.c:10982
 __run_hrtimer kernel/time/hrtimer.c:1751 [inline]
 __hrtimer_run_queues+0x4e7/0xc90 kernel/time/hrtimer.c:1815
 hrtimer_interrupt+0x399/0x980 kernel/time/hrtimer.c:1877
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
 __sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1118
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> bf e8 1a f7 65 8b 05 80 98 c4 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc90000007880 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a02 RCX: c9ab7842d3dc7e00
RDX: dffffc0000000000 RSI: ffffffff8a8c18a0 RDI: 0000000000000001
RBP: ffffc90000007908 R08: ffffffff90b33307 R09: 1ffffffff2166660
R10: dffffc0000000000 R11: fffffbfff2166661 R12: dffffc0000000000
R13: ffff888072b70fc0 R14: ffffffff96ec66b0 R15: 1ffff92000000f10
 debug_object_assert_init+0x1ed/0x300 lib/debugobjects.c:946
 debug_timer_assert_init kernel/time/timer.c:792 [inline]
 debug_assert_init kernel/time/timer.c:837 [inline]
 __timer_delete+0x3f/0x220 kernel/time/timer.c:1321
 del_timer include/linux/timer.h:213 [inline]
 sk_stop_timer+0x17/0x80 net/core/sock.c:3397
 tcp_clear_xmit_timers include/net/tcp.h:669 [inline]
 tcp_v4_destroy_sock+0x181/0x760 net/ipv4/tcp_ipv4.c:2276
 inet_csk_destroy_sock+0x15c/0x350 net/ipv4/inet_connection_sock.c:1241
 tcp_done_with_error+0x47/0xc0 net/ipv4/tcp_input.c:4409
 tcp_write_err net/ipv4/tcp_timer.c:70 [inline]
 tcp_write_timeout net/ipv4/tcp_timer.c:273 [inline]
 tcp_retransmit_timer+0x1299/0x27c0 net/ipv4/tcp_timer.c:547
 tcp_write_timer+0x126/0x280 net/ipv4/tcp_timer.c:676
 call_timer_fn+0x1ac/0x670 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x56c/0x810 kernel/time/timer.c:2023
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2036
 handle_softirqs+0x291/0x910 kernel/softirq.c:596
 __do_softirq kernel/softirq.c:630 [inline]
 invoke_softirq kernel/softirq.c:470 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:kasan_mem_to_shadow include/linux/kasan.h:59 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:129 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:159 [inline]
RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline]
RIP: 0010:kasan_check_range+0x5a/0x290 mm/kasan/generic.c:189
Code: 01 00 00 49 bc 01 00 00 00 00 fc ff df 49 89 fe 49 c1 ee 03 49 ba 00 00 00 00 00 fc ff df 4f 8d 1c 16 4c 8d 44 3e ff 4d 89 c1 <49> c1 e9 03 4b 8d 1c 21 49 89 df 4d 29 df 49 83 ff 10 7f 29 4d 85
RSP: 0018:ffffc90003cb6610 EFLAGS: 00000a02
RAX: ffffffff8a24d901 RBX: 0000000000000018 RCX: ffffffff8a24da05
RDX: 0000000000000001 RSI: 0000000000000018 RDI: ffffc90003cb66e0
RBP: 0000000000000000 R08: ffffc90003cb66f7 R09: ffffc90003cb66f7
R10: dffffc0000000000 R11: fffff52000796cdc R12: dffffc0000000001
R13: 0000000000000cdc R14: 1ffff92000796cdc R15: ffff0a0000000509
 memset+0x1e/0x40 mm/kasan/shadow.c:44
 number+0x285/0xef0 lib/vsprintf.c:458
 vsnprintf+0x12d3/0x1c20 lib/vsprintf.c:2871
 sprintf+0xe4/0x140 lib/vsprintf.c:3009
 print_time kernel/printk/printk.c:1274 [inline]
 info_print_prefix+0x168/0x360 kernel/printk/printk.c:1300
 record_print_text+0x17e/0x4a0 kernel/printk/printk.c:1349
 console_emit_next_record+0x5a4/0xb50 kernel/printk/printk.c:2760
 console_flush_all kernel/printk/printk.c:-1 [inline]
 console_unlock+0x223/0x630 kernel/printk/printk.c:2906
 vprintk_emit+0x4b3/0x6a0 kernel/printk/printk.c:2303
 _printk+0xda/0x130 kernel/printk/printk.c:2328
 __nla_validate_parse+0x20c1/0x2970 lib/nlattr.c:625
 __nla_validate+0x3c/0x50 lib/nlattr.c:655
 nlmsg_validate_deprecated include/net/netlink.h:886 [inline]
 rtm_to_fib_config+0x88/0x1370 net/ipv4/fib_frontend.c:736
 inet_rtm_newroute+0x112/0x230 net/ipv4/fib_frontend.c:907
 rtnetlink_rcv_msg+0x863/0xfb0 net/core/rtnetlink.c:6166
 netlink_rcv_skb+0x1ef/0x440 net/netlink/af_netlink.c:2516
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x7ad/0x920 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8ad/0xbd0 net/netlink/af_netlink.c:1877
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 ____sys_sendmsg+0x5ed/0x9a0 net/socket.c:2519
 ___sys_sendmsg+0x2a2/0x360 net/socket.c:2573
 __sys_sendmsg net/socket.c:2602 [inline]
 __do_sys_sendmsg net/socket.c:2611 [inline]
 __se_sys_sendmsg+0x1c3/0x2b0 net/socket.c:2609
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ff86619e199
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:00007ff866f8d028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007ff866426090 RCX: 00007ff86619e199
RDX: 0000000000000000 RSI: 0000200000000940 RDI: 000000000000000a
RBP: 00007ff8662358e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff866426128 R14: 00007ff866426090 R15: 00007fff5508ef08
 </TASK>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/07 14:30 linux-6.1.y a500ba24937a 6520ecdb .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in tcp_write_timer
2026/07/03 12:51 linux-6.1.y fdb6fcb41cc7 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in tcp_write_timer
2026/04/23 01:41 linux-6.1.y 7c87defbd336 b10da5ec .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in tcp_write_timer
2026/03/06 03:15 linux-6.1.y f2ddafa93a25 31e9c887 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in tcp_write_timer
* Struck through repros no longer work on HEAD.