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: 202d, last: 83d
▶ ▼ 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 2060d 2115d 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 801d 801d 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 710d 762d 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 2609d 2604d 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 495d 579d 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 1927d 1927d 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 596d 825d 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 810d 835d 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 4 126d 207d 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 344d 360d 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 13d 198d 0/2 upstream: reported on 2026/03/10 11:19
linux-4.14 INFO: rcu detected stall in tcp_write_timer 1 4 2211d 2454d 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 2340d 2394d 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 196d 226d 0/29 closed as invalid on 2026/03/27 01:43
linux-4.19 BUG: soft lockup in tcp_write_timer (3) 1 2 1363d 1376d 0/1 upstream: reported on 2022/12/17 21:41
linux-4.19 BUG: soft lockup in tcp_write_timer (2) 1 2 1773d 1836d 0/1 auto-closed as invalid on 2022/03/16 10:56
android-54 BUG: soft lockup in tcp_write_timer 1 1 508d 508d 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 2002d 2002d 0/1 auto-closed as invalid on 2021/07/30 14:52
upstream BUG: soft lockup in tcp_write_timer (9) net 1 2 290d 294d 0/29 closed as invalid on 2026/01/07 12:42
upstream BUG: soft lockup in tcp_write_timer (2) kvm 1 1 1612d 1612d 0/29 auto-closed as invalid on 2022/06/24 22:31
upstream BUG: soft lockup in tcp_write_timer (3) net 1 6 989d 1097d 0/29 closed as invalid on 2024/03/18 17:07
upstream BUG: soft lockup in tcp_write_timer (7) net 1 1 375d 375d 0/29 closed as invalid on 2025/09/29 07:16
upstream BUG: soft lockup in tcp_write_timer (8) mm 1 1 351d 351d 0/29 closed as invalid on 2025/11/04 11:28
upstream BUG: soft lockup in tcp_write_timer (6) bpf 1 1 423d 423d 0/29 closed as invalid on 2025/09/01 08:24
upstream BUG: soft lockup in tcp_write_timer (5) mm net 1 8 479d 540d 0/29 closed as invalid on 2025/07/11 15:27
android-5-15 BUG: soft lockup in tcp_write_timer 1 11 773d 886d 0/2 auto-obsoleted due to no activity on 2024/11/10 05:27

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { P28101 1-.... } 2828 jiffies s: 102477 root: 0x2/T
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 28101 Comm: syz.1.8059 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:__lock_release kernel/locking/lockdep.c:5348 [inline]
RIP: 0010:lock_release+0x253/0x920 kernel/locking/lockdep.c:5682
Code: e4 0f 84 03 03 00 00 4d 8d 74 24 24 4c 89 f0 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 bb 04 00 00 41 83 3e 00 0f 85 cc 03 00 00 <4d> 8d 74 24 20 4c 89 f3 48 c1 eb 03 42 0f b6 04 2b 84 c0 4c 8b 7c
RSP: 0018:ffffc900001dfba0 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000023 RCX: 0000000000000001
RDX: 0000000000000007 RSI: ffffffff8cb2db60 RDI: ffff88807660e5f8
RBP: ffffc900001dfcb0 R08: ffffffff8e2123ef R09: 1ffffffff1c4247d
R10: dffffc0000000000 R11: fffffbfff1c4247e R12: ffff88807660e5f8
R13: dffffc0000000000 R14: ffff88807660e61c R15: 0000000000000007
FS:  00007f83769fd6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd87571c90 CR3: 00000000611dd000 CR4: 00000000003506e0
DR0: 0000000000008d24 DR1: 0000000000008d24 DR2: 0000200000000300
DR3: 0000200000000300 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 __perf_output_begin kernel/events/ring_buffer.c:263 [inline]
 perf_output_begin_forward+0x7e4/0xa70 kernel/events/ring_buffer.c:272
 __perf_event_output kernel/events/core.c:7732 [inline]
 perf_event_output_forward+0x1ad/0x2f0 kernel/events/core.c:7750
 __perf_event_overflow+0x457/0x630 kernel/events/core.c:9496
 perf_event_overflow kernel/events/core.c:9517 [inline]
 perf_swevent_hrtimer+0x472/0x630 kernel/events/core.c:10967
 __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:on_stack arch/x86/include/asm/stacktrace.h:56 [inline]
RIP: 0010:stack_access_ok arch/x86/kernel/unwind_orc.c:351 [inline]
RIP: 0010:deref_stack_reg arch/x86/kernel/unwind_orc.c:357 [inline]
RIP: 0010:unwind_next_frame+0x805/0x1fd0 arch/x86/kernel/unwind_orc.c:539
Code: f4 ff 85 c0 0f 85 55 0f 00 00 49 bc 00 00 00 00 00 fc ff df 43 80 3c 27 00 4c 8d 7b 08 74 08 4c 89 ff e8 2e 46 9a 00 4d 8b 3f <43> 80 3c 26 00 4c 8b 6c 24 10 74 09 48 8d 7b 10 e8 16 46 9a 00 4c
RSP: 0018:ffffc900001e0540 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffffc900001e05e8 RCX: 0000000000000001
RDX: 0000000000000002 RSI: ffffc90004c30000 RDI: ffffc90004c2f0f0
RBP: ffffc90004c2f0f0 R08: 0000000000000001 R09: 000000000000000f
R10: dffffc0000000000 R11: fffff5200003c0c9 R12: dffffc0000000000
R13: ffffc900001e1000 R14: 1ffff9200003c0bf R15: ffffc90004c28000
 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:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x133/0x1b0 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 kmem_cache_free+0xf7/0x2a0 mm/slub.c:3709
 tcp_write_queue_purge+0x13c/0x300 net/ipv4/tcp.c:3123
 tcp_done_with_error+0x3f/0xc0 net/ipv4/tcp_input.c:4408
 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:preempt_schedule_irq+0xb6/0x160 kernel/sched/core.c:6874
Code: 00 00 43 c6 44 37 04 f8 74 0b 0f 0b 48 f7 03 08 00 00 00 74 7f bf 01 00 00 00 e8 b5 ef 1f f7 e8 d0 ba 4f f7 fb bf 01 00 00 00 <e8> 25 ba ff ff 43 c6 44 37 08 00 48 c7 44 24 40 00 00 00 00 9c 8f
RSP: 0018:ffffc90004c2f1a0 EFLAGS: 00000286
RAX: 1758c520ad74df00 RBX: 0000000000000000 RCX: 1758c520ad74df00
RDX: dffffc0000000000 RSI: ffffffff8a8c17a0 RDI: 0000000000000001
RBP: ffffc90004c2f250 R08: ffffffff90b1024f R09: 1ffffffff2162049
R10: dffffc0000000000 R11: fffffbfff216204a R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 1ffff92000985e34
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__sanitizer_cov_trace_pc+0x41/0x60 kernel/kcov.c:221
Code: ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 1c 16 00 00 00 74 2c 8b 91 f8 15 00 00 83 fa 02 75 21 48 8b 91 00 16 00 00 48 8b 32 <48> 8d 7e 01 8b 89 fc 15 00 00 48 39 cf 73 08 48 89 3a 48 89 44 f2
RSP: 0018:ffffc90004c2f318 EFLAGS: 00000246
RAX: ffffffff81dbf5b5 RBX: ffff88807660df70 RCX: ffff88807660da00
RDX: ffffc9001c1ae000 RSI: 000000000000269e RDI: 0000000000000000
RBP: ffffc90004c2f450 R08: 0000000000002800 R09: ffff88823b400000
R10: 000000003f4912cf R11: 00000000fafb55a4 R12: dffffc0000000000
R13: 1ffff1100ecc1bee R14: 0000000005d90397 R15: 1ffff92000985e68
 save_stack+0x145/0x230 mm/page_owner.c:129
 __reset_page_owner+0x51/0x190 mm/page_owner.c:148
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1487 [inline]
 free_pcp_prepare mm/page_alloc.c:1537 [inline]
 free_unref_page_prepare+0x8e5/0x9e0 mm/page_alloc.c:3414
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3509
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x490 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 slab_alloc mm/slub.c:3367 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3374 [inline]
 kmem_cache_alloc+0x18b/0x2f0 mm/slub.c:3383
 kmem_cache_zalloc include/linux/slab.h:689 [inline]
 __kernfs_new_node+0xe1/0x7f0 fs/kernfs/dir.c:614
 kernfs_new_node+0x148/0x250 fs/kernfs/dir.c:690
 __kernfs_create_file+0x47/0x2e0 fs/kernfs/file.c:1068
 sysfs_add_file_mode_ns+0x233/0x2f0 fs/sysfs/file.c:294
 create_files fs/sysfs/group.c:64 [inline]
 internal_create_group+0x490/0xce0 fs/sysfs/group.c:148
 internal_create_groups fs/sysfs/group.c:188 [inline]
 sysfs_create_groups+0x55/0x120 fs/sysfs/group.c:214
 device_add_groups drivers/base/core.c:2752 [inline]
 device_add_attrs+0x1ae/0x830 drivers/base/core.c:2911
 device_add+0x677/0x1050 drivers/base/core.c:3648
 netdev_register_kobject+0x184/0x320 net/core/net-sysfs.c:2013
 register_netdevice+0x133a/0x1b80 net/core/dev.c:10243
 ppp_unit_register drivers/net/ppp/ppp_generic.c:1232 [inline]
 ppp_dev_configure+0x875/0xad0 drivers/net/ppp/ppp_generic.c:1288
 ppp_create_interface drivers/net/ppp/ppp_generic.c:3365 [inline]
 ppp_unattached_ioctl drivers/net/ppp/ppp_generic.c:1073 [inline]
 ppp_ioctl+0x8c2/0x1a40 drivers/net/ppp/ppp_generic.c:743
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 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: 0033:0x7f8375b9de59
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:00007f83769fd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f8375e25fa0 RCX: 00007f8375b9de59
RDX: 000000110e22fff6 RSI: 00000000c004743e RDI: 0000000000000004
RBP: 00007f8375c33e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8375e26038 R14: 00007f8375e25fa0 R15: 00007ffdc77573b8
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.