INFO: rcu detected stall in tcp_write_timer

Status: auto-closed as invalid on 2021/01/02 05:45
Reported-by: syzbot+375bc096ce55c9a34210@syzkaller.appspotmail.com
First crash: 2418d, last: 2175d
▶ ▼ Similar bugs (13)
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 2024d 2080d 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 765d 765d 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 674d 727d 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 2573d 2568d 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 460d 544d 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 1891d 1891d 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 560d 790d 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 775d 799d 26/29 fixed on 2024/07/09 19:14
linux-6.1 INFO: rcu detected stall in tcp_write_timer (2) 1 3 47d 167d 0/3 upstream: reported on 2026/03/06 03:16
linux-5.15 INFO: rcu detected stall in tcp_write_timer (4) origin:lts-only 1 syz error 4 90d 171d 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 309d 324d 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 32d 162d 0/2 upstream: reported on 2026/03/10 11:19
linux-4.19 INFO: rcu detected stall in tcp_write_timer 1 2 2304d 2358d 0/1 auto-closed as invalid on 2020/08/26 06:46

Sample crash report:
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.2'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor.5'.
ip6_tunnel: ip6gretap0 xmit: Local address not yet configured!
INFO: rcu_preempt self-detected stall on CPU
	1-...: (10500 ticks this GP) idle=f32/140000000000002/0 softirq=18491/18491 fqs=0 
	 (t=10500 jiffies g=3842 c=3841 q=386)
rcu_preempt kthread starved for 10500 jiffies! g3842 c3841 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=1
rcu_preempt     R  running task    30008     8      2 0x80000000
Call Trace:
 context_switch kernel/sched/core.c:2808 [inline]
 __schedule+0x88b/0x1de0 kernel/sched/core.c:3384
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 schedule_timeout+0x4af/0xe90 kernel/time/timer.c:1754
 rcu_gp_kthread+0xc0a/0x1e60 kernel/rcu/tree.c:2255
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
NMI backtrace for cpu 1
CPU: 1 PID: 10447 Comm: syz-executor.1 Not tainted 4.14.196-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 nmi_cpu_backtrace.cold+0x57/0x93 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x13a/0x17f lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:158 [inline]
 rcu_dump_cpu_stacks+0x15f/0x19c kernel/rcu/tree.c:1396
 print_cpu_stall kernel/rcu/tree.c:1542 [inline]
 check_cpu_stall kernel/rcu/tree.c:1610 [inline]
 __rcu_pending kernel/rcu/tree.c:3390 [inline]
 rcu_pending kernel/rcu/tree.c:3452 [inline]
 rcu_check_callbacks.cold+0x464/0xd99 kernel/rcu/tree.c:2792
 update_process_times+0x28/0xa0 kernel/time/timer.c:1591
 tick_sched_handle+0x7d/0x150 kernel/time/tick-sched.c:165
 tick_sched_timer+0x92/0x200 kernel/time/tick-sched.c:1223
 __run_hrtimer kernel/time/hrtimer.c:1223 [inline]
 __hrtimer_run_queues+0x30b/0xc80 kernel/time/hrtimer.c:1287
 hrtimer_interrupt+0x1e6/0x5e0 kernel/time/hrtimer.c:1321
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1075 [inline]
 smp_apic_timer_interrupt+0x117/0x5e0 arch/x86/kernel/apic/apic.c:1100
 apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:793
RIP: 0010:kfree+0x0/0x250 mm/slab.c:3801
RSP: 0018:ffff8880aeb07bb8 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff10
RAX: ffff888058786000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000100 RSI: ffff8880a495b60c RDI: ffff88803ff52c00
RBP: ffff88803ff53ac3 R08: ffffea0000ffd000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88803ff52c00
R13: ffff88803ff53ac0 R14: ffff88803ff53b10 R15: ffffea0000ffd61c
 skb_free_head net/core/skbuff.c:554 [inline]
 skb_release_data+0x5f6/0x820 net/core/skbuff.c:574
 skb_release_all net/core/skbuff.c:631 [inline]
 __kfree_skb+0x46/0x60 net/core/skbuff.c:645
 sk_wmem_free_skb include/net/sock.h:1425 [inline]
 tcp_write_queue_purge include/net/tcp.h:1631 [inline]
 tcp_write_err+0x296/0x630 net/ipv4/tcp_timer.c:39
 tcp_fastopen_synack_timer net/ipv4/tcp_timer.c:384 [inline]
 tcp_retransmit_timer+0x4ca/0x25a0 net/ipv4/tcp_timer.c:421
 tcp_write_timer_handler+0x434/0x780 net/ipv4/tcp_timer.c:583
 tcp_write_timer+0xc8/0x160 net/ipv4/tcp_timer.c:601
 call_timer_fn+0x14a/0x650 kernel/time/timer.c:1280
 expire_timers+0x232/0x4d0 kernel/time/timer.c:1319
 __run_timers kernel/time/timer.c:1644 [inline]
 run_timer_softirq+0x1d5/0x5a0 kernel/time/timer.c:1657
 __do_softirq+0x254/0xa1d kernel/softirq.c:288
 invoke_softirq kernel/softirq.c:368 [inline]
 irq_exit+0x193/0x240 kernel/softirq.c:409
 exiting_irq arch/x86/include/asm/apic.h:648 [inline]
 smp_apic_timer_interrupt+0x141/0x5e0 arch/x86/kernel/apic/apic.c:1102
 apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:793
 </IRQ>
RIP: 0010:preempt_schedule_irq+0xa6/0x140 kernel/sched/core.c:3611
RSP: 0018:ffff888095857990 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10
RAX: 1ffffffff0fa2d23 RBX: dffffc0000000000 RCX: 1ffff1100b0f0d1a
RDX: 0000000000000000 RSI: ffff8880587868b0 RDI: ffff888058786884
RBP: ffffed100b0f0c00 R08: ffff88821fff7058 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888058786000
R13: ffffffff87d16918 R14: 0000000000000000 R15: 0000000000000000
 retint_kernel+0x1b/0x2d
RIP: 0010:lock_acquire+0x1f9/0x3f0 kernel/locking/lockdep.c:4002
RSP: 0018:ffff888095857a68 EFLAGS: 00000296 ORIG_RAX: ffffffffffffff10
RAX: 1ffffffff0fa2d21 RBX: 0000000000000000 RCX: 0000000000007532
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: 0000000000000286
RBP: ffff888058786000 R08: ffffffff8a0b4310 R09: 0000000000040094
R10: ffff8880587868b0 R11: ffff888058786000 R12: 00000000014080c0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000001
 fs_reclaim_acquire mm/page_alloc.c:3557 [inline]
 fs_reclaim_acquire+0xf4/0x120 mm/page_alloc.c:3554
 slab_pre_alloc_hook mm/slab.h:416 [inline]
 slab_alloc mm/slab.c:3376 [inline]
 __do_kmalloc mm/slab.c:3718 [inline]
 __kmalloc+0x4f/0x400 mm/slab.c:3729
 kmalloc_array include/linux/slab.h:607 [inline]
 kcalloc include/linux/slab.h:618 [inline]
 check_cfg+0xbf/0x6b0 kernel/bpf/verifier.c:3614
 bpf_check+0xa9b/0x18a0 kernel/bpf/verifier.c:5041
 bpf_prog_load+0x626/0x1050 kernel/bpf/syscall.c:1057
 SYSC_bpf kernel/bpf/syscall.c:1512 [inline]
 SyS_bpf+0x1336/0x3590 kernel/bpf/syscall.c:1477
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45d5b9
RSP: 002b:00007f64d67c6c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000001c40 RCX: 000000000045d5b9
RDX: 0000000000000048 RSI: 00000000200054c0 RDI: 0000000000000005
RBP: 000000000118cf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffc3f3a11df R14: 00007f64d67c79c0 R15: 000000000118cf4c
INFO: rcu_sched detected stalls on CPUs/tasks:
	1-...: (10501 ticks this GP) idle=f32/140000000000001/0 softirq=18491/18491 fqs=4 
	(detected by 0, t=10561 jiffies, g=1582, c=1581, q=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 10447 Comm: syz-executor.1 Not tainted 4.14.196-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff888058786000 task.stack: ffff888095850000
RIP: 0010:lookup_chain_cache kernel/locking/lockdep.c:2362 [inline]
RIP: 0010:lookup_chain_cache_add kernel/locking/lockdep.c:2381 [inline]
RIP: 0010:validate_chain kernel/locking/lockdep.c:2435 [inline]
RIP: 0010:__lock_acquire+0xa9b/0x3f20 kernel/locking/lockdep.c:3491
RSP: 0018:ffff8880aeb07820 EFLAGS: 00000046
RAX: 1ffffffff136652b RBX: ffffffff89b32940 RCX: 00000000000035fa
RDX: 1ffffffff141292a RSI: 00000000bf5666fb RDI: ffffffff89b32958
RBP: dffffc0000000000 R08: ffffffff8a094950 R09: 00000000000c2001
R10: ffff888058786928 R11: ffff888058786000 R12: ffff888058786940
R13: 0000000000000000 R14: 3650be5b53fd30e9 R15: ffffffff8a5a5c00
FS:  00007f64d67c7700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000016a8660 CR3: 00000000a7336000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x8c/0xc0 kernel/locking/spinlock.c:160
 __debug_check_no_obj_freed lib/debugobjects.c:738 [inline]
 debug_check_no_obj_freed+0x135/0x674 lib/debugobjects.c:776
 free_pages_prepare mm/page_alloc.c:1063 [inline]
 __free_pages_ok+0x215/0xeb0 mm/page_alloc.c:1261
 __put_page+0xb9/0x2f0 mm/swap.c:111
 put_page include/linux/mm.h:875 [inline]
 __skb_frag_unref include/linux/skbuff.h:2801 [inline]
 skb_release_data+0x25a/0x820 net/core/skbuff.c:568
 skb_release_all net/core/skbuff.c:631 [inline]
 __kfree_skb+0x46/0x60 net/core/skbuff.c:645
 sk_wmem_free_skb include/net/sock.h:1425 [inline]
 tcp_write_queue_purge include/net/tcp.h:1631 [inline]
 tcp_write_err+0x296/0x630 net/ipv4/tcp_timer.c:39
 tcp_fastopen_synack_timer net/ipv4/tcp_timer.c:384 [inline]
 tcp_retransmit_timer+0x4ca/0x25a0 net/ipv4/tcp_timer.c:421
 tcp_write_timer_handler+0x434/0x780 net/ipv4/tcp_timer.c:583
 tcp_write_timer+0xc8/0x160 net/ipv4/tcp_timer.c:601
 call_timer_fn+0x14a/0x650 kernel/time/timer.c:1280
 expire_timers+0x232/0x4d0 kernel/time/timer.c:1319
 __run_timers kernel/time/timer.c:1644 [inline]
 run_timer_softirq+0x1d5/0x5a0 kernel/time/timer.c:1657
 __do_softirq+0x254/0xa1d kernel/softirq.c:288
 invoke_softirq kernel/softirq.c:368 [inline]
 irq_exit+0x193/0x240 kernel/softirq.c:409
 exiting_irq arch/x86/include/asm/apic.h:648 [inline]
 smp_apic_timer_interrupt+0x141/0x5e0 arch/x86/kernel/apic/apic.c:1102
 apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:793
 </IRQ>
RIP: 0010:preempt_schedule_irq+0xa6/0x140 kernel/sched/core.c:3611
RSP: 0018:ffff888095857990 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10
RAX: 1ffffffff0fa2d23 RBX: dffffc0000000000 RCX: 1ffff1100b0f0d1a
RDX: 0000000000000000 RSI: ffff8880587868b0 RDI: ffff888058786884
RBP: ffffed100b0f0c00 R08: ffff88821fff7058 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888058786000
R13: ffffffff87d16918 R14: 0000000000000000 R15: 0000000000000000
 retint_kernel+0x1b/0x2d
RIP: 0010:lock_acquire+0x1f9/0x3f0 kernel/locking/lockdep.c:4002
RSP: 0018:ffff888095857a68 EFLAGS: 00000296 ORIG_RAX: ffffffffffffff10
RAX: 1ffffffff0fa2d21 RBX: 0000000000000000 RCX: 0000000000007532
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: 0000000000000286
RBP: ffff888058786000 R08: ffffffff8a0b4310 R09: 0000000000040094
R10: ffff8880587868b0 R11: ffff888058786000 R12: 00000000014080c0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000001
 fs_reclaim_acquire mm/page_alloc.c:3557 [inline]
 fs_reclaim_acquire+0xf4/0x120 mm/page_alloc.c:3554
 slab_pre_alloc_hook mm/slab.h:416 [inline]
 slab_alloc mm/slab.c:3376 [inline]
 __do_kmalloc mm/slab.c:3718 [inline]
 __kmalloc+0x4f/0x400 mm/slab.c:3729
 kmalloc_array include/linux/slab.h:607 [inline]
 kcalloc include/linux/slab.h:618 [inline]
 check_cfg+0xbf/0x6b0 kernel/bpf/verifier.c:3614
 bpf_check+0xa9b/0x18a0 kernel/bpf/verifier.c:5041
 bpf_prog_load+0x626/0x1050 kernel/bpf/syscall.c:1057
 SYSC_bpf kernel/bpf/syscall.c:1512 [inline]
 SyS_bpf+0x1336/0x3590 kernel/bpf/syscall.c:1477
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45d5b9
RSP: 002b:00007f64d67c6c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000001c40 RCX: 000000000045d5b9
RDX: 0000000000000048 RSI: 00000000200054c0 RDI: 0000000000000005
RBP: 000000000118cf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffc3f3a11df R14: 00007f64d67c79c0 R15: 000000000118cf4c
Code: 85 db 74 55 48 83 eb 08 74 4f 48 bd 00 00 00 00 00 fc ff df eb 06 48 83 eb 08 74 3d 48 8d 7b 18 48 89 f8 48 c1 e8 03 80 3c 28 00 <0f> 85 24 1f 00 00 4c 3b 73 18 0f 84 81 fd ff ff 48 8d 7b 08 48

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/09/04 05:45 linux-4.14.y 2f166cdcf8a9 abf9ba4f .config console log report ci2-linux-4-14
2020/06/27 12:59 linux-4.14.y b850307b279c 032b4239 .config console log report ci2-linux-4-14
2020/02/29 10:44 linux-4.14.y 78d697fc93f9 c88c7b75 .config console log report ci2-linux-4-14
2020/01/05 15:59 linux-4.14.y 84f5ad468100 d646e21f .config console log report ci2-linux-4-14
* Struck through repros no longer work on HEAD.