syzbot

 sign-in | mailing list | source | docs
🐞 Open [455]
🐞 Fixed [23]
🐞 Invalid [238]
⬇ Missing Backports [16]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
💬 Send us feedback

INFO: rcu detected stall in kthreadd

Status: auto-obsoleted due to no activity on 2025/12/02 17:39
Reported-by: syzbot+a441f65b16acc820fa61@syzkaller.appspotmail.com
First crash: 260d, last: 260d
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in kthreadd 1 1 727d 727d 0/3 auto-obsoleted due to no activity on 2024/08/23 07:20
upstream INFO: rcu detected stall in kthreadd (2) mm 1 C unreliable error 116 6h36m 559d 0/29 upstream: reported C repro on 2024/10/30 03:07
linux-6.6 INFO: rcu detected stall in kthreadd (2) 1 2 29d 104d 0/2 upstream: reported on 2026/01/27 21:22
upstream INFO: rcu detected stall in kthreadd mm 1 2 746d 758d 0/29 auto-obsoleted due to no activity on 2024/07/25 04:06
android-5-15 BUG: soft lockup in kthreadd (2) 1 1 502d 502d 0/2 auto-obsoleted due to no activity on 2025/03/25 17:14
android-5-15 BUG: soft lockup in kthreadd origin:lts 1 C 2 652d 673d 0/2 auto-obsoleted due to no activity on 2024/11/05 13:04

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P2/1:b..l P5453/1:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=61261, q=164 ncpus=2)
task:dhcpcd          state:R  running task     stack:23760 pid:5453  ppid:1      flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6866
 preempt_schedule+0xab/0xc0 kernel/sched/core.c:6890
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0xfa/0x110 kernel/locking/spinlock.c:194
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 __wake_up_common_lock kernel/sched/wait.c:140 [inline]
 __wake_up_sync_key+0x11f/0x190 kernel/sched/wait.c:213
 sock_def_readable+0x1e1/0x430 net/core/sock.c:3329
 unix_dgram_sendmsg+0x10cc/0x1720 net/unix/af_unix.c:2141
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 sock_write_iter+0x2bb/0x3f0 net/socket.c:1160
 do_iter_readv_writev fs/read_write.c:-1 [inline]
 do_iter_write+0x79a/0xc70 fs/read_write.c:860
 vfs_writev fs/read_write.c:933 [inline]
 do_writev+0x252/0x410 fs/read_write.c:976
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f4bfc36e407
RSP: 002b:00007fff43a9b450 EFLAGS: 00000202 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f4bfc2e4740 RCX: 00007f4bfc36e407
RDX: 0000000000000005 RSI: 00007fff43a9b4b0 RDI: 000000000000000a
RBP: 000056063b551c90 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000056063b551c90
R13: 000000000000012c R14: 00000000ffffffff R15: 0000000000000000
 </TASK>
task:kthreadd        state:R  running task     stack:25928 pid:2     ppid:0      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7009
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:__sanitizer_cov_trace_pc+0x5c/0x60 kernel/kcov.c:234
Code: 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 08 <c3> 0f 1f 00 f3 0f 1e fa 48 8b 04 24 65 48 8b 15 70 2e 7e 7e 65 8b
RSP: 0018:ffffc90000077300 EFLAGS: 00000293
RAX: ffffffff812ebc2f RBX: ffffc900000773a8 RCX: ffff88801a271e00
RDX: 0000000000000000 RSI: ffff88801a271e00 RDI: ffffc90000077340
RBP: dffffc0000000000 R08: ffffc90000077407 R09: 0000000000000000
R10: ffffc900000773a8 R11: fffff5200000ee81 R12: ffffc90000077340
R13: ffffc900000773c8 R14: ffffc900000773c8 R15: ffff88801a271e00
 get_stack_info+0x1f/0x170 arch/x86/kernel/dumpstack_64.c:193
 __unwind_start+0x48b/0x7e0 arch/x86/kernel/unwind_orc.c:729
 unwind_start arch/x86/include/asm/unwind.h:64 [inline]
 arch_stack_walk+0xf8/0x190 arch/x86/kernel/stacktrace.c:24
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 save_stack+0xf7/0x1f0 mm/page_owner.c:128
 __reset_page_owner+0x4e/0x190 mm/page_owner.c:149
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
 __slab_free+0x35e/0x410 mm/slub.c:3722
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 ____kasan_kmalloc mm/kasan/common.c:340 [inline]
 __kasan_kmalloc+0x22/0xa0 mm/kasan/common.c:383
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc+0xb4/0x240 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 lsm_cred_alloc security/security.c:577 [inline]
 security_prepare_creds+0x4b/0x130 security/security.c:2968
 prepare_creds+0x427/0x5d0 kernel/cred.c:237
 copy_creds+0x105/0xa70 kernel/cred.c:308
 copy_process+0x92a/0x3d70 kernel/fork.c:2365
 kernel_clone+0x21b/0x840 kernel/fork.c:2914
 kernel_thread+0x10d/0x160 kernel/fork.c:2976
 create_kthread kernel/kthread.c:411 [inline]
 kthreadd+0x560/0x730 kernel/kthread.c:766
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: rcu_preempt kthread starved for 9566 jiffies! g61261 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:27752 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.6.102-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:__orc_find arch/x86/kernel/unwind_orc.c:-1 [inline]
RIP: 0010:orc_find arch/x86/kernel/unwind_orc.c:227 [inline]
RIP: 0010:unwind_next_frame+0x46d/0x2970 arch/x86/kernel/unwind_orc.c:494
Code: 4e 8d 24 ad c4 f2 56 8e 44 29 ed 49 8d 5c ac fc 49 39 dc 76 0d e8 03 e4 4a 00 4d 29 e4 e9 a4 00 00 00 4c 89 e5 4c 89 64 24 28 <48> ba 00 00 00 00 00 fc ff df 4c 8b 74 24 48 48 89 d8 4c 29 e0 48
RSP: 0018:ffffc90000006258 EFLAGS: 00000283
RAX: ffffffff813aa572 RBX: ffffffff8ec5f308 RCX: 0000000000000100
RDX: ffffffff8ca93380 RSI: 00000000001bbff1 RDI: 00000000001bc012
RBP: ffffffff8ec5f288 R08: ffffc900000063f0 R09: 0000000000000021
R10: 0000000000000004 R11: 0000000000000100 R12: ffffffff8ec5f288
R13: 00000000001bbff1 R14: ffffc9000000635d R15: 0000000000098014
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000277030 CR3: 00000000311c8000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1806 [inline]
 slab_free_freelist_hook+0x130/0x1b0 mm/slub.c:1832
 slab_free mm/slub.c:3816 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3829
 skb_kfree_head net/core/skbuff.c:945 [inline]
 skb_free_head net/core/skbuff.c:957 [inline]
 skb_release_data+0x634/0x800 net/core/skbuff.c:987
 skb_release_all net/core/skbuff.c:1053 [inline]
 __kfree_skb net/core/skbuff.c:1067 [inline]
 kfree_skb_reason+0x10e/0x170 net/core/skbuff.c:1103
 enqueue_to_backlog+0x1d2/0xe30 net/core/dev.c:4870
 netif_rx_internal+0x119/0x4e0 net/core/dev.c:5126
 __netif_rx+0x78/0xc0 net/core/dev.c:5146
 loopback_xmit+0x457/0x6c0 drivers/net/loopback.c:89
 __netdev_start_xmit include/linux/netdevice.h:4943 [inline]
 netdev_start_xmit include/linux/netdevice.h:4957 [inline]
 xmit_one net/core/dev.c:3607 [inline]
 dev_hard_start_xmit+0x246/0x740 net/core/dev.c:3623
 sch_direct_xmit+0x252/0x4a0 net/sched/sch_generic.c:342
 qdisc_restart net/sched/sch_generic.c:407 [inline]
 __qdisc_run+0xab2/0x1570 net/sched/sch_generic.c:415
 __dev_xmit_skb net/core/dev.c:3907 [inline]
 __dev_queue_xmit+0xf02/0x35a0 net/core/dev.c:4379
 dev_queue_xmit include/linux/netdevice.h:3113 [inline]
 neigh_hh_output include/net/neighbour.h:526 [inline]
 neigh_output include/net/neighbour.h:540 [inline]
 ip6_finish_output2+0xdf5/0x1650 net/ipv6/ip6_output.c:141
 synproxy_send_tcp_ipv6+0x4bc/0x670 net/netfilter/nf_synproxy_core.c:851
 synproxy_send_client_synack_ipv6+0x7e8/0xc60 net/netfilter/nf_synproxy_core.c:897
 nft_synproxy_eval_v6+0x36f/0x560 net/netfilter/nft_synproxy.c:90
 nft_synproxy_do_eval+0x3d4/0x570 net/netfilter/nft_synproxy.c:145
 expr_call_ops_eval net/netfilter/nf_tables_core.c:240 [inline]
 nft_do_chain+0x3f9/0x1580 net/netfilter/nf_tables_core.c:288
 nft_do_chain_inet+0x25b/0x330 net/netfilter/nft_chain_filter.c:161
 nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
 nf_hook_slow+0xbd/0x200 net/netfilter/core.c:626
 nf_hook include/linux/netfilter.h:259 [inline]
 NF_HOOK+0x204/0x390 include/linux/netfilter.h:302
 NF_HOOK+0x303/0x390 include/linux/netfilter.h:304
 __netif_receive_skb_one_core net/core/dev.c:5596 [inline]
 __netif_receive_skb+0xcc/0x290 net/core/dev.c:5710
 process_backlog+0x380/0x6e0 net/core/dev.c:6038
 __napi_poll+0xc0/0x460 net/core/dev.c:6600
 napi_poll net/core/dev.c:6667 [inline]
 net_rx_action+0x5ea/0xbf0 net/core/dev.c:6803
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xc7/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:148
Code: cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d e3 e6 3a 00 f3 0f 1e fa fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc 66 0f 1f 00 55 41 57 41 56
RSP: 0018:ffffffff8ca07d80 EFLAGS: 000002c6
RAX: 4d681a84c4d30400 RBX: ffffffff8161914b RCX: 4d681a84c4d30400
RDX: 0000000000000001 RSI: ffffffff8aaab9c0 RDI: ffffffff8afc66c0
RBP: ffffffff8ca07eb8 R08: ffff8880b8e36d4b R09: 1ffff110171c6da9
R10: dffffc0000000000 R11: ffffed10171c6daa R12: ffffffff8e4a8828
R13: 0000000000000000 R14: 0000000000000000 R15: 1ffffffff1952670
 arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:753
 default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
 cpuidle_idle_call kernel/sched/idle.c:170 [inline]
 do_idle+0x1eb/0x510 kernel/sched/idle.c:282
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:380
 rest_init+0x2e2/0x300 init/main.c:732
 arch_call_rest_init+0xe/0x10 init/main.c:829
 start_kernel+0x459/0x4e0 init/main.c:1074
 x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:555
 x86_64_start_kernel+0x60/0x60 arch/x86/kernel/head64.c:536
 secondary_startup_64_no_verify+0x179/0x17b
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/24 17:38 linux-6.6.y bb9c90ab9c5a bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in kthreadd
* Struck through repros no longer work on HEAD.