INFO: rcu detected stall in khugepaged (3)

Status: upstream: reported on 2026/08/05 00:01
Subsystems: mm
Labels: prio:normal
[Documentation on labels]
Reported-by: syzbot+d2401aeb74cc84adba04@syzkaller.appspotmail.com
First crash: 544d, last: 20h31m
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
4f1a87d0 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ INFO: rcu detected stall in khugepaged (3) 2026/05/23 06:14 2026/05/23 06:14 2026/05/23 07:17 c69befb3
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [mm?] INFO: rcu detected stall in khugepaged (3) 6 (7) 2026/08/06 17:19
Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in khugepaged (2) mm 1 1 725d 725d 0/29 auto-obsoleted due to no activity on 2024/11/17 09:26
upstream INFO: rcu detected stall in khugepaged mm 1 1 1434d 1434d 0/29 auto-obsoleted due to no activity on 2022/12/08 19:48
linux-6.6 INFO: rcu detected stall in khugepaged 1 1 59d 59d 0/2 upstream: reported on 2026/06/16 00:14

Sample crash report:
bridge0: received packet on veth0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P37/1:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=132713, q=3530 ncpus=2)
task:khugepaged      state:R  running task     stack:26936 pid:37    tgid:37    ppid:2      task_flags:0x200040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x17d9/0x56c0 kernel/sched/core.c:7234
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7556
 irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
 irqentry_exit+0x14f/0x8f0 kernel/entry/common.c:167
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:collapse_huge_page mm/khugepaged.c:1387 [inline]
RIP: 0010:mthp_collapse mm/khugepaged.c:1523 [inline]
RIP: 0010:collapse_scan_pmd mm/khugepaged.c:1785 [inline]
RIP: 0010:collapse_single_pmd+0x2d84/0x3da0 mm/khugepaged.c:2798
Code: 8b 4c 24 30 4c 8b 44 24 28 4c 8d 8c 24 10 02 00 00 e8 a0 9d 00 00 89 c3 48 8b bc 24 50 02 00 00 e8 81 b9 98 09 bf 01 00 00 00 <89> de e8 55 50 8c ff 83 fb 01 0f 85 4c 0b 00 00 83 7c 24 28 09 0f
RSP: 0018:ffffc90000ad7800 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000001
RBP: ffffc90000ad7b50 R08: ffff88807eef3de3 R09: 1ffff1100fdde7bc
R10: dffffc0000000000 R11: ffffed100fdde7bd R12: ffff88807eef3d20
R13: ffff88808609c000 R14: ffff888057a28cc0 R15: 1ffff1100af45217
 collapse_scan_mm_slot mm/khugepaged.c:2913 [inline]
 khugepaged_do_scan mm/khugepaged.c:2993 [inline]
 khugepaged+0xa00/0x1780 mm/khugepaged.c:3048
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: rcu_preempt kthread starved for 318 jiffies! g132713 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:27496 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x17d9/0x56c0 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7326
 schedule_timeout+0x152/0x2c0 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x30c/0x11f0 kernel/rcu/tree.c:2123
 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2325
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 7158 Comm: kworker/u8:9 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: wg-kex-wg1 wg_packet_handshake_send_worker
RIP: 0010:lock_acquire+0x221/0x350 kernel/locking/lockdep.c:5872
Code: ff ff ff e8 51 fd 2d 0a f7 44 24 08 00 02 00 00 0f 84 3a ff ff ff 65 48 8b 05 db f7 c9 11 48 3b 44 24 58 75 33 fb 48 83 c4 60 <5b> 41 5c 41 5d 41 5e 41 5f 5d e9 80 00 31 0a cc 48 8d 3d e8 1e b8
RSP: 0018:ffffc90000006128 EFLAGS: 00000286
RAX: 25e2d8aad197fa00 RBX: 0000000000000000 RCX: 0000000080000303
RDX: 00000000dbb1dfa1 RSI: ffffffff8e4adf3a RDI: ffffffff8c4bbf80
RBP: ffffffff8177827f R08: ffffffff8177827f R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8eb59c60 R12: 0000000000000002
R13: ffffffff8eb59c60 R14: 0000000000000000 R15: 0000000000000246
FS:  0000000000000000(0000) GS:ffff888124f55000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000174030 CR3: 000000004684a000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000400
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 rcu_read_lock include/linux/rcupdate.h:840 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1183 [inline]
 unwind_next_frame+0xac/0x2550 arch/x86/kernel/unwind_orc.c:495
 __unwind_start+0x514/0x660 arch/x86/kernel/unwind_orc.c:787
 unwind_start arch/x86/include/asm/unwind.h:64 [inline]
 arch_stack_walk+0xe3/0x150 arch/x86/kernel/stacktrace.c:24
 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2677 [inline]
 slab_free mm/slub.c:6377 [inline]
 kmem_cache_free+0x182/0x650 mm/slub.c:6504
 skb_ext_reset include/linux/skbuff.h:5117 [inline]
 skb_release_head_state+0x270/0x360 net/core/skbuff.c:1189
 skb_release_all net/core/skbuff.c:1195 [inline]
 __kfree_skb+0x24/0x210 net/core/skbuff.c:1211
 kfree_skb_reason include/linux/skbuff.h:1323 [inline]
 nsim_start_xmit+0x31c/0xd60 drivers/net/netdevsim/netdev.c:181
 __netdev_start_xmit include/linux/netdevice.h:5397 [inline]
 netdev_start_xmit include/linux/netdevice.h:5406 [inline]
 xmit_one net/core/dev.c:3889 [inline]
 dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:3905
 sch_direct_xmit+0x257/0x4c0 net/sched/sch_generic.c:372
 __dev_xmit_skb net/core/dev.c:4214 [inline]
 __dev_queue_xmit+0x177f/0x3820 net/core/dev.c:4836
 dev_queue_xmit include/linux/netdevice.h:3448 [inline]
 br_dev_queue_push_xmit+0x370/0x4b0 net/bridge/br_forward.c:53
 NF_HOOK+0x64e/0x6e0 include/linux/netfilter.h:318
 br_nf_post_routing+0xa53/0xee0 net/bridge/br_netfilter_hooks.c:964
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:619
 nf_hook include/linux/netfilter.h:273 [inline]
 NF_HOOK+0x23e/0x3f0 include/linux/netfilter.h:316
 br_forward_finish+0xd3/0x130 net/bridge/br_forward.c:66
 br_nf_hook_thresh net/bridge/br_netfilter_hooks.c:1165 [inline]
 br_nf_forward_finish+0xa76/0xea0 net/bridge/br_netfilter_hooks.c:667
 NF_HOOK+0x64e/0x6e0 include/linux/netfilter.h:318
 br_nf_forward_ip+0x7eb/0xa30 net/bridge/br_netfilter_hooks.c:721
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:619
 nf_hook include/linux/netfilter.h:273 [inline]
 NF_HOOK+0x23e/0x3f0 include/linux/netfilter.h:316
 __br_forward+0x397/0x540 net/bridge/br_forward.c:115
 br_handle_frame_finish+0x1175/0x1990 net/bridge/br_input.c:229
 br_nf_hook_thresh+0x3dd/0x4c0 net/bridge/br_netfilter_hooks.c:-1
 br_nf_pre_routing_finish_ipv6+0x90c/0xc40 net/bridge/br_netfilter_ipv6.c:-1
 NF_HOOK include/linux/netfilter.h:318 [inline]
 br_nf_pre_routing_ipv6+0x382/0x6f0 net/bridge/br_netfilter_ipv6.c:183
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:291 [inline]
 br_handle_frame+0x127f/0x1510 net/bridge/br_input.c:442
 __netif_receive_skb_core+0x989/0x30b0 net/core/dev.c:6099
 __netif_receive_skb_one_core net/core/dev.c:6210 [inline]
 __netif_receive_skb net/core/dev.c:6325 [inline]
 process_backlog+0x706/0x1860 net/core/dev.c:6676
 __napi_poll+0xaa/0x330 net/core/dev.c:7735
 napi_poll net/core/dev.c:7798 [inline]
 net_rx_action+0x61d/0xf50 net/core/dev.c:7955
 handle_softirqs+0x225/0x840 kernel/softirq.c:622
 do_softirq+0x76/0xd0 kernel/softirq.c:523
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0xf8/0x130 kernel/softirq.c:450
 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:36 [inline]
 wg_packet_handshake_send_worker+0x1b2/0x370 drivers/net/wireguard/send.c:51
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
bridge0: received packet on veth1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)

Crashes (34):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/13 21:32 upstream 3d6d817622b0 a9ede23c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in khugepaged
2026/08/06 10:46 upstream 0d8395707651 cc56899a .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2026/08/05 03:36 upstream c21bb4193868 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in khugepaged
2026/07/31 07:15 upstream 3708dd948844 aaffb173 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in khugepaged
2026/07/01 01:03 upstream dc59e4fea9d8 00e8b0fd .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in khugepaged
2026/06/16 19:43 upstream 6b5a2b7d9bc1 0e4b3e40 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in khugepaged
2026/05/06 23:08 upstream adc1e5c6203c cbcd9ea0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in khugepaged
2026/04/12 08:32 upstream e753c16cb3dd 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in khugepaged
2026/04/01 02:57 upstream d0c3bcd5b897 ef441708 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2026/02/15 02:26 upstream 3e48a11675c5 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2026/01/27 08:57 upstream fcb70a56f4d8 43e1df1d .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2026/01/17 00:39 upstream 39d3389331ab d1b870e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2026/01/13 01:22 upstream 0f61b1860cc3 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in khugepaged
2026/01/03 07:29 upstream 9b0436804460 d1b870e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2026/01/01 16:07 upstream b69053dd3ffb d1b870e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2025/12/25 07:08 upstream ccd1cdca5cd4 d1b870e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2025/12/07 11:06 upstream cc3ee4ba57b7 d1b870e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2025/12/07 10:16 upstream cc3ee4ba57b7 d1b870e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2025/12/04 09:43 upstream 8f7aa3d3c732 d1b870e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2025/12/03 21:34 upstream 3f9f0252130e d1b870e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2025/11/27 01:23 upstream 30f09200cc4a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in khugepaged
2025/11/06 03:28 upstream dc77806cf3b4 a6c9c731 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2025/11/02 09:02 upstream 691d401c7e0e 2c50b6a9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in khugepaged
2025/10/08 04:10 upstream 971199ad2a0f 7e2882b3 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2025/08/04 20:27 upstream d2eedaa3909b f5bcc8dc .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2025/07/02 10:45 upstream 66701750d556 bc80e4f0 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2025/06/22 02:10 upstream 3f75bfff44be d6cdfb8a .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2025/06/10 15:57 upstream f09079bd04a9 5d7e17ca .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in khugepaged
2025/05/11 05:42 upstream 345030986df8 77908e5f .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in khugepaged
2025/05/07 13:12 upstream 0d8d44db295c 350f4ffc .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in khugepaged
2025/02/15 23:27 upstream 7ff71e6d9239 40a34ec9 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in khugepaged
2026/08/06 05:57 upstream 0d8395707651 cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: rcu detected stall in khugepaged
2026/04/21 20:46 upstream 4ee64205ffaa 0b6ab7ec .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: rcu detected stall in khugepaged
2025/07/06 10:54 linux-next 26ffb3d6f02c 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce INFO: rcu detected stall in khugepaged
* Struck through repros no longer work on HEAD.