syzbot

 sign-in | mailing list | source | docs
🐞 Open [1436]
≡ Subsystems
🐞 Fixed [6971]
🐞 Invalid [18179]
⬇ Missing Backports [223]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
Total Repo Heatmap Subsystems Heatmap
✨ AI
💬 Send us feedback

INFO: rcu detected stall in kcompactd (3)

Status: auto-obsoleted due to no activity on 2026/03/05 20:24
Subsystems: mm
[Documentation on labels]
First crash: 126d, last: 94d
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in kcompactd mm 1 1 940d 940d 0/29 auto-obsoleted due to no activity on 2023/11/10 08:17
linux-6.1 INFO: rcu detected stall in kcompactd 1 1 636d 636d 0/3 auto-obsoleted due to no activity on 2024/09/19 19:09
upstream INFO: rcu detected stall in kcompactd (2) mm 1 C error unreliable 6 466d 646d 0/29 auto-obsoleted due to no activity on 2025/03/08 05:35
upstream BUG: soft lockup in kcompactd kvm 1 1 1588d 1584d 0/29 auto-closed as invalid on 2022/01/31 12:36

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P7352/1:b..l P34/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=113881, q=380 ncpus=2)
task:kcompactd0      state:R  running task     stack:27192 pid:34    tgid:34    ppid:2      task_flags:0x210040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7256
 irqentry_exit+0x36/0x90 kernel/entry/common.c:211
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lock_acquire+0x62/0x350 kernel/locking/lockdep.c:5872
Code: 94 08 12 83 f8 07 0f 87 bc 02 00 00 89 c0 48 0f a3 05 12 18 e9 0e 0f 82 74 02 00 00 8b 35 8a 48 e9 0e 85 f6 0f 85 8d 00 00 00 <48> 8b 44 24 30 65 48 2b 05 29 94 08 12 0f 85 c7 02 00 00 48 83 c4
RSP: 0018:ffffc90000aa6f50 EFLAGS: 00000206
RAX: 0000000000000046 RBX: ffffffff8e3c4720 RCX: 00000000ed4415e6
RDX: 0000000000000000 RSI: ffffffff8da056e0 RDI: ffffffff8bf07040
RBP: 0000000000000002 R08: 913ec92e81bc4d99 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:867 [inline]
 ___pte_offset_map+0x44/0x4f0 mm/pgtable-generic.c:286
 __pte_offset_map include/linux/mm.h:3118 [inline]
 pte_offset_map_rw_nolock+0x37/0x1a0 mm/pgtable-generic.c:326
 map_pte mm/page_vma_mapped.c:37 [inline]
 page_vma_mapped_walk+0xae8/0x2f20 mm/page_vma_mapped.c:291
 try_to_migrate_one+0x442/0x35b0 mm/rmap.c:2339
 __rmap_walk_file+0x359/0x620 mm/rmap.c:2918
 rmap_walk_file+0x174/0x1f0 mm/rmap.c:2951
 rmap_walk mm/rmap.c:2962 [inline]
 try_to_migrate+0x200/0x300 mm/rmap.c:2634
 migrate_folio_unmap mm/migrate.c:1319 [inline]
 migrate_pages_batch+0x98a/0x3bb0 mm/migrate.c:1882
 migrate_pages_sync+0x12d/0x8a0 mm/migrate.c:1999
 migrate_pages+0x1b5f/0x23a0 mm/migrate.c:2108
 compact_zone+0x2018/0x4750 mm/compaction.c:2647
 kcompactd_do_work+0x4a3/0xa50 mm/compaction.c:3098
 kcompactd+0x406/0xeb0 mm/compaction.c:3192
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
task:kworker/1:9     state:R  running task     stack:21912 pid:7352  tgid:7352  ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: events_power_efficient gc_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7256
 irqentry_exit+0x36/0x90 kernel/entry/common.c:211
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:__seqprop_spinlock_sequence include/linux/seqlock.h:227 [inline]
RIP: 0010:nf_conntrack_get_ht include/net/netfilter/nf_conntrack.h:342 [inline]
RIP: 0010:gc_worker+0x2d5/0x16e0 net/netfilter/nf_conntrack_core.c:1548
Code: 00 00 48 c7 c7 68 b0 82 90 e8 57 7b 19 f8 9c 5b 81 e3 00 02 00 00 31 ff 48 89 de e8 95 9f 3d f8 58 48 85 db 0f 85 d4 0f 00 00 <e8> 16 a4 3d f8 8b 1d d0 46 03 07 41 89 dc 31 ff 41 83 e4 01 44 89
RSP: 0018:ffffc9000c127b48 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff897f74c9
RDX: ffff8880236e2480 RSI: ffffffff897f74d8 RDI: 0000000000000007
RBP: ffffffff9af8d3ac R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff88814cc00000
R13: 0000000000040000 R14: dffffc0000000000 R15: 000000000000176b
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
 process_scheduled_works kernel/workqueue.c:3346 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 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 9080 jiffies! g113881 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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:27784 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 __schedule_loop kernel/sched/core.c:7011 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:7026
 schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1ea/0xaf0 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x26d/0x380 kernel/rcu/tree.c:2285
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 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:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:82
Code: e7 6c 02 c3 cc cc cc cc 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 03 a6 29 00 fb f4 <e9> 3c 0a 03 00 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
RSP: 0000:ffffc90000197de8 EFLAGS: 000002c6
RAX: 0000000008ae8525 RBX: 0000000000000001 RCX: ffffffff8b6082a9
RDX: 0000000000000000 RSI: ffffffff8da2b0a2 RDI: ffffffff8bf07040
RBP: ffffed1003b53490 R08: 0000000000000001 R09: ffffed10170a6655
R10: ffff8880b85332ab R11: 0000000000000001 R12: 0000000000000001
R13: ffff88801da9a480 R14: ffffffff908203d0 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888124b08000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd0df6a7407 CR3: 000000007522d000 CR4: 00000000003526f0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000083
DR3: ffffffffefffff15 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:767
 default_idle_call+0x6c/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:190 [inline]
 do_idle+0x38d/0x500 kernel/sched/idle.c:330
 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:428
 start_secondary+0x21d/0x2b0 arch/x86/kernel/smpboot.c:315
 common_startup_64+0x13e/0x148
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/03 03:59 upstream 6146a0f1dfae 2c50b6a9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in kcompactd
2025/12/05 20:18 linux-next 6987d58a9cbc d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in kcompactd
* Struck through repros no longer work on HEAD.