INFO: rcu detected stall in sys_exit_group

Status: upstream: reported C repro on 2025/07/21 16:02
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+48904dad9520cbb5ce21@syzkaller.appspotmail.com
First crash: 448d, last: 2d09h
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/01/06 upstream (ToT) 7f98ab9da046 C [report] INFO: rcu detected stall in do_idle
2026/09/25 upstream (ToT) [unknown] C Failed due to an error; will retry later
▶ ▼ Similar bugs (17)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_exit_group (7) net 1 syz, C unreliable inconclusive 91 44d 1823d 0/29 upstream: reported C repro on 2021/10/15 18:41
upstream INFO: rcu detected stall in sys_exit_group (6) mm 1 syz, C 4 2203d 2209d 19/29 fixed on 2021/03/10 01:48
linux-5.15 INFO: rcu detected stall in sys_exit_group (2) 1 3 907d 942d 0/3 auto-obsoleted due to no activity on 2024/07/27 04:53
linux-6.1 INFO: rcu detected stall in sys_exit_group (3) origin:upstream 1 syz, C error 36 3d01h 993d 0/3 upstream: reported C repro on 2024/01/23 11:05
linux-6.1 INFO: rcu detected stall in sys_exit_group (2) 1 1 1140d 1140d 0/3 auto-obsoleted due to no activity on 2023/12/07 20:57
linux-6.1 INFO: rcu detected stall in sys_exit_group 1 1 1251d 1251d 0/3 auto-obsoleted due to no activity on 2023/08/23 09:06
linux-5.15 INFO: rcu detected stall in sys_exit_group 1 1 1202d 1202d 0/3 auto-obsoleted due to no activity on 2023/10/06 21:30
upstream INFO: rcu detected stall in sys_exit_group (2) mm cgroups 1 56 2504d 2506d 0/29 closed as invalid on 2019/12/04 14:14
upstream INFO: rcu detected stall in sys_exit_group (3) mm 1 8 2469d 2470d 0/29 closed as invalid on 2020/01/08 05:23
upstream INFO: rcu detected stall in sys_exit_group (4) mm 1 13 2469d 2469d 0/29 closed as invalid on 2020/01/09 08:13
upstream INFO: rcu detected stall in sys_exit_group (5) mm 1 1 2390d 2390d 0/29 auto-closed as invalid on 2020/06/25 07:58
linux-5.15 INFO: rcu detected stall in sys_exit_group (3) 1 2 697d 730d 0/3 auto-obsoleted due to no activity on 2025/02/22 19:05
linux-5.15 INFO: rcu detected stall in sys_exit_group (4) origin:upstream 1 syz, C error 12 16d 389d 0/3 upstream: reported C repro on 2025/09/19 02:54
upstream INFO: rcu detected stall in sys_exit_group kernel 1 syz, C done 1 2585d 2581d 13/29 fixed on 2019/10/09 10:54
android-5-10 BUG: soft lockup in sys_exit_group 1 1 813d 813d 0/2 auto-obsoleted due to no activity on 2024/10/19 10:22
android-5-10 BUG: soft lockup in sys_exit_group (2) 1 1 256d 256d 0/2 auto-obsoleted due to no activity on 2026/04/29 20:43
android-5-15 BUG: soft lockup in sys_exit_group 1 syz, C error 7 775d 918d 0/2 auto-obsoleted due to no activity on 2024/12/07 01:30

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P56/1:b..l P5786/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=9329, q=62 ncpus=2)
task:udevd           state:R  running task     stack:26696 pid:5786  ppid:5139   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7011
 irqentry_exit+0x67/0x70 kernel/entry/common.c:441
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:__sanitizer_cov_trace_const_cmp8+0x0/0x80 kernel/kcov.c:317
Code: c0 4c 89 01 48 c7 44 11 08 05 00 00 00 48 89 7c 11 10 48 89 74 11 18 48 89 44 11 20 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 <f3> 0f 1e fa 48 8b 04 24 65 48 8b 0d 00 23 7c 7e 65 8b 15 01 23 7c
RSP: 0018:ffffc90004527540 EFLAGS: 00000246
RAX: ffffffff81cf7204 RBX: ffffc90004527600 RCX: ffff88803087bc00
RDX: 0000000000000000 RSI: ffffffff81cf7204 RDI: 0000000000000000
RBP: ffffc900045275d0 R08: ffff88803087bc00 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000000 R12: ffffffff81cf7204
R13: 1ffff1100610f82f R14: ffffffff81762b60 R15: ffffc90004527548
 arch_stack_walk+0x12a/0x190 arch/x86/kernel/stacktrace.c:27
 stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
 save_stack+0x125/0x230 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:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2505
 release_pages+0x208a/0x2300 mm/swap.c:1022
 tlb_batch_pages_flush mm/mmu_gather.c:99 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:294 [inline]
 tlb_flush_mmu+0x379/0x510 mm/mmu_gather.c:301
 tlb_finish_mmu+0xf4/0x220 mm/mmu_gather.c:425
 exit_mmap+0x428/0xb90 mm/mmap.c:3315
 __mmput+0x118/0x3a0 kernel/fork.c:1362
 exit_mm+0x23f/0x340 kernel/exit.c:576
 do_exit+0x909/0x2530 kernel/exit.c:877
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1032
 __do_sys_exit_group kernel/exit.c:1043 [inline]
 __se_sys_exit_group kernel/exit.c:1041 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1041
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f4507af16c5
RSP: 002b:00007fffb931b678 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000564b4402c8a0 RCX: 00007f4507af16c5
RDX: 00000000000000e7 RSI: fffffffffffffe68 RDI: 0000000000000000
RBP: 0000564b44022910 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fffb931b6c0 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
task:kworker/0:2     state:R  running task     stack:24240 pid:56    ppid:2      flags:0x00004000
Workqueue: events_power_efficient gc_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7011
 irqentry_exit+0x67/0x70 kernel/entry/common.c:441
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
RIP: 0010:rcu_read_lock include/linux/rcupdate.h:786 [inline]
RIP: 0010:gc_worker+0x284/0x14a0 net/netfilter/nf_conntrack_core.c:1459
Code: e8 71 cf a8 f8 48 8d 05 00 00 00 00 48 c7 c7 e0 20 f3 8d 31 f6 31 d2 b9 02 00 00 00 45 31 c0 45 31 c9 48 89 84 24 90 00 00 00 <50> e8 86 48 9f f8 48 83 c4 08 e8 ed c0 c9 01 89 c3 31 ff 89 c6 e8
RSP: 0018:ffffc9000131fa60 EFLAGS: 00000246
RAX: ffffffff88c95066 RBX: 0000000000006c00 RCX: 0000000000000002
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8df320e0
RBP: ffffc9000131fbb0 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1ed8b5e R12: 000000000000d80f
R13: dffffc0000000000 R14: 0000000000040000 R15: 0000000000006c08
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 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: rcu_preempt kthread starved for 10572 jiffies! g9329 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:26856 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x30d/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 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:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:pv_native_safe_halt+0xf/0x10 arch/x86/kernel/paravirt.c:148
Code: 99 17 02 c3 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 13 39 35 00 fb f4 <c3> 66 0f 1f 00 55 41 57 41 56 41 54 53 50 8b 2f eb 2c 89 cb 80 f9
RSP: 0018:ffffffff8dc07d80 EFLAGS: 000002c6
RAX: a7e97f98b132b300 RBX: ffffffff81631e31 RCX: a7e97f98b132b300
RDX: 0000000000000001 RSI: ffffffff8acacfe0 RDI: ffffffff8b1d5160
RBP: ffffffff8dc07eb8 R08: ffff8880b8c36b6b R09: 1ffff11017186d6d
R10: dffffc0000000000 R11: ffffed1017186d6e R12: 1ffffffff1b80fbc
R13: dffffc0000000000 R14: 1ffffffff1b92688 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b8c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000380 CR3: 000000002bfdc000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 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:178 [inline]
 do_idle+0x221/0x5c0 kernel/sched/idle.c:302
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:401
 rest_init+0x2e2/0x300 init/main.c:705
 arch_call_rest_init+0xe/0x10 init/main.c:801
 start_kernel+0x461/0x4e0 init/main.c:1046
 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 (18):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/10 18:59 linux-6.6.y a91a6aa9253c 4f92358f .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2026/01/06 18:28 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2026/01/06 07:52 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2026/01/05 22:52 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2026/09/08 19:49 linux-6.6.y 8b73de7da85f 243b72f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2026/07/04 01:50 linux-6.6.y d1cfde2d5d15 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2026/06/03 21:24 linux-6.6.y 924b4a879cbb 234057e5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2026/05/14 20:52 linux-6.6.y 3b9f64db0496 6ccb967e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_exit_group
2026/05/10 14:39 linux-6.6.y 3b9f64db0496 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_exit_group
2026/03/06 11:53 linux-6.6.y 4fc00fe35d46 31e9c887 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2026/02/05 07:34 linux-6.6.y 2cf6f68313dc ea10c935 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2025/12/23 05:35 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2025/11/24 22:31 linux-6.6.y 1e89a1be4fe9 bf6fe8fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2025/09/27 04:24 linux-6.6.y 147338df3487 001c9061 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2025/09/17 02:00 linux-6.6.y 60a9e718726f e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2025/09/03 17:05 linux-6.6.y cc1a1c5b404a 96a211bc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2025/07/22 10:50 linux-6.6.y d96eb99e2f0e 1555463b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
2025/07/21 16:01 linux-6.6.y d96eb99e2f0e 56d87229 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_exit_group
* Struck through repros no longer work on HEAD.