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INFO: rcu detected stall in sys_unlinkat

Status: upstream: reported on 2025/10/17 23:40
Reported-by: syzbot+5df22bf0bc5f0deb62f9@syzkaller.appspotmail.com
First crash: 88d, last: 6d08h
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_unlinkat ext4 net 1 4 1006d 1207d 0/29 auto-obsoleted due to no activity on 2023/07/13 16:11
upstream INFO: rcu detected stall in sys_unlinkat (3) tomoyo mm 1 31 197d 222d 0/29 auto-obsoleted due to no activity on 2025/10/09 16:45
upstream INFO: rcu detected stall in sys_unlinkat (2) tomoyo 1 1 871d 871d 0/29 auto-obsoleted due to no activity on 2023/11/25 04:08
linux-5.15 INFO: rcu detected stall in sys_unlinkat 1 1 577d 577d 0/3 auto-obsoleted due to no activity on 2024/09/24 13:32

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 GPs behind) idle=54c4/1/0x4000000000000000 softirq=24019/24022 fqs=2
rcu: 	(detected by 0, t=10505 jiffies, g=25009, q=173 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 5764 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:check_region_inline mm/kasan/generic.c:169 [inline]
RIP: 0010:kasan_check_range+0x12/0x290 mm/kasan/generic.c:187
Code: 0f 0b b8 ea ff ff ff c3 0f 0b b8 ea ff ff ff c3 cc cc cc cc cc cc cc cc 66 0f 1f 00 b0 01 48 85 f6 0f 84 b8 01 00 00 55 41 57 <41> 56 41 55 41 54 53 4c 8d 04 37 49 39 f8 0f 82 5a 02 00 00 49 89
RSP: 0018:ffffc900001f0b48 EFLAGS: 00000002
RAX: 0000000000000001 RBX: 0000000000000001 RCX: ffffffff81677b7b
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8e4a2128
RBP: ffffc900001f0c70 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff5200003e174 R12: ffffffff8175e84d
R13: dffffc0000000000 R14: ffffffff97115558 R15: 1ffff9200003e178
FS:  000055556dd59500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055556dd7c608 CR3: 0000000061d0c000 CR4: 00000000003526e0
Call Trace:
 <IRQ>
 instrument_atomic_read include/linux/instrumented.h:68 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 cpumask_test_cpu include/linux/cpumask.h:504 [inline]
 cpu_online include/linux/cpumask.h:1082 [inline]
 trace_lock_release include/trace/events/lock.h:69 [inline]
 lock_release+0xab/0x8b0 kernel/locking/lockdep.c:5765
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:149 [inline]
 _raw_spin_unlock_irqrestore+0x71/0x110 kernel/locking/spinlock.c:194
 debug_hrtimer_deactivate kernel/time/hrtimer.c:455 [inline]
 debug_deactivate+0x1d/0x1d0 kernel/time/hrtimer.c:511
 __run_hrtimer kernel/time/hrtimer.c:1718 [inline]
 __hrtimer_run_queues+0x2bf/0xc40 kernel/time/hrtimer.c:1814
 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1876
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
 __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0x9f/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:__sanitizer_cov_trace_cmp8+0x7e/0x80 kernel/kcov.c:294
Code: c1 e1 05 4c 8d 51 28 4d 39 ca 77 1e 49 ff c0 4c 89 02 48 c7 44 0a 08 06 00 00 00 48 89 7c 0a 10 48 89 74 0a 18 48 89 44 0a 20 <c3> 90 f3 0f 1e fa 48 8b 04 24 65 48 8b 15 60 22 7e 7e 65 8b 0d 61
RSP: 0018:ffffc900042ff748 EFLAGS: 00000293
RAX: ffffffff813aa506 RBX: ffffffff81000000 RCX: ffff888020fcbc00
RDX: 0000000000000000 RSI: ffffffff81000000 RDI: ffffffff813ad461
RBP: ffffc900042ff8d8 R08: ffffc900042ff801 R09: 0000000000000000
R10: ffffc900042ff888 R11: fffff5200085ff1d R12: ffffc900042ff888
R13: dffffc0000000000 R14: ffffc900042ff8bd R15: ffffffff813ad461
 orc_find arch/x86/kernel/unwind_orc.c:206 [inline]
 unwind_next_frame+0x1c6/0x2970 arch/x86/kernel/unwind_orc.c:494
 __unwind_start+0x66a/0x7e0 arch/x86/kernel/unwind_orc.c:760
 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
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 __call_rcu_common kernel/rcu/tree.c:2721 [inline]
 call_rcu+0x158/0x930 kernel/rcu/tree.c:2837
 __dentry_kill+0x4ef/0x650 fs/dcache.c:625
 dentry_kill+0xb8/0x290 fs/dcache.c:-1
 dput+0xfe/0x1e0 fs/dcache.c:918
 do_rmdir+0x2a9/0x5c0 fs/namei.c:4265
 __do_sys_unlinkat fs/namei.c:4441 [inline]
 __se_sys_unlinkat fs/namei.c:4435 [inline]
 __x64_sys_unlinkat+0xc4/0xe0 fs/namei.c:4435
 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: 0033:0x7fd903b8ed27
Code: 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 07 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff46eeaad8 EFLAGS: 00000207 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 0000000000000065 RCX: 00007fd903b8ed27
RDX: 0000000000000200 RSI: 00007fff46eebc20 RDI: 00000000ffffff9c
RBP: 00007fd903c13d7d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000100 R11: 0000000000000207 R12: 00007fff46eebc20
R13: 00007fd903c13d7d R14: 0000000000033779 R15: 00007fff46eebc60
 </TASK>
rcu: rcu_preempt kthread starved for 10495 jiffies! g25009 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:27304 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:2168
 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: 41 Comm: kworker/u4:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:csd_lock_wait kernel/smp.c:311 [inline]
RIP: 0010:smp_call_function_many_cond+0xddf/0x1130 kernel/smp.c:855
Code: 45 8b 2c 24 44 89 ee 83 e6 01 31 ff e8 6a d7 0a 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 a5 d3 0a 00 eb 38 f3 90 <42> 0f b6 04 2b 84 c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 89 d3
RSP: 0018:ffffc90000b1f780 EFLAGS: 00000293
RAX: ffffffff817abd37 RBX: 1ffff110171e826d RCX: ffff888018af8000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90000b1f900 R08: ffffffff90d94507 R09: 1ffffffff21b28a0
R10: dffffc0000000000 R11: fffffbfff21b28a1 R12: ffff8880b8f41368
R13: dffffc0000000000 R14: ffff8880b8e3d148 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbf045f3f98 CR3: 000000000cb30000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1022
 on_each_cpu include/linux/smp.h:71 [inline]
 text_poke_sync arch/x86/kernel/alternative.c:2222 [inline]
 text_poke_bp_batch+0x318/0x930 arch/x86/kernel/alternative.c:2432
 text_poke_flush arch/x86/kernel/alternative.c:2623 [inline]
 text_poke_finish+0x30/0x50 arch/x86/kernel/alternative.c:2630
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 static_key_enable_cpuslocked+0x123/0x240 kernel/jump_label.c:207
 static_key_enable+0x1a/0x20 kernel/jump_label.c:220
 toggle_allocation_gate+0xaa/0x250 mm/kfence/core.c:831
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 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>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/08 09:37 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_unlinkat
2025/10/17 23:40 linux-6.6.y 0bbbd97a442d 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_unlinkat
* Struck through repros no longer work on HEAD.