INFO: rcu detected stall in sys_mkdir (2)

Status: upstream: reported C repro on 2025/12/22 06:04
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+8469452c867bc303645b@syzkaller.appspotmail.com
First crash: 216d, last: 32d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/01/07 linux-6.1.y (ToT) 50cbba13faa2 C [report] INFO: rcu detected stall in corrupted
2025/12/24 upstream (ToT) b927546677c8 C Didn't crash
▶ ▼ Similar bugs (17)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in sys_mkdir 1 1 576d 576d 0/3 auto-obsoleted due to no activity on 2025/04/06 10:37
linux-6.6 INFO: rcu detected stall in sys_mkdir (3) 1 1 24d 24d 0/2 upstream: reported on 2026/07/02 03:34
linux-6.1 INFO: rcu detected stall in sys_mkdir 1 1 509d 509d 0/3 auto-obsoleted due to no activity on 2025/06/11 20:27
upstream INFO: rcu detected stall in sys_mkdir (3) cgroups 1 1 2391d 2391d 0/29 closed as invalid on 2020/01/08 05:33
linux-5.15 INFO: rcu detected stall in sys_mkdir (3) 1 1 140d 140d 0/3 auto-obsoleted due to no activity on 2026/06/16 08:45
upstream INFO: rcu detected stall in sys_mkdir (7) ext4 1 1 1066d 1066d 0/29 auto-obsoleted due to no activity on 2023/10/24 07:40
linux-5.15 INFO: rcu detected stall in sys_mkdir (2) 1 1 310d 310d 0/3 auto-obsoleted due to no activity on 2025/12/28 08:27
linux-6.6 INFO: rcu detected stall in sys_mkdir 1 1 341d 341d 0/2 auto-obsoleted due to no activity on 2025/11/27 00:13
upstream INFO: rcu detected stall in sys_mkdir mm 1 2 2559d 2561d 0/29 auto-closed as invalid on 2019/10/25 14:21
upstream INFO: rcu detected stall in sys_mkdir (2) cgroups 1 5 2426d 2427d 0/29 closed as invalid on 2019/12/04 14:04
upstream INFO: rcu detected stall in sys_mkdir (6) ext4 1 2 1637d 1646d 0/29 closed as invalid on 2022/02/08 09:50
upstream INFO: rcu detected stall in sys_mkdir (4) mm 1 2 2391d 2391d 0/29 closed as invalid on 2020/01/09 08:13
upstream INFO: rcu detected stall in sys_mkdir (9) prio:high mm 1 syz done error 6 68d 547d 0/29 upstream: reported syz repro on 2025/01/25 04:35
upstream INFO: rcu detected stall in sys_mkdir (8) fs 1 1 665d 665d 0/29 auto-obsoleted due to no activity on 2024/12/28 09:04
upstream INFO: rcu detected stall in sys_mkdir (5) tomoyo 1 1 1773d 1773d 0/29 auto-closed as invalid on 2021/12/15 23:48
linux-6.6 INFO: rcu detected stall in sys_mkdir (2) 1 1 233d 233d 0/2 auto-obsoleted due to no activity on 2026/03/14 17:07
android-5-15 BUG: soft lockup in sys_mkdir 1 2 799d 804d 0/2 auto-obsoleted due to no activity on 2024/08/15 15:43
▶ ▼ Fix bisection attempts (4)
Created Duration User Patch Repo Result
2026/03/25 01:28 1m fix candidate upstream error job log
2026/02/22 19:29 4m fix candidate upstream error job log
2026/01/23 03:32 1m fix candidate upstream error job log
2026/01/21 23:17 0m bisect fix linux-6.1.y error job log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4268/1:b..l
	(detected by 1, t=10503 jiffies, g=5749, q=25 ncpus=2)
task:syz-executor351 state:R  running task     stack:26240 pid:4268  ppid:4263   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6873
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:preempt_count_sub+0x61/0x160 kernel/sched/core.c:5749
Code: ff ff ff 7f 39 cf 7f 25 81 ff ff 00 00 00 0f 93 c1 84 c0 0f 95 c0 08 c8 74 53 65 8b 05 40 ad aa 7e f7 df 65 01 3d 37 ad aa 7e <5b> 5d c3 e8 d7 40 ac 02 85 c0 74 f4 48 c7 c0 e8 42 ff 8d 48 c1 e8
RSP: 0018:ffffc90003cc7a70 EFLAGS: 00000297
RAX: 0000000080000001 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 00000000ffffffff
RBP: 0000000000000001 R08: dffffc0000000000 R09: ffffed100eb0fc42
R10: ffffed100eb0fc42 R11: 1ffff1100eb0fc41 R12: 1ffff1100eb0fc49
R13: 0000000000000000 R14: ffff88807587e248 R15: dffffc0000000000
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x24/0x40 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 lockref_get_not_dead+0x72/0xb0 lib/lockref.c:190
 __legitimize_path fs/namei.c:708 [inline]
 legitimize_path fs/namei.c:718 [inline]
 try_to_unlazy+0x125/0x5a0 fs/namei.c:779
 complete_walk+0x113/0x350 fs/namei.c:888
 path_parentat fs/namei.c:2536 [inline]
 __filename_parentat+0x221/0x610 fs/namei.c:2558
 filename_parentat fs/namei.c:2576 [inline]
 filename_create+0xcc/0x450 fs/namei.c:3865
 do_mkdirat+0x9d/0x430 fs/namei.c:4129
 __do_sys_mkdir fs/namei.c:4159 [inline]
 __se_sys_mkdir fs/namei.c:4157 [inline]
 __x64_sys_mkdir+0x6a/0x80 fs/namei.c:4157
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f04215e2e97
RSP: 002b:00007ffea8dd6b28 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 00007f042163b0ae RCX: 00007f04215e2e97
RDX: 00007f042163b101 RSI: 00000000000001c0 RDI: 00007f042163b106
RBP: 00007f042163b0e6 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f042164133c
R13: 00007f042163b106 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10533 jiffies! g5749 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:28192 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x95/0x380 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </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: 4293 Comm: syz-executor351 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:__kasan_check_read+0x0/0x10 mm/kasan/shadow.c:31
Code: 41 5c 41 5d 41 5e 41 5f 5d c3 48 c7 c7 fa c5 39 8c eb 0a 48 c7 c7 ec 2d 23 8c 48 89 de e8 68 53 34 08 31 ed eb d7 00 00 cc cc <89> f6 48 8b 0c 24 31 d2 e9 a3 ec ff ff 0f 1f 00 89 f6 48 8b 0c 24
RSP: 0018:ffffc90003e374f8 EFLAGS: 00000002
RAX: 0000000000000008 RBX: 0000000000000048 RCX: ffffffff81630c92
RDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffffffff908c8248
RBP: ffffc90003e37750 R08: dffffc0000000000 R09: fffffbfff211904a
R10: fffffbfff211904a R11: 1ffffffff2119049 R12: ffff888079783b80
R13: 0000000000000008 R14: 0000000000000000 R15: ffff8880797846d0
FS:  0000555580f67480(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000006b000 CR3: 00000000299eb000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 instrument_atomic_read include/linux/instrumented.h:72 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 hlock_class kernel/locking/lockdep.c:228 [inline]
 check_wait_context kernel/locking/lockdep.c:4724 [inline]
 __lock_acquire+0x5e3/0x7c50 kernel/locking/lockdep.c:4999
 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
 seqcount_lockdep_reader_access+0xc6/0x1c0 include/linux/seqlock.h:102
 timekeeping_get_delta kernel/time/timekeeping.c:254 [inline]
 timekeeping_get_ns kernel/time/timekeeping.c:388 [inline]
 ktime_get+0x7b/0x270 kernel/time/timekeeping.c:848
 clockevents_program_min_delta+0x55/0x340 kernel/time/clockevents.c:241
 hrtimer_start_range_ns+0xb9a/0xfc0 kernel/time/hrtimer.c:1349
 posixtimer_rearm+0x131/0x340 kernel/time/posix-timers.c:329
 dequeue_signal+0x1b6/0x4b0 kernel/signal.c:704
 get_signal+0x547/0x1350 kernel/signal.c:2751
 arch_do_signal_or_restart+0xb7/0x1240 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f04215e4119
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffea8dd6958 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00007f04215e4119
RDX: 000020000006b000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00007f042164133c R09: 00007f042164133c
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f042164133c
R13: 00007f042163b106 R14: 00007ffea8dd69a0 R15: 0000000000000000
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/22 06:04 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_mkdir
2026/06/24 04:36 linux-6.1.y fdb6fcb41cc7 042555ff .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in sys_mkdir
* Struck through repros no longer work on HEAD.