[v6.6] INFO: rcu detected stall in sys_unlinkat

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0bbbd97a442d Linux 6.6.112
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=151d7dcd980000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=5df22bf0bc5f0deb62f9
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7e387d57d751/disk-0bbbd97a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/810d42505365/vmlinux-0bbbd97a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5d2fe115c227/bzImage-0bbbd97a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5df22b...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-...!: (1 GPs behind) idle=3c4c/1/0x4000000000000000 softirq=81288/81289 fqs=1
rcu: (detected by 1, t=10506 jiffies, g=104093, q=114 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 17181 Comm: syz.4.3882 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:arch_atomic_set arch/x86/include/asm/atomic.h:28 [inline]
RIP: 0010:raw_atomic_set include/linux/atomic/atomic-arch-fallback.h:490 [inline]
RIP: 0010:atomic_set include/linux/atomic/atomic-instrumented.h:68 [inline]
RIP: 0010:taprio_set_budgets+0x240/0x390 net/sched/sch_taprio.c:688
Code: e8 75 19 e8 f8 49 83 fc 10 77 69 e8 2a 15 e8 f8 49 8d ac 1f 80 00 00 00 48 89 ef be 04 00 00 00 e8 f5 6f 3f f9 48 8b 44 24 28 <48> 8d 3c 18 48 89 f8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f
RSP: 0018:ffffc90000007c00 EFLAGS: 00000056
RAX: ffff88802eadd080 RBX: 0000000000000000 RCX: ffffffff889d75bb
RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffff88802eadd080
RBP: ffff88802eadd080 R08: ffff88802eadd083 R09: 1ffff11005d5ba10
R10: dffffc0000000000 R11: ffffed1005d5ba11 R12: 0000000000000000
R13: 0000000000000000 R14: ffff888078eb42e0 R15: ffff88802eadd000
FS: 00007fb343b636c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b33a23ffc CR3: 000000006b990000 CR4: 00000000003506f0
Call Trace:
<IRQ>
advance_sched+0x964/0xc80 net/sched/sch_taprio.c:993
__run_hrtimer kernel/time/hrtimer.c:1750 [inline]
__hrtimer_run_queues+0x51e/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:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xa9/0x110 kernel/locking/spinlock.c:194
Code: 74 05 e8 ba cc 13 f7 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 92 4b e3 f6 65 8b 05 73 96 8b 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc9000c107140 EFLAGS: 00000206
RAX: 5ed7c2c743a71a00 RBX: 0000000000000a06 RCX: 5ed7c2c743a71a00
RDX: dffffc0000000000 RSI: ffffffff8aaabce0 RDI: 0000000000000001
RBP: ffffc9000c1071c8 R08: ffffffff90da76a7 R09: 1ffffffff21b4ed4
R10: dffffc0000000000 R11: fffffbfff21b4ed5 R12: dffffc0000000000
R13: ffff88807600c000 R14: ffff888017840a80 R15: 1ffff92001820e28
spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
get_partial_node+0x4ff/0x540 mm/slub.c:2338
get_partial mm/slub.c:2416 [inline]
___slab_alloc+0x9cd/0x1300 mm/slub.c:3230
__slab_alloc mm/slub.c:3339 [inline]
__slab_alloc_node mm/slub.c:3392 [inline]
slab_alloc_node mm/slub.c:3485 [inline]
__kmem_cache_alloc_node+0x1a2/0x260 mm/slub.c:3534
__do_kmalloc_node mm/slab_common.c:1006 [inline]
__kmalloc+0xa4/0x240 mm/slab_common.c:1020
kmalloc include/linux/slab.h:604 [inline]
get_mem_for_virtual_node fs/reiserfs/fix_node.c:2286 [inline]
fix_nodes+0x6034/0x82e0 fs/reiserfs/fix_node.c:2626
reiserfs_cut_from_item+0x309/0x1f10 fs/reiserfs/stree.c:1740
reiserfs_rmdir+0x3bc/0x730 fs/reiserfs/namei.c:957
vfs_rmdir+0x370/0x4d0 fs/namei.c:4196
do_rmdir+0x29e/0x5c0 fs/namei.c:4255
__do_sys_unlinkat fs/namei.c:4433 [inline]
__se_sys_unlinkat fs/namei.c:4427 [inline]
__x64_sys_unlinkat+0xc4/0xe0 fs/namei.c:4427
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: 0033:0x7fb342d8efc9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb343b63038 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 00007fb342fe5fa0 RCX: 00007fb342d8efc9
RDX: 0000000000000200 RSI: 0000200000000000 RDI: ffffffffffffff9c
RBP: 00007fb342e11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb342fe6038 R14: 00007fb342fe5fa0 R15: 00007ffd9b3be3d8
</TASK>
rcu: rcu_preempt kthread starved for 10500 jiffies! g104093 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:26728 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:2167
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: 1 PID: 2976 Comm: kworker/u4:8 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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 da d6 0a 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 15 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 f9 d2
RSP: 0000:ffffc9000ba67780 EFLAGS: 00000293
RAX: ffffffff817ab7d7 RBX: 1ffff110171c8791 RCX: ffff88802b9b8000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000ba67900 R08: ffffffff90da7507 R09: 1ffffffff21b4ea0
R10: dffffc0000000000 R11: fffffbfff21b4ea1 R12: ffff8880b8e43c88
R13: dffffc0000000000 R14: ffff8880b8f3d348 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6079238000 CR3: 000000000cb30000 CR4: 00000000003506e0
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>


---
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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7c87defbd336 Linux 6.1.169
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=162082ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=0f1b146d0ffd354871a8
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=179e92ce580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cf55a056d548/disk-7c87defb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/af13139876bb/vmlinux-7c87defb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/02c231cd5348/Image-7c87defb.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+0f1b14...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:

rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P3935/1:b..l
(detected by 1, t=10502 jiffies, g=3457, q=405 ncpus=2)
task:udevd state:R running task stack:0 pid:3935 ppid:1 flags:0x00000004
Call trace:
__switch_to+0x2f4/0x550 arch/arm64/kernel/process.c:555
context_switch kernel/sched/core.c:5245 [inline]
__schedule+0xdd0/0x1b0c kernel/sched/core.c:6562
preempt_schedule_irq+0x8c/0x1ac kernel/sched/core.c:6874
arm64_preempt_schedule_irq+0x44/0x54 arch/arm64/kernel/entry-common.c:265
__el1_irq arch/arm64/kernel/entry-common.c:474 [inline]
el1_interrupt+0x3c/0x54 arch/arm64/kernel/entry-common.c:486
el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:491
el1h_64_irq+0x64/0x68 arch/arm64/kernel/entry.S:581
arch_local_irq_restore arch/arm64/include/asm/irqflags.h:122 [inline]
lock_acquire+0x24c/0x63c kernel/locking/lockdep.c:5665
rcu_lock_acquire+0x44/0x54 include/linux/rcupdate.h:350
rcu_read_lock include/linux/rcupdate.h:791 [inline]
page_ext_get+0x2c/0x2c4 mm/page_ext.c:157
__page_table_check_zero+0xf4/0x2b0 mm/page_table_check.c:146
page_table_check_free include/linux/page_table_check.h:46 [inline]
free_pages_prepare mm/page_alloc.c:1487 [inline]
free_pcp_prepare mm/page_alloc.c:1536 [inline]
free_unref_page_prepare+0x9e4/0xaf0 mm/page_alloc.c:3413
free_unref_page+0x7c/0x3a0 mm/page_alloc.c:3508
free_the_page mm/page_alloc.c:781 [inline]
__free_pages+0x1a0/0x1cc mm/page_alloc.c:5746
__free_slab+0x104/0x294 mm/slub.c:2021
free_slab mm/slub.c:2036 [inline]
discard_slab+0x58/0xd4 mm/slub.c:2042
__unfreeze_partials+0x150/0x190 mm/slub.c:2591
put_cpu_partial+0x18c/0x1f8 mm/slub.c:2667
__slab_free+0x1a4/0x268 mm/slub.c:3564
do_slab_free mm/slub.c:3641 [inline]
___cache_free+0x168/0x198 mm/slub.c:3694
qlink_free+0x5c/0xa0 mm/kasan/quarantine.c:168
qlist_free_all+0x3c/0xcc mm/kasan/quarantine.c:187
kasan_quarantine_reduce+0x124/0x130 mm/kasan/quarantine.c:294
__kasan_slab_alloc+0x2c/0x88 mm/kasan/common.c:306
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook+0x74/0x430 mm/slab.h:737
slab_alloc_node mm/slub.c:3359 [inline]
slab_alloc mm/slub.c:3367 [inline]
__kmem_cache_alloc_lru mm/slub.c:3374 [inline]
kmem_cache_alloc+0x22c/0x308 mm/slub.c:3383
getname_flags+0xb8/0x45c fs/namei.c:139
getname fs/namei.c:218 [inline]
__do_sys_unlinkat fs/namei.c:-1 [inline]
__se_sys_unlinkat fs/namei.c:4434 [inline]
__arm64_sys_unlinkat+0xb4/0xfc fs/namei.c:4434
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g3457 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: Possible timer handling issue on cpu=0 timer-softirq=1166
rcu: rcu_preempt kthread starved for 10502 jiffies! g3457 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:0 pid:16 ppid:2 flags:0x00000008
Call trace:
__switch_to+0x2f4/0x550 arch/arm64/kernel/process.c:555
context_switch kernel/sched/core.c:5245 [inline]
__schedule+0xdd0/0x1b0c kernel/sched/core.c:6562
schedule+0xc4/0x170 kernel/sched/core.c:6638
schedule_timeout+0x194/0x2f4 kernel/time/timer.c:2168
rcu_gp_fqs_loop+0x2b4/0x1378 kernel/rcu/tree.c:1706
rcu_gp_kthread+0xb4/0x2fc kernel/rcu/tree.c:1905
kthread+0x250/0x2d8 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

rcu: Stack dump where RCU GP kthread last ran:

Task dump for CPU 0:
task:syz.1.23 state:R running task stack:0 pid:4504 ppid:4439 flags:0x00000000
Call trace:
__switch_to+0x2f4/0x550 arch/arm64/kernel/process.c:555
0xffff800008000000

---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.