[syzbot] [fs?] [usb?] [input?] INFO: rcu detected stall in __fsnotify_parent (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6916d5703ddf Merge tag 'drm-fixes-2026-05-16' of https://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13437cc8580000
kernel config: https://syzkaller.appspot.com/x/.config?x=59da38148f3a3d24
dashboard link: https://syzkaller.appspot.com/bug?extid=27ce6cc06c1311c152f5
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=123e8596580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/637181391a5c/disk-6916d570.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bfbefc8a3671/vmlinux-6916d570.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a419831b32a6/bzImage-6916d570.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+27ce6c...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P4963/1:b..l

rcu: (detected by 1, t=10506 jiffies, g=15565, q=1900 ncpus=2)
task:acpid state:R
running task stack:22856 pid:4963 tgid:4963 ppid:1 task_flags:0x400040 flags:0x00080001
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5388 [inline]
__schedule+0x1295/0x67a0 kernel/sched/core.c:7189
preempt_schedule_irq+0x50/0x90 kernel/sched/core.c:7513
irqentry_exit_to_kernel_mode_preempt include/linux/irq-entry-common.h:476 [inline]
irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:547 [inline]
irqentry_exit+0x205/0x7e0 kernel/entry/common.c:164
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lock_acquire+0x5e/0x370 kernel/locking/lockdep.c:5872
Code: 05 3b a2 26 12 83 f8 07 0f 87 d9 02 00 00 48 0f a3 05 46 41 f3 0e 0f 82 a4 02 00 00 8b 35 ce 74 f3 0e 85 f6 0f 85 bf 00 00 00 <48> 8b 44 24 30 65 48 2b 05 dd a1 26 12 0f 85 ed 02 00 00 48 83 c4
RSP: 0018:ffffc9000342fb30 EFLAGS: 00000206

RAX: 0000000000000046 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8defcf06 RDI: ffffffff8c1c3a00
RBP: ffffffff8e7e57a0 R08: 0000000086db7919 R09: 0000000000000007
R10: 0000000000000200 R11: 0000000000000000 R12: 0000000000000002
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
rcu_read_lock include/linux/rcupdate.h:838 [inline]
dput.part.0+0x4c/0x570 fs/dcache.c:971
dput+0x1f/0x30 fs/dcache.c:968
__fsnotify_parent+0x694/0xca0 fs/notify/fsnotify.c:242
fsnotify_parent include/linux/fsnotify.h:96 [inline]
fsnotify_path include/linux/fsnotify.h:113 [inline]
fsnotify_file include/linux/fsnotify.h:127 [inline]
fsnotify_file include/linux/fsnotify.h:116 [inline]
fsnotify_access include/linux/fsnotify.h:425 [inline]
vfs_read+0x486/0xb30 fs/read_write.c:578
ksys_read+0x1f8/0x250 fs/read_write.c:717
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7feac7fb3407
RSP: 002b:00007ffc6dd51e00 EFLAGS: 00000202
ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007feac7f29780 RCX: 00007feac7fb3407
RDX: 0000000000000018 RSI: 00007ffc6dd51e50 RDI: 000000000000000b
RBP: 00007ffc6dd51e50 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000556e2f8031e4
R13: 0000556e4a9f2380 R14: 0000000000000007 R15: 000000000000000b
</TASK>
rcu: rcu_preempt kthread starved for 4298 jiffies! g15565 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:27992 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5388 [inline]
__schedule+0x1295/0x67a0 kernel/sched/core.c:7189
__schedule_loop kernel/sched/core.c:7268 [inline]
schedule+0xdd/0x390 kernel/sched/core.c:7283
schedule_timeout+0x127/0x280 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x1a9/0x900 kernel/rcu/tree.c:2095
rcu_gp_kthread+0x179/0x230 kernel/rcu/tree.c:2297
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 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:
CPU: 1 UID: 0 PID: 5978 Comm: syz.1.18 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:write_comp_data+0x40/0x90 kernel/kcov.c:246
Code: 02 12 a9 00 01 ff 00 74 1b f6 c4 01 74 07 a9 00 00 ff 00 74 05 c3 cc cc cc cc 8b 87 d4 16 00 00 85 c0 74 f1 8b 87 b0 16 00 00 <83> f8 03 75 e6 48 8b 87 b8 16 00 00 8b bf b4 16 00 00 48 8b 30 48
RSP: 0018:ffffc900024af648 EFLAGS: 00000246

RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81fc2bcd
RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff88805a5e0000
RBP: ffff8880b8443320 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000003
R13: ffffed1017088665 R14: 0000000000000001 R15: ffff8880b853c5c0
FS: 0000000000000000(0000) GS:ffff88812446d000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8c6e1b56e8 CR3: 0000000059a89000 CR4: 00000000003526f0
Call Trace:
<TASK>
csd_lock_wait kernel/smp.c:342 [inline]
smp_call_function_many_cond+0x5ad/0x1700 kernel/smp.c:892
on_each_cpu_cond_mask+0x40/0x90 kernel/smp.c:1057
__flush_tlb_multi arch/x86/include/asm/paravirt.h:46 [inline]
flush_tlb_multi arch/x86/mm/tlb.c:1361 [inline]
flush_tlb_mm_range+0x45f/0x16f0 arch/x86/mm/tlb.c:1451
tlb_flush arch/x86/include/asm/tlb.h:23 [inline]
tlb_flush_mmu_tlbonly include/asm-generic/tlb.h:509 [inline]
tlb_flush_mmu_tlbonly include/asm-generic/tlb.h:499 [inline]
tlb_flush_mmu mm/mmu_gather.c:423 [inline]
tlb_finish_mmu+0x3fe/0x810 mm/mmu_gather.c:549
exit_mmap+0x454/0xa10 mm/mmap.c:1313
__mmput+0x12a/0x410 kernel/fork.c:1178
mmput+0x67/0x80 kernel/fork.c:1201
exit_mm kernel/exit.c:582 [inline]
do_exit+0x8b2/0x2af0 kernel/exit.c:964
do_group_exit+0xd5/0x2a0 kernel/exit.c:1119
get_signal+0x20ff/0x2210 kernel/signal.c:3037
arch_do_signal_or_restart+0x91/0x7e0 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
exit_to_user_mode_loop+0x8b/0x4f0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
do_syscall_64+0x706/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7a9eb5d68e
Code: Unable to access opcode bytes at 0x7f7a9eb5d664.
RSP: 002b:00007fffdcda5708 EFLAGS: 00000246
ORIG_RAX: 00000000000000e6
RAX: 0000000000000000 RBX: 000055558fc36500 RCX: 00007f7a9eb5d68e
RDX: 00007fffdcda5760 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fffdcda58b0
R13: 00007f7a9ee15fac R14: 000000000002bbe6 R15: 00007f7a9ee15fa0
</TASK>


---
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.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup