[v5.15] INFO: rcu detected stall in io_sq_thread

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dc027a595035 Linux 5.15.209
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17410f2e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=ed147b9607a8b9f8a408
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/586ac2a2fd9d/disk-dc027a59.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/06dcb6a2fcd3/vmlinux-dc027a59.xz
kernel image: https://storage.googleapis.com/syzbot-assets/567131e0cbcc/bzImage-dc027a59.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ed147b...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P6541/1:b..l
(detected by 0, t=10502 jiffies, g=24169, q=106)
task:syz.0.729 state:R running task stack:26544 pid: 6541 ppid: 4192 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6571
preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6596
preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
__raw_spin_unlock include/linux/spinlock_api_smp.h:152 [inline]
_raw_spin_unlock+0x36/0x40 kernel/locking/spinlock.c:186
spin_unlock include/linux/spinlock.h:404 [inline]
filemap_map_pages+0x1054/0x13b0 mm/filemap.c:3353
do_fault_around mm/memory.c:4243 [inline]
do_read_fault mm/memory.c:4258 [inline]
do_fault mm/memory.c:4392 [inline]
handle_pte_fault mm/memory.c:4650 [inline]
__handle_mm_fault mm/memory.c:4785 [inline]
handle_mm_fault+0x25bc/0x4410 mm/memory.c:4883
faultin_page mm/gup.c:976 [inline]
__get_user_pages+0x94b/0x11e0 mm/gup.c:1197
populate_vma_page_range+0x213/0x290 mm/gup.c:1529
__mm_populate+0x275/0x3b0 mm/gup.c:1638
mm_populate include/linux/mm.h:2646 [inline]
vm_mmap_pgoff+0x212/0x2d0 mm/util.c:556
ksys_mmap_pgoff+0x140/0x790 mm/mmap.c:1635
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f1c4887de59
RSP: 002b:00007f1c46ad7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f1c48af6fa0 RCX: 00007f1c4887de59
RDX: b635773f06ebbeef RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007f1c48913d6f R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1c48af7038 R14: 00007f1c48af6fa0 R15: 00007ffe7f492de8
</TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10523 jiffies! g24169 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: Possible timer handling issue on cpu=1 timer-softirq=9275
rcu: rcu_preempt kthread starved for 10524 jiffies! g24169 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27536 pid: 15 ppid: 2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2117
rcu_gp_fqs_loop+0x2be/0x11d0 kernel/rcu/tree.c:1972
rcu_gp_kthread+0x9b/0x370 kernel/rcu/tree.c:2145
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 6546 Comm: iou-sqp-6539 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:enqueue_hrtimer+0x165/0x370 kernel/time/hrtimer.c:1072
Code: 00 00 44 89 f9 d3 e5 43 80 7c 25 00 00 74 08 4c 89 f7 e8 8e 2d 55 00 4d 8b 3e 49 83 c7 44 4c 89 f8 48 c1 e8 03 42 0f b6 04 20 <84> c0 0f 85 b7 00 00 00 41 09 2f 48 8d 7b 38 48 89 f8 48 c1 e8 03
RSP: 0018:ffffc90000dd0d08 EFLAGS: 00000807
RAX: 0000000000000000 RBX: ffff888078c0fb40 RCX: 0000000000000002
RDX: 0000000000010000 RSI: 0000000000000002 RDI: 0000000000000020
RBP: 0000000000000004 R08: ffffffff8d8a06ef R09: 1ffffffff1b140dd
R10: dffffc0000000000 R11: fffffbfff1b140de R12: dffffc0000000000
R13: 1ffff11017225478 R14: ffff8880b912a3c0 R15: ffff8880b912a284
FS: 00007f5fb00226c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2ee1aff8 CR3: 0000000024641000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
__run_hrtimer kernel/time/hrtimer.c:1702 [inline]
__hrtimer_run_queues+0x5fa/0xb70 kernel/time/hrtimer.c:1749
hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1811
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
__sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:lock_is_held_type+0x13a/0x190 kernel/locking/lockdep.c:5671
Code: 75 40 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 75 46 41 f7 c5 00 02 00 00 74 01 fb 65 48 8b 04 25 28 00 00 00 <48> 3b 44 24 08 75 3c 89 e8 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f
RSP: 0018:ffffc900034a7bb8 EFLAGS: 00000206
RAX: 2afb3fd348ad4200 RBX: ffff88802a019dc0 RCX: 2afb3fd348ad4200
RDX: 0000000000000000 RSI: ffffffff8a2b4420 RDI: ffffffff8a7a09c0
RBP: 0000000000000000 R08: ffff88802a019dc7 R09: 1ffff110054033b8
R10: dffffc0000000000 R11: ffffed10054033b9 R12: 0000000000000001
R13: 0000000000000246 R14: ffffffff8c31f420 R15: ffff88802a01a8d8
lock_is_held include/linux/lockdep.h:287 [inline]
___might_sleep+0xea/0x610 kernel/sched/core.c:9624
io_sq_thread+0xbeb/0x1240 io_uring/io_uring.c:7739
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
vkms_vblank_simulate: vblank timer overrun
vkms_vblank_simulate: vblank timer overrun
vkms_vblank_simulate: vblank timer overrun


---
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 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