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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 68efe5a6c16a Linux 5.15.197
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14660074580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e6ed99963d6ee1d
dashboard link: https://syzkaller.appspot.com/bug?extid=dd49d0815935ecc7713e
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/900f9b9bd850/disk-68efe5a6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1e089a5019a6/vmlinux-68efe5a6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b319f477b907/bzImage-68efe5a6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dd49d0...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 1-...!: (1 GPs behind) idle=f1d/1/0x4000000000000000 softirq=29625/29628 fqs=79
(t=10502 jiffies g=45709 q=25549)
rcu: rcu_preempt kthread timer wakeup didn't happen for 8773 jiffies! g45709 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: Possible timer handling issue on cpu=0 timer-softirq=21014
rcu: rcu_preempt kthread starved for 8776 jiffies! g45709 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:27296 pid: 15 ppid: 2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
rcu_gp_kthread+0x98/0x350 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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 9894 Comm: syz.4.1378 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:csd_lock_wait kernel/smp.c:440 [inline]
RIP: 0010:smp_call_function_many_cond+0xb88/0xd70 kernel/smp.c:969
Code: b6 44 05 00 84 c0 0f 85 9d 00 00 00 41 8b 1c 24 89 de 83 e6 01 31 ff e8 66 49 0b 00 83 e3 01 75 07 e8 fc 45 0b 00 eb 43 f3 90 <48> b8 00 00 00 00 00 fc ff df 41 0f b6 44 05 00 84 c0 75 11 41 f7
RSP: 0000:ffffc90004abe7a0 EFLAGS: 00000293
RAX: ffffffff816c863b RBX: 0000000000000001 RCX: ffff88807cff9dc0
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90004abe8e0 R08: dffffc0000000000 R09: fffffbfff1ff541f
R10: fffffbfff1ff541f R11: 1ffffffff1ff541e R12: ffff8880b91405c8
R13: 1ffff110172280b9 R14: ffff8880b903b3c0 R15: 0000000000000001
FS: 000055558d623500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7fe270f4d6 CR3: 0000000044d4c000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
on_each_cpu_cond_mask+0x3b/0x80 kernel/smp.c:1134
__flush_tlb_multi arch/x86/include/asm/paravirt.h:87 [inline]
flush_tlb_multi arch/x86/mm/tlb.c:946 [inline]
arch_tlbbatch_flush+0x22d/0x420 arch/x86/mm/tlb.c:1259
try_to_unmap_flush+0x4c/0xc0 mm/rmap.c:613
shrink_page_list+0x5ec9/0x6b60 mm/vmscan.c:1817
shrink_inactive_list mm/vmscan.c:2223 [inline]
shrink_list mm/vmscan.c:2450 [inline]
shrink_lruvec+0x1170/0x24a0 mm/vmscan.c:2769
shrink_node_memcgs mm/vmscan.c:2956 [inline]
shrink_node+0x10a7/0x2610 mm/vmscan.c:3079
shrink_zones mm/vmscan.c:3285 [inline]
do_try_to_free_pages+0x5da/0x15c0 mm/vmscan.c:3340
try_to_free_mem_cgroup_pages+0x2f6/0x780 mm/vmscan.c:3654
try_charge_memcg+0x3de/0x14a0 mm/memcontrol.c:2654
try_charge mm/memcontrol.c:2779 [inline]
charge_memcg+0x100/0x2e0 mm/memcontrol.c:6765
mem_cgroup_swapin_charge_page+0x1fe/0x310 mm/memcontrol.c:6836
__read_swap_cache_async+0x663/0xa70 mm/swap_state.c:491
read_swap_cache_async mm/swap_state.c:525 [inline]
swap_cluster_readahead+0x6a2/0x7c0 mm/swap_state.c:661
swapin_readahead+0xf3/0xaa0 mm/swap_state.c:854
do_swap_page+0x4b6/0x1f40 mm/memory.c:3622
handle_pte_fault mm/memory.c:4654 [inline]
__handle_mm_fault mm/memory.c:4785 [inline]
handle_mm_fault+0x1ad7/0x43b0 mm/memory.c:4883
do_user_addr_fault+0x489/0xc80 arch/x86/mm/fault.c:1357
handle_page_fault arch/x86/mm/fault.c:1445 [inline]
exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1501
asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0033:0x7f7fe238c750
Code: 74 28 48 85 c9 74 29 45 38 1c 10 75 23 83 c0 01 44 39 d0 75 dc 48 89 f0 25 ff 1f 00 00 49 89 34 c1 41 88 3c 00 31 c0 c3 66 90 <41> 38 3c 10 74 0b 41 88 3c 10 31 c0 49 89 34 d1 c3 b8 01 00 00 00
RSP: 002b:00007ffe0b97a468 EFLAGS: 00010246
RAX: 0000000087d684d6 RBX: 00007f7fe3254720 RCX: ffffffff87d684d6
RDX: 00000000000004d6 RSI: ffffffff87d684d6 RDI: 0000000000000008
RBP: ffffffff87d684d6 R08: 00007f7fe270f000 R09: 00007f7fe2711000
R10: 0000000087d684da R11: 0000000000000008 R12: 0000000000000008
R13: 0000000000000000 R14: ffffffff87d68644 R15: 0000000000007774
</TASK>
NMI backtrace for cpu 1
CPU: 1 PID: 9925 Comm: syz.4.1378 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<IRQ>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
rcu_dump_cpu_stacks+0x22f/0x380 kernel/rcu/tree_stall.h:349
print_cpu_stall+0x31d/0x5f0 kernel/rcu/tree_stall.h:633
check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
rcu_pending kernel/rcu/tree.c:3936 [inline]
rcu_sched_clock_irq+0x6d8/0x1110 kernel/rcu/tree.c:2619
update_process_times+0x193/0x200 kernel/time/timer.c:1818
tick_sched_handle kernel/time/tick-sched.c:254 [inline]
tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
__run_hrtimer kernel/time/hrtimer.c:1685 [inline]
__hrtimer_run_queues+0x4fe/0xc40 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_acquire+0x1f2/0x3f0 kernel/locking/lockdep.c:5627
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f6 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 66 43 c7 44 3d 09 00 00 43 c6 44 3d 0b
RSP: 0018:ffffc9000389f0a0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000001 RCX: 197cb7d189095900
RDX: 0000000000000000 RSI: ffffffff8a0b2e80 RDI: ffffffff8a59e800
RBP: ffffc9000389f1a8 R08: dffffc0000000000 R09: fffffbfff1ff5419
R10: fffffbfff1ff5419 R11: 1ffffffff1ff5418 R12: ffffffff8c1b9cb0
R13: 1ffff92000713e20 R14: 0000000000000246 R15: dffffc0000000000
down_read_trylock+0x206/0x370 kernel/locking/rwsem.c:1540
shrink_slab_memcg mm/vmscan.c:807 [inline]
shrink_slab+0x201/0x770 mm/vmscan.c:913
shrink_node_memcgs mm/vmscan.c:2958 [inline]
shrink_node+0x110c/0x2610 mm/vmscan.c:3079
shrink_zones mm/vmscan.c:3285 [inline]
do_try_to_free_pages+0x5da/0x15c0 mm/vmscan.c:3340
try_to_free_mem_cgroup_pages+0x2f6/0x780 mm/vmscan.c:3654
try_charge_memcg+0x3de/0x14a0 mm/memcontrol.c:2654
obj_cgroup_charge_pages+0x87/0x190 mm/memcontrol.c:3018
__memcg_kmem_charge_page+0x2fe/0x380 mm/memcontrol.c:3058
__alloc_pages+0x218/0x470 mm/page_alloc.c:5504
__get_free_pages+0x8/0x30 mm/page_alloc.c:5524
io_mem_alloc io_uring/io_uring.c:8875 [inline]
io_allocate_scq_urings io_uring/io_uring.c:10314 [inline]
io_uring_create io_uring/io_uring.c:10412 [inline]
io_uring_setup io_uring/io_uring.c:10502 [inline]
__do_sys_io_uring_setup io_uring/io_uring.c:10508 [inline]
__se_sys_io_uring_setup+0x112d/0x2850 io_uring/io_uring.c:10505
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: 0033:0x7f7fe24ce749
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:00007f7fe0713fc8 EFLAGS: 00000202 ORIG_RAX: 00000000000001a9
RAX: ffffffffffffffda RBX: 00007f7fe2725090 RCX: 00007f7fe24ce749
RDX: 0000000000000000 RSI: 0000200000000340 RDI: 0000000000000111
RBP: 0000200000000340 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000111 R15: 0000000000000000
</TASK>


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