[syzbot] [io-uring?] INFO: rcu detected stall in io_ring_exit_work (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f0b9d8eb98df Merge tag 'nfsd-6.19-3' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17eba922580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a11e0f726bfb6765
dashboard link: https://syzkaller.appspot.com/bug?extid=33504742c13bcd6c9541
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4dbba2a806a3/disk-f0b9d8eb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2a52c0f94de7/vmlinux-f0b9d8eb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5ddf9a24988b/bzImage-f0b9d8eb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+335047...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P7809/1:b..l
rcu: (detected by 0, t=10503 jiffies, g=47705, q=685 ncpus=2)
task:kworker/u8:22 state:R running task stack:23544 pid:7809 tgid:7809 ppid:2 task_flags:0x4208060 flags:0x00080000
Workqueue: iou_exit io_ring_exit_work
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5256 [inline]
__schedule+0x1139/0x6150 kernel/sched/core.c:6863
preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7190
irqentry_exit+0x1d8/0x8c0 kernel/entry/common.c:216
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:unwind_next_frame+0x162b/0x20b0 arch/x86/kernel/unwind_orc.c:680
Code: 00 00 fc ff df 80 3c 02 00 0f 84 31 f8 ff ff 4c 89 e7 e8 58 f3 bb 00 e9 24 f8 ff ff 48 b8 00 00 00 00 00 fc ff df 48 8b 14 24 <48> c1 ea 03 80 3c 02 00 0f 85 a8 05 00 00 49 8d 7d 08 49 8b 5d 38
RSP: 0018:ffffc9000c7e7558 EFLAGS: 00000246
RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffc9000c7e8000
RDX: ffffc9000c7e7600 RSI: ffffc9000c7e79e0 RDI: ffffc9000c7e7608
RBP: ffffc9000c7e7bd0 R08: 0000000000000001 R09: 0000000077ba390a
R10: 0000000000000002 R11: 000000000003a058 R12: ffffc9000c7e7618
R13: ffffc9000c7e75c8 R14: ffffc9000c7e7a10 R15: ffffc9000c7e75fc
arch_stack_walk+0x94/0x100 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
kasan_save_stack+0x33/0x60 mm/kasan/common.c:57
kasan_save_track+0x14/0x30 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
kmalloc_noprof include/linux/slab.h:957 [inline]
slab_free_hook mm/slub.c:2492 [inline]
slab_free mm/slub.c:6670 [inline]
kmem_cache_free+0x147/0x770 mm/slub.c:6781
__io_req_caches_free+0x19e/0x5c0 io_uring/io_uring.c:2827
io_req_caches_free io_uring/io_uring.c:2839 [inline]
io_ring_exit_work+0x33c/0x1170 io_uring/io_uring.c:3025
process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257
process_scheduled_works kernel/workqueue.c:3340 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>
rcu: rcu_preempt kthread starved for 10528 jiffies! g47705 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:28328 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5256 [inline]
__schedule+0x1139/0x6150 kernel/sched/core.c:6863
__schedule_loop kernel/sched/core.c:6945 [inline]
schedule+0xe7/0x3a0 kernel/sched/core.c:6960
schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x1ea/0xaf0 kernel/rcu/tree.c:2083
rcu_gp_kthread+0x26d/0x380 kernel/rcu/tree.c:2285
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 12129 Comm: syz.5.1498 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x29/0x50 kernel/locking/spinlock.c:202
Code: 90 f3 0f 1e fa 53 48 8b 74 24 08 48 89 fb 48 83 c7 18 e8 7a fe 1e f6 48 89 df e8 32 51 1f f6 e8 9d 14 4c f6 fb bf 01 00 00 00 <e8> 42 54 0f f6 65 8b 05 9b b9 37 08 85 c0 74 06 5b e9 01 4d 00 00
RSP: 0018:ffffc9000ec8fca0 EFLAGS: 00000202
RAX: 0000000007584837 RBX: ffff888031ace5c0 RCX: ffffffff81c70a2f
RDX: 0000000000000000 RSI: ffffffff8dace031 RDI: 0000000000000001
RBP: ffff888031ace9c0 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff9088b8d7 R11: ffff88802bec0b30 R12: 0000000000000000
R13: 0000000000000021 R14: 0000000000000400 R15: ffff888031ace5c0
FS: 00007fc1128de6c0(0000) GS:ffff8881248f5000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc1128de040 CR3: 0000000043610000 CR4: 00000000003526f0
Call Trace:
<TASK>
spin_unlock_irq include/linux/spinlock.h:401 [inline]
get_signal+0x1e6a/0x26d0 kernel/signal.c:3037
arch_do_signal_or_restart+0x8f/0x7e0 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
exit_to_user_mode_loop+0x8c/0x540 kernel/entry/common.c:75
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
do_syscall_64+0x4ee/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc11198f747
Code: ff ff 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
RSP: 002b:00007fc1128de0e8 EFLAGS: 00000246
RAX: 00000000000000ca RBX: 00007fc111be6098 RCX: 00007fc11198f749
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fc111be6098
RBP: 00007fc111be6090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc111be6128 R14: 00007fff61d0e6b0 R15: 00007fff61d0e798
</TASK>


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