[v6.1] INFO: rcu detected stall in pcpu_balance_workfn

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8ce36b2849ef Linux 6.1.163
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11440722580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0605c5af04d7603
dashboard link: https://syzkaller.appspot.com/bug?extid=1d22c8733c47a1225458
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/25d3bb1313db/disk-8ce36b28.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/53d3c77e16da/vmlinux-8ce36b28.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ca171a78e481/bzImage-8ce36b28.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1d22c8...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P4270/1:b..l P5162/1:b..l
(detected by 0, t=10502 jiffies, g=33241, q=44 ncpus=2)
task:kworker/1:8 state:R running task stack:21712 pid:5162 ppid:2 flags:0x00004000
Workqueue: events pcpu_balance_workfn
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5245 [inline]
__schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6874
irqentry_exit+0x63/0x70 kernel/entry/common.c:439
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:lock_acquire+0x225/0x4a0 kernel/locking/lockdep.c:5666
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3d 04 f8 0f 85 f0 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 43 c7 44 3d 08 00 00 00 00 65 48 8b 04
RSP: 0018:ffffc90002fb78a0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 40e076cbaa3a0b00
RDX: 0000000000000000 RSI: ffffffff8a8c23a0 RDI: ffffffff8adf0d20
RBP: ffffc90002fb79a8 R08: dffffc0000000000 R09: 1ffffffff215ea48
R10: dffffc0000000000 R11: fffffbfff215ea49 R12: 0000000000000001
R13: 1ffff920005f6f20 R14: 0000000000000246 R15: dffffc0000000000
rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
rcu_read_lock include/linux/rcupdate.h:791 [inline]
page_ext_get+0x3a/0x2a0 mm/page_ext.c:157
__page_table_check_zero+0x134/0x4b0 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+0x8c4/0x9a0 mm/page_alloc.c:3413
free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3508
pcpu_free_pages mm/percpu-vm.c:65 [inline]
pcpu_depopulate_chunk+0x40f/0x4c0 mm/percpu-vm.c:330
pcpu_reclaim_populated mm/percpu.c:2193 [inline]
pcpu_balance_workfn+0x384/0x11a0 mm/percpu.c:2250
process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
task:syz-executor state:R running task stack:22064 pid:4270 ppid:4264 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5245 [inline]
__schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6731
preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6755
preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
unwind_next_frame+0x1892/0x20b0 arch/x86/kernel/unwind_orc.c:629
arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
save_stack+0x121/0x230 mm/page_owner.c:127
__reset_page_owner+0x51/0x1a0 mm/page_owner.c:148
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1486 [inline]
free_pcp_prepare mm/page_alloc.c:1536 [inline]
free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3413
free_unref_page_list+0xbb/0x8e0 mm/page_alloc.c:3554
release_pages+0x1fa6/0x2220 mm/swap.c:1035
__pagevec_release+0x6d/0xe0 mm/swap.c:1055
pagevec_release include/linux/pagevec.h:71 [inline]
folio_batch_release include/linux/pagevec.h:135 [inline]
shmem_undo_range+0x7c2/0x20c0 mm/shmem.c:946
shmem_truncate_range mm/shmem.c:1062 [inline]
shmem_evict_inode+0x25b/0xa80 mm/shmem.c:1171
evict+0x4c9/0x8d0 fs/inode.c:705
do_unlinkat+0x388/0x580 fs/namei.c:4405
__do_sys_unlink fs/namei.c:4446 [inline]
__se_sys_unlink fs/namei.c:4444 [inline]
__x64_sys_unlink+0x45/0x50 fs/namei.c:4444
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe87039b067
RSP: 002b:00007ffd709e5128 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fe87039b067
RDX: 00007ffd709e5150 RSI: 00007ffd709e51e0 RDI: 00007ffd709e51e0
RBP: 00007ffd709e51e0 R08: 00007ffd709e61e0 R09: 00000000ffffffff
R10: 0000000000000100 R11: 0000000000000206 R12: 00007ffd709e6270
R13: 00007fe870431c3b R14: 000000000006ae8d R15: 00007ffd709e62b0
</TASK>
rcu: rcu_preempt kthread starved for 10562 jiffies! g33241 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:28016 pid:16 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5245 [inline]
__schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
schedule+0xb9/0x180 kernel/sched/core.c:6638
schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168
rcu_gp_fqs_loop+0x303/0x1340 kernel/rcu/tree.c:1706
rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:741


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