[v6.6] INFO: rcu detected stall in schedule_tail

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c09fbcd31ae6 Linux 6.6.130
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16ed946a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5b35c4db8465904
dashboard link: https://syzkaller.appspot.com/bug?extid=54b8bc61bf25fcbb8722
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=129915da580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=170388f2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/58165bbf9941/disk-c09fbcd3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/73cbb84fb36b/vmlinux-c09fbcd3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/744ea33ec44b/bzImage-c09fbcd3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+54b8bc...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P5792/1:b..l
rcu: (detected by 1, t=10503 jiffies, g=8841, q=23 ncpus=2)
task:syz-executor401 state:R running task stack:28680 pid:5792 ppid:5770 flags:0x00004002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x1553/0x45a0 kernel/sched/core.c:6700
preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
irqentry_exit+0x67/0x70 kernel/entry/common.c:438
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_is_held_type+0x13e/0x190 kernel/locking/lockdep.c:5830
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:ffffc90004787940 EFLAGS: 00000206
RAX: 9b955fa08a09f200 RBX: ffff888024ec0000 RCX: 9b955fa08a09f200
RDX: 0000000000000000 RSI: ffffffff8acadb60 RDI: ffffffff8b1c89a0
RBP: 0000000000000000 R08: dffffc0000000000 R09: 1ffffffff22386a0
R10: dffffc0000000000 R11: fffffbfff22386a1 R12: 0000000000000002
R13: 0000000000000246 R14: ffffffff8d15bb78 R15: ffff888024ec0b30
lock_is_held include/linux/lockdep.h:288 [inline]
task_css include/linux/cgroup.h:436 [inline]
mem_cgroup_from_task+0x77/0x110 mm/memcontrol.c:1038
get_mem_cgroup_from_mm+0xd6/0x290 mm/memcontrol.c:1091
__mem_cgroup_charge+0x15/0x80 mm/memcontrol.c:7110
mem_cgroup_charge include/linux/memcontrol.h:686 [inline]
wp_page_copy mm/memory.c:3118 [inline]
do_wp_page+0x14b0/0x35f0 mm/memory.c:3469
handle_pte_fault mm/memory.c:5063 [inline]
__handle_mm_fault mm/memory.c:5188 [inline]
handle_mm_fault+0x135d/0x4c00 mm/memory.c:5353
do_user_addr_fault+0x730/0x12c0 arch/x86/mm/fault.c:1371
handle_page_fault arch/x86/mm/fault.c:1463 [inline]
exc_page_fault+0x64/0x100 arch/x86/mm/fault.c:1516
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0010:__put_user_4+0x11/0x20 arch/x86/lib/putuser.S:89
Code: 01 ca c3 90 90 90 90 90 90 f3 0f 1e fa 0f 01 cb 66 89 01 31 c9 0f 01 ca c3 f3 0f 1e fa 48 89 cb 48 c1 fb 3f 48 09 d9 0f 01 cb <89> 01 31 c9 0f 01 ca c3 90 90 90 90 90 90 90 f3 0f 1e fa 0f 01 cb
RSP: 0018:ffffc90004787ef8 EFLAGS: 00050206
RAX: 0000000000000003 RBX: 0000000000000000 RCX: 0000555578759690
RDX: 0000000000000000 RSI: ffffffff8acadb60 RDI: ffffffff8b1c89a0
RBP: 0000000000000000 R08: ffffffff8e8b02af R09: 1ffffffff1d16055
R10: dffffc0000000000 R11: fffffbfff1d16056 R12: 1ffff110049d80d2
R13: 0000000000000000 R14: ffff888024ec0000 R15: dffffc0000000000
schedule_tail+0x93/0xb0 kernel/sched/core.c:5316
ret_from_fork+0x24/0x80 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
rcu: rcu_preempt kthread starved for 10533 jiffies! g8841 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:27656 pid:17 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x1553/0x45a0 kernel/sched/core.c:6700
schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 5791 Comm: syz-executor401 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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: 00 f3 0f 1e fa 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 5a fd d8 f6 48 89 df e8 12 d2 d9 f6 e8 dd e2 fd f6 fb bf 01 00 00 00 <e8> f2 d8 cc f6 65 8b 05 63 06 74 75 85 c0 74 02 5b c3 e8 e0 ed 70
RSP: 0018:ffffc90004777c78 EFLAGS: 00000286
RAX: bd3287ca134bc100 RBX: ffff88802abedc80 RCX: bd3287ca134bc100
RDX: dffffc0000000000 RSI: ffffffff8acac9e0 RDI: 0000000000000001
RBP: ffff88802abee118 R08: ffffffff8e8b02af R09: 1ffffffff1d16055
R10: dffffc0000000000 R11: fffffbfff1d16056 R12: 1ffff1100557dc23
R13: 0000000000000021 R14: dffffc0000000000 R15: 0000000000000000
FS: 00005555787593c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000bbdffc CR3: 000000002eab7000 CR4: 00000000003506e0
Call Trace:
<TASK>
spin_unlock_irq include/linux/spinlock.h:401 [inline]
get_signal+0x11f5/0x13f0 kernel/signal.c:2905
arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fbc211c6bee
Code: 08 0f 85 45 e1 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 90 41 57 41 56 4d 89 c6 41 55 4d 89 cd 41 54 55 53 48 83 ec 08
RSP: 002b:00007ffd512d1f98 EFLAGS: 00000246
RAX: fffffffffffffff7 RBX: 00005555787593c0 RCX: 00007fbc211c6bee
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000013
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fbc212300b2
R13: 00007fbc2122e12a R14: 00007ffd512d2030 R15: 0000000000000000
</TASK>


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