syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P21630/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=136669, q=33 ncpus=2)
task:syz.4.4547      state:R  running task     stack:27912 pid:21630 ppid:18710  flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6700
 preempt_schedule_irq+0xb5/0x140 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:native_save_fl arch/x86/include/asm/irqflags.h:32 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:89 [inline]
RIP: 0010:arch_local_irq_save arch/x86/include/asm/irqflags.h:107 [inline]
RIP: 0010:lock_release+0x13b/0x8b0 kernel/locking/lockdep.c:5770
Code: 84 c0 0f 85 20 05 00 00 83 3b 00 0f 85 51 04 00 00 4c 89 74 24 10 48 c7 84 24 a0 00 00 00 00 00 00 00 9c 8f 84 24 a0 00 00 00 <48> 8b 84 24 a0 00 00 00 48 89 44 24 50 fa 48 c7 c7 20 c7 aa 8a e8
RSP: 0018:ffffc9000c3179c0 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff888021ac0adc RCX: f34bf7a6d1d58400
RDX: 0000000000000000 RSI: ffffffff8afc6760 RDI: ffffffff8afc6720
RBP: ffffc9000c317ac8 R08: ffffffff8e4a84ef R09: 1ffffffff1c9509d
R10: dffffc0000000000 R11: fffffbfff1c9509e R12: ffffffff81e4b465
R13: dffffc0000000000 R14: ffff888021ac0000 R15: 1ffff92001862f44
 rcu_lock_release include/linux/rcupdate.h:344 [inline]
 rcu_read_unlock include/linux/rcupdate.h:819 [inline]
 percpu_ref_tryget_many include/linux/percpu-refcount.h:250 [inline]
 percpu_ref_tryget+0xfd/0x180 include/linux/percpu-refcount.h:266
 obj_cgroup_tryget include/linux/memcontrol.h:793 [inline]
 __get_obj_cgroup_from_memcg+0x70/0xe0 mm/memcontrol.c:3014
 get_obj_cgroup_from_current+0x16f/0x280 mm/memcontrol.c:3034
 memcg_slab_pre_alloc_hook mm/slab.h:492 [inline]
 slab_pre_alloc_hook+0x95/0x310 mm/slab.h:719
 slab_alloc_node mm/slub.c:3467 [inline]
 slab_alloc mm/slub.c:3493 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3500 [inline]
 kmem_cache_alloc_lru+0x4d/0x2e0 mm/slub.c:3516
 alloc_inode_sb include/linux/fs.h:2946 [inline]
 alloc_inode fs/inode.c:263 [inline]
 new_inode_pseudo+0x82/0x1d0 fs/inode.c:1049
 new_inode+0x22/0x1b0 fs/inode.c:1075
 debugfs_get_inode fs/debugfs/inode.c:72 [inline]
 __debugfs_create_file+0x148/0x500 fs/debugfs/inode.c:431
 kvm_create_vm_debugfs+0x6c3/0x960 virt/kvm/kvm_main.c:1107
 kvm_create_vm virt/kvm/kvm_main.c:1242 [inline]
 kvm_dev_ioctl_create_vm virt/kvm/kvm_main.c:5090 [inline]
 kvm_dev_ioctl+0x128d/0x1640 virt/kvm/kvm_main.c:5132
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fdc3218ebe9
RSP: 002b:00007fdc33020038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fdc323b5fa0 RCX: 00007fdc3218ebe9
RDX: 0000000000000000 RSI: 000000000000ae01 RDI: 0000000000000003
RBP: 00007fdc32211e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdc323b6038 R14: 00007fdc323b5fa0 R15: 00007ffc97137d08
 </TASK>
rcu: rcu_preempt kthread starved for 10340 jiffies! g136669 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:26568 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 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: 0 PID: 0 Comm: swapper/0 Not tainted 6.6.101-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:148
Code: cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d 83 16 3b 00 f3 0f 1e fa fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc 66 0f 1f 00 55 41 57 41 56
RSP: 0018:ffffffff8ca07d80 EFLAGS: 000002c2
RAX: 4a8a3603a1d16900 RBX: ffffffff81619a6b RCX: 4a8a3603a1d16900
RDX: 0000000000000001 RSI: ffffffff8aaaba40 RDI: ffffffff8afc6780
RBP: ffffffff8ca07eb8 R08: ffff8880b8e36d4b R09: 1ffff110171c6da9
R10: dffffc0000000000 R11: ffffed10171c6daa R12: ffffffff8e4a84e8
R13: 0000000000000000 R14: 0000000000000000 R15: 1ffffffff1952670
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1a87314000 CR3: 000000002e3ea000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:753
 default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
 cpuidle_idle_call kernel/sched/idle.c:170 [inline]
 do_idle+0x1eb/0x510 kernel/sched/idle.c:282
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:380
 rest_init+0x2e2/0x300 init/main.c:732
 arch_call_rest_init+0xe/0x10 init/main.c:829
 start_kernel+0x459/0x4e0 init/main.c:1074
 x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:555
 x86_64_start_kernel+0x60/0x60 arch/x86/kernel/head64.c:536
 secondary_startup_64_no_verify+0x179/0x17b
 </TASK>