syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5711/1:b..l
	(detected by 0, t=10502 jiffies, g=17881, q=128 ncpus=2)
task:syz.0.473       state:R  running task     stack:25248 pid:5711  ppid:4267   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10e9/0x40d0 kernel/sched/core.c:6561
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6873
 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_is_held_type+0x13a/0x190 kernel/locking/lockdep.c:5710
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:ffffc900047377f8 EFLAGS: 00000206
RAX: 669abcd8c64e2700 RBX: ffff888076f7d940 RCX: 669abcd8c64e2700
RDX: ffffc9000cc09000 RSI: ffffffff8a8c15e0 RDI: ffffffff8adf1c20
RBP: 0000000000000000 R08: dffffc0000000000 R09: fffffbfff215c449
R10: fffffbfff215c449 R11: 1ffffffff215c448 R12: 0000000000000002
R13: 0000000000000246 R14: ffffffff8cb2ae60 R15: ffff888076f7e470
 lock_is_held include/linux/lockdep.h:283 [inline]
 rcu_read_lock_sched_held+0x86/0xf0 kernel/rcu/update.c:125
 task_css include/linux/cgroup.h:509 [inline]
 mem_cgroup_from_task+0x49/0x110 mm/memcontrol.c:985
 count_memcg_event_mm+0x196/0x3b0 include/linux/memcontrol.h:1096
 handle_mm_fault+0x122/0x3e70 mm/memory.c:5272
 faultin_page mm/gup.c:1026 [inline]
 __get_user_pages+0x3ff/0xeb0 mm/gup.c:1250
 populate_vma_page_range+0x214/0x2b0 mm/gup.c:1607
 __mm_populate+0x248/0x370 mm/gup.c:1721
 mm_populate include/linux/mm.h:2826 [inline]
 vm_mmap_pgoff+0x203/0x2b0 mm/util.c:525
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe5a458e929
RSP: 002b:00007fe5a53ef038 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007fe5a47b5fa0 RCX: 00007fe5a458e929
RDX: b635773f07ebbeeb RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007fe5a4610b39 R08: ffffffffffffffff R09: 0000000000002000
R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fe5a47b5fa0 R15: 00007ffe4ae39088
 </TASK>
rcu: rcu_preempt kthread starved for 5043 jiffies! g17881 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:26496 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10e9/0x40d0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x95/0x380 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