syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P144/1:b..l P6452/1:b..l
	(detected by 0, t=10502 jiffies, g=25537, q=214)
task:syz-executor    state:R  running task     stack:28096 pid: 6452 ppid:  5697 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5027 [inline]
 __schedule+0x12c4/0x45b0 kernel/sched/core.c:6373
 preempt_schedule_common+0x83/0xd0 kernel/sched/core.c:6549
 preempt_schedule+0xd9/0xe0 kernel/sched/core.c:6574
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
 __raw_spin_unlock include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock+0x36/0x40 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:403 [inline]
 filemap_map_pages+0x122d/0x15c0 mm/filemap.c:3353
 do_fault_around mm/memory.c:4213 [inline]
 do_read_fault mm/memory.c:4228 [inline]
 do_fault mm/memory.c:4362 [inline]
 handle_pte_fault mm/memory.c:4620 [inline]
 __handle_mm_fault mm/memory.c:4755 [inline]
 handle_mm_fault+0x341b/0x5960 mm/memory.c:4853
 do_user_addr_fault arch/x86/mm/fault.c:1357 [inline]
 handle_page_fault arch/x86/mm/fault.c:1445 [inline]
 exc_page_fault+0x271/0x700 arch/x86/mm/fault.c:1501
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:568
RIP: 0033:0x7f69515e5307
RSP: 002b:00007fff8fd59b10 EFLAGS: 00010246
RAX: 000000000000004c RBX: 00007fff8fd5a070 RCX: 00007f69516cdac0
RDX: 0000000000000000 RSI: 00007f69516ad892 RDI: 00007fff8fd5a350
RBP: 0000000000000016 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000000 R12: 000000000000006c
R13: 00007fff8fd5a1f0 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
task:kworker/u4:1    state:R  running task     stack:21152 pid:  144 ppid:     2 flags:0x00004000
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5027 [inline]
 __schedule+0x12c4/0x45b0 kernel/sched/core.c:6373
 preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6777
 irqentry_exit+0x53/0x80 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:638
RIP: 0010:debug_lockdep_rcu_enabled+0x0/0x30 kernel/rcu/update.c:279
Code: 5d 41 b5 03 00 75 e7 48 c7 c7 a0 29 8b 8a 48 c7 c6 60 4e 8b 8a e8 50 b1 17 f7 0f 0b eb d0 cc cc cc cc cc cc cc cc cc cc cc cc <31> c0 83 3d ab 0e b5 03 00 74 1d 83 3d 22 41 b5 03 00 74 14 65 48
RSP: 0018:ffffc900015dfa58 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000033574 RCX: ffff88801c103b80
RDX: 0000000000000000 RSI: 0000000000033574 RDI: 0000000000033574
RBP: ffffc900015dfb70 R08: ffffffff88d346cb R09: fffffbfff20e2419
R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff920002bbf62
R13: 0000000000033574 R14: dffffc0000000000 R15: ffff88814b19aba0
 rcu_read_unlock include/linux/rcupdate.h:768 [inline]
 inet_twsk_purge+0x8a1/0x9d0 net/ipv4/inet_timewait_sock.c:309
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x763/0xb60 net/core/net_namespace.c:599
 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: rcu_preempt kthread starved for 10410 jiffies! g25537 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:26432 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5027 [inline]
 __schedule+0x12c4/0x45b0 kernel/sched/core.c:6373
 schedule+0x11b/0x1f0 kernel/sched/core.c:6456
 schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x2bf/0x1080 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0xa4/0x360 kernel/rcu/tree.c:2145
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </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 acpi_safe_halt drivers/acpi/processor_idle.c:108 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_idle_do_entry+0x10f/0x340 drivers/acpi/processor_idle.c:562