syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P11550/1:b..l
	(detected by 0, t=10502 jiffies, g=54989, q=54 ncpus=2)
task:syz.4.2579      state:R  running task     stack:23752 pid:11550 ppid:4257   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6561
 preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6873
 irqentry_exit+0x53/0x80 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:lock_acquire+0x26f/0x5a0 kernel/locking/lockdep.c:5666
Code: 2b 00 74 08 4c 89 f7 e8 af 54 77 00 f6 44 24 61 02 0f 85 84 01 00 00 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 40 0e 36 e0 45 <4b> c7 44 25 00 00 00 00 00 43 c7 44 25 09 00 00 00 00 43 c7 44 25
RSP: 0018:ffffc9000d06f020 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 1ffff92001a0de10 RCX: 1ffff92001a0ddb0
RDX: dffffc0000000000 RSI: ffffffff8b0c2f40 RDI: ffffffff8b5f70e0
RBP: ffffc9000d06f180 R08: dffffc0000000000 R09: fffffbfff225764d
R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff92001a0de0c
R13: dffffc0000000000 R14: ffffc9000d06f080 R15: 0000000000000246
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock include/linux/rcupdate.h:791 [inline]
 blk_cgroup_congested+0x36/0x220 block/blk-cgroup.c:2002
 __cgroup_throttle_swaprate+0x6d/0x1b0 mm/swapfile.c:3671
 cgroup_throttle_swaprate include/linux/swap.h:662 [inline]
 wp_page_copy+0x461/0x18c0 mm/memory.c:3179
 handle_pte_fault mm/memory.c:5049 [inline]
 __handle_mm_fault mm/memory.c:5173 [inline]
 handle_mm_fault+0x2525/0x5340 mm/memory.c:5294
 do_user_addr_fault arch/x86/mm/fault.c:1340 [inline]
 handle_page_fault arch/x86/mm/fault.c:1431 [inline]
 exc_page_fault+0x26f/0x620 arch/x86/mm/fault.c:1487
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0010:copy_user_enhanced_fast_string+0xa/0x40 arch/x86/lib/copy_user_64.S:166
Code: ff c9 75 f2 89 d1 c1 e9 03 83 e2 07 f3 48 a5 89 d1 f3 a4 31 c0 0f 01 ca c3 8d 0c ca 89 ca eb 20 0f 01 cb 83 fa 40 72 38 89 d1 <f3> a4 31 c0 0f 01 ca c3 89 ca eb 0a 66 2e 0f 1f 84 00 00 00 00 00
RSP: 0018:ffffc9000d06f790 EFLAGS: 00050206
RAX: ffffffff8441ba01 RBX: 00007ffffffeee30 RCX: 0000000000007e83
RDX: 00000000000101d0 RSI: ffff88804cd08435 RDI: 0000200000c8f000
RBP: ffffc9000d06f910 R08: dffffc0000000000 R09: ffffed10099a2057
R10: 0000000000000007 R11: dffffc0000000001 R12: 00000000000101d0
R13: 0000000000000000 R14: 0000200000c86cb3 R15: ffff88804cd000e8
 copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
 raw_copy_to_user arch/x86/include/asm/uaccess_64.h:58 [inline]
 copyout+0xd8/0x120 lib/iov_iter.c:170
 _copy_to_iter+0x4a6/0x1000 lib/iov_iter.c:527
 __skb_datagram_iter+0xdd/0x7c0 net/core/datagram.c:419
 skb_copy_datagram_iter+0xe1/0x2b0 net/core/datagram.c:535
 skb_copy_datagram_msg include/linux/skbuff.h:3956 [inline]
 tipc_recvstream+0x7a4/0xf70 net/tipc/socket.c:2071
 ____sys_recvmsg+0x285/0x530 net/socket.c:-1
 ___sys_recvmsg net/socket.c:2780 [inline]
 __sys_recvmsg+0x2e9/0x3d0 net/socket.c:2810
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f377358d169
RSP: 002b:00007f3774452038 EFLAGS: 00000246 ORIG_RAX: 000000000000002f
RAX: ffffffffffffffda RBX: 00007f37737a5fa0 RCX: 00007f377358d169
RDX: 0000000000001f00 RSI: 0000200000000500 RDI: 000000000000000b
RBP: 00007f377360e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f37737a5fa0 R15: 00007ffcf7d65ec8
 </TASK>
rcu: rcu_preempt kthread starved for 10552 jiffies! g54989 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:26712 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6561
 schedule+0xbf/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2d2/0x1150 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0xa3/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x28d/0x320 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 acpi_safe_halt drivers/acpi/processor_idle.c:111 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_idle_do_entry+0x10f/0x340 drivers/acpi/processor_idle.c:567
sched: RT throttling activated
hrtimer: interrupt took 742398792 ns