rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 GPs behind) idle=fb24/1/0x4000000000000000 softirq=112152/112157 fqs=301
rcu: 	(detected by 0, t=10505 jiffies, g=60261, q=410 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 19232 Comm: syz.2.4101 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:mm_get_cid+0xab/0x130
Code: 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 49 c7 c5 c8 84 d8 8d 49 c1 ed 03 bd 00 00 00 80 eb 07 44 89 f0 f7 d8 71 d4 f3 90 <43> 0f b6 44 25 00 84 c0 75 41 44 8b 3d 6c 2d 45 0c 48 89 df 4c 89
RSP: 0018:ffffc900052e7028 EFLAGS: 00000887
RAX: 0000000080000000 RBX: ffff8881a8440b90 RCX: dffffc0000000000
RDX: 0000000000000002 RSI: 0000000000000002 RDI: ffff8881a8440b90
RBP: 0000000080000000 R08: ffff8881a8440a13 R09: 1ffff11035088142
R10: dffffc0000000000 R11: ffffed1035088143 R12: dffffc0000000000
R13: 1ffffffff1bb1099 R14: 0000000080000000 R15: 0000000000000002
FS:  00007f27e3b296c0(0000) GS:ffff8882a9918000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f27e2be8400 CR3: 000000016ae92000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 __schedule+0x21b0/0x4fb0
 schedule+0x164/0x360
 schedule_preempt_disabled+0x13/0x30
 rwsem_down_write_slowpath+0x899/0x1040
 down_write+0x1bc/0x200
 kernfs_add_one+0x2ae/0x5c0
 __kernfs_create_file+0x22b/0x2e0
 sysfs_add_file_mode_ns+0x238/0x300
 internal_create_group+0x673/0x1180
 sysfs_create_groups+0x59/0x120
 ib_setup_port_attrs+0x148f/0x2140
 add_one_compat_dev+0x448/0x650
 rdma_dev_init_net+0x243/0x2f0
 ops_init+0x35c/0x5c0
 setup_net+0x118/0x340
 copy_net_ns+0x3e2/0x570
 create_new_namespaces+0x3e7/0x6a0
 unshare_nsproxy_namespaces+0x11a/0x160
 ksys_unshare+0x4f4/0x900
 __x64_sys_unshare+0x38/0x50
 do_syscall_64+0xe2/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f27e2b9acb9
Code: Unable to access opcode bytes at 0x7f27e2b9ac8f.
RSP: 002b:00007f27e3b29028 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007f27e2e15fa0 RCX: 00007f27e2b9acb9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000006a040000
RBP: 00007f27e2c08bf7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f27e2e16038 R14: 00007f27e2e15fa0 R15: 00007ffd394cff78
 </TASK>
rcu: rcu_preempt kthread starved for 9000 jiffies! g60261 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:28080 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 __schedule+0x14ef/0x4fb0
 schedule+0x164/0x360
 schedule_timeout+0x158/0x2c0
 rcu_gp_fqs_loop+0x312/0x1560
 rcu_gp_kthread+0x9d/0x3b0
 kthread+0x726/0x8b0
 ret_from_fork+0x51b/0xa40
 ret_from_fork_asm+0x1a/0x30
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 5737 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:smp_call_function_many_cond+0xcea/0x1270
Code: 89 ee 83 e6 01 31 ff e8 94 b4 0b 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 3f b0 0b 00 eb 38 f3 90 42 0f b6 04 2b <84> c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 23 b0 0b 00 eb e4 44
RSP: 0018:ffffc900048f7600 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 1ffff110478c8129 RCX: ffff88810e1357c0
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900048f7740 R08: ffffffff8fcf3677 R09: 1ffffffff1f9e6ce
R10: dffffc0000000000 R11: fffffbfff1f9e6cf R12: ffff88823c640948
R13: dffffc0000000000 R14: ffff88812103bb00 R15: 0000000000000001
FS:  000055557d9f0500(0000) GS:ffff88818e318000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff2f411eff8 CR3: 0000000106a8e000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3f/0x80
 flush_tlb_mm_range+0x5c3/0x10c0
 tlb_flush_mmu+0x1a5/0x680
 tlb_finish_mmu+0xf9/0x230
 vms_clear_ptes+0x44d/0x570
 vms_complete_munmap_vmas+0x205/0x890
 do_vmi_align_munmap+0x3b7/0x4b0
 do_vmi_munmap+0x252/0x2d0
 __vm_munmap+0x22c/0x3d0
 __x64_sys_munmap+0x60/0x70
 do_syscall_64+0xe2/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff2f319aae7
Code: 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc8f9b9db8 EFLAGS: 00000202 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffda RBX: 0000000000009000 RCX: 00007ff2f319aae7
RDX: 00007ff2f31984f0 RSI: 0000000000009000 RDI: 00007ff2f4116000
RBP: 00007ff2f4116000 R08: 0000000000004b27 R09: 0000000000000000
R10: 0000000000000008 R11: 0000000000000202 R12: 00007ffc8f9b9e60
R13: 0000000000000000 R14: 0000000000000a01 R15: 0000000000000000
 </TASK>
