======================================
| [ 144.822356][ T73] #2: ffffffff9ab9de50 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net (net/core/net_namespace.c:594) 
| [ 144.822575][ T73] #3: ffff888003e93958 (&hashinfo->ehash_locks[i]){+.-.}-{2:2}, at: inet_twsk_deschedule_put (net/ipv4/inet_timewait_sock.c:243) 
| [  144.822821][   T73]
| [  144.822821][   T73] stack backtrace:
[  144.823152][   T73] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  144.823420][   T73] Workqueue: netns cleanup_net
[  144.823553][   T73] Call Trace:
[  144.823654][   T73]  <TASK>
[ 144.823718][ T73] dump_stack_lvl (lib/dump_stack.c:117) 
[ 144.823839][ T73] check_noncircular (kernel/locking/lockdep.c:2187) 
[ 144.823964][ T73] ? __pfx_check_noncircular (kernel/locking/lockdep.c:2163) 
[ 144.824094][ T73] ? __pfx_stack_trace_save (kernel/stacktrace.c:114) 
[ 144.824217][ T73] ? alloc_chain_hlocks (kernel/locking/lockdep.c:3501) 
[ 144.824340][ T73] check_prev_add (kernel/locking/lockdep.c:3135) 
[ 144.824463][ T73] validate_chain (kernel/locking/lockdep.c:3254 kernel/locking/lockdep.c:3869) 
[ 144.824590][ T73] ? __pfx_validate_chain (kernel/locking/lockdep.c:3825) 
[ 144.824712][ T73] ? hlock_class (./arch/x86/include/asm/bitops.h:227 ./arch/x86/include/asm/bitops.h:239 ./include/asm-generic/bitops/instrumented-non-atomic.h:142 kernel/locking/lockdep.c:228) 
[ 144.824838][ T73] ? mark_lock (kernel/locking/lockdep.c:4656 (discriminator 3)) 
[ 144.824933][ T73] __lock_acquire (kernel/locking/lockdep.c:5137) 
[ 144.825056][ T73] ? __lock_acquire (kernel/locking/lockdep.c:5133) 
[ 144.825181][ T73] ? __timer_delete_sync (kernel/time/timer.c:1648 (discriminator 1)) 
[ 144.825301][ T73] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5756) 
[ 144.825423][ T73] ? __timer_delete_sync (kernel/time/timer.c:1648 (discriminator 1)) 
[ 144.825544][ T73] ? inet_twsk_deschedule_put (net/ipv4/inet_timewait_sock.c:243) 
[ 144.825666][ T73] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 144.825792][ T73] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 52)) 
[ 144.825917][ T73] ? __timer_delete_sync (kernel/time/timer.c:1648 (discriminator 1)) 
[ 144.826037][ T73] ? lock_acquire (kernel/locking/lockdep.c:5727) 
[ 144.826157][ T73] ? __timer_delete_sync (kernel/time/timer.c:1648 (discriminator 1)) 
[ 144.826279][ T73] __timer_delete_sync (kernel/time/timer.c:1649 (discriminator 1)) 
[ 144.826399][ T73] ? __timer_delete_sync (kernel/time/timer.c:1648 (discriminator 1)) 
[ 144.826519][ T73] inet_twsk_deschedule_put (net/ipv4/inet_timewait_sock.c:243) 
[ 144.826638][ T73] ? inet_twsk_purge (./include/linux/rcupdate.h:339 ./include/linux/rcupdate.h:814 net/ipv4/inet_timewait_sock.c:328) 
[ 144.826761][ T73] inet_twsk_purge (net/ipv4/inet_timewait_sock.c:331) 
[ 144.826881][ T73] ? inet_twsk_purge (./include/linux/rcupdate.h:329 ./include/linux/rcupdate.h:781 net/ipv4/inet_timewait_sock.c:308) 
[ 144.827000][ T73] ? __pfx_inet_twsk_purge (net/ipv4/inet_timewait_sock.c:295) 
[ 144.827119][ T73] ? mark_lock (kernel/locking/lockdep.c:4656 (discriminator 3)) 
[ 144.827213][ T73] tcp_twsk_purge (net/ipv4/tcp_minisocks.c:402) 
[ 144.827333][ T73] tcp_sk_exit_batch (net/ipv4/tcp_ipv4.c:3507) 
[ 144.827455][ T73] cleanup_net (net/core/net_namespace.c:636 (discriminator 3)) 
[ 144.827576][ T73] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 144.827696][ T73] ? __pfx_cleanup_net (net/core/net_namespace.c:581) 
[ 144.827885][ T73] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 52)) 
[ 144.828005][ T73] ? process_one_work (kernel/workqueue.c:3230) 
[ 144.828125][ T73] ? lock_acquire (kernel/locking/lockdep.c:5727) 
[ 144.828245][ T73] ? process_one_work (kernel/workqueue.c:3230) 
[ 144.828431][ T73] process_one_work (kernel/workqueue.c:3254) 
[ 144.828552][ T73] ? __pfx___lock_release (kernel/locking/lockdep.c:5406) 
[ 144.828672][ T73] ? __pfx_process_one_work (kernel/workqueue.c:3156) 
[ 144.828796][ T73] ? assign_work (kernel/workqueue.c:1209) 
[ 144.828982][ T73] worker_thread (kernel/workqueue.c:3329 kernel/workqueue.c:3416) 
[ 144.829102][ T73] ? lockdep_hardirqs_on_prepare.part.0 (kernel/locking/lockdep.c:4300 kernel/locking/lockdep.c:4359) 
[ 144.829251][ T73] ? __pfx_worker_thread (kernel/workqueue.c:3362) 
[ 144.829370][ T73] ? __pfx_worker_thread (kernel/workqueue.c:3362) 
[ 144.829554][ T73] kthread (kernel/kthread.c:388) 
[ 144.829644][ T73] ? __pfx_kthread (kernel/kthread.c:341) 
[ 144.829763][ T73] ret_from_fork (arch/x86/kernel/process.c:147) 
[ 144.829886][ T73] ? __pfx_kthread (kernel/kthread.c:341) 


Finger prints:
dump_stack_lvl:check_noncircular:check_prev_add:validate_chain