echo w >/proc/sysrq-trigger

dmesg
[4680785.899872] Show Blocked State
[4680785.900063] task taskaddr stack pid father veid
[4680785.900223] lxc-start D ffff8802eed94640 0 74111 68892 113 0x00000084
[4680785.900228] ffff88008d5b3c18 0000000000000086 0000000000000000 ffff8804212a74c8
[4680785.900233] ffff88008d5b3b98 ffffffff811e374c 00109c9dbec7d9ab ffff8804212a7400
[4680785.900237] ffff8804212a74c8 0000000000000000 0000000216c01c50 00000000000004b4
[4680785.900241] Call Trace:
[4680785.900248] [] ? dispose_list+0xfc/0x120
[4680785.900253] [] fsnotify_unmount+0x1d5/0x270
[4680785.900258] [] ? autoremove_wake_function+0x0/0x40
[4680785.900262] [] fsnotify_unmount_mnt+0x29/0x40
[4680785.900267] [] mntput_no_expire+0xf3/0x110
[4680785.900270] [] release_mounts+0xa9/0xc0
[4680785.900274] [] put_mnt_ns+0x98/0xc0
[4680785.900278] [] ? proc_delete_inode+0x0/0xa0
[4680785.900281] [] mntns_put+0xe/0x10
[4680785.900284] [] proc_delete_inode+0x8e/0xa0
[4680785.900288] [] generic_delete_inode+0xd8/0x1d0
[4680785.900291] [] iput+0xc9/0x110
[4680785.900294] [] dentry_iput+0xa0/0x110
[4680785.900298] [] d_kill+0x3c/0x70
[4680785.900301] [] dput_nocache+0xf6/0x260
[4680785.900304] [] dput+0x10/0x20
[4680785.900308] [] __fput+0x1d7/0x290
[4680785.900312] [] fput+0x25/0x30
[4680785.900315] [] filp_close+0x60/0x90
[4680785.900319] [] sys_close+0xa5/0x100
[4680785.900324] [] system_call_fastpath+0x2f/0x34