It seems we have the same problem with latest LTS kernel

# uname -a
Linux dc01ram1rls 4.4.0-18-generic #34~14.04.1-Ubuntu SMP Thu Apr 7 18:31:54 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

# lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 14.04.4 LTS
Release:	14.04
Codename:	trusty

The kernel was installed with 
# apt-get install --install-recommends linux-generic-lts-xenial

Errors in /var/log/kern.log look like:

Apr 24 03:31:58 dc01ram1rls kernel: [280174.661115] NMI watchdog: BUG: soft lockup - CPU#4 stuck for 22s! [rsync:10
4799]
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669494] Modules linked in: ip6table_filter ip6_tables iptable_filter ip
_tables ebtable_nat ebtables x_tables 8021q garp mrp bridge stp llc dm_crypt intel_rapl ipmi_ssif x86_pkg_temp_ther
mal intel_powerclamp ipmi_devintf coretemp kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul aesni_intel aes_x8
6_64 lrw gf128mul glue_helper ablk_helper sb_edac cryptd dcdbas edac_core input_leds mei_me lpc_ich mei ipmi_si 825
0_fintek shpchp ipmi_msghandler acpi_power_meter mac_hid parport_pc ppdev lp parport igb dca ptp hid_generic usbhid
 uas hid usb_storage ahci pps_core megaraid_sas i2c_algo_bit libahci wmi fjes
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669522] CPU: 4 PID: 104799 Comm: rsync Not tainted 4.4.0-18-generic #34
~14.04.1-Ubuntu
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669523] Hardware name: Dell Inc. PowerEdge T630/0W9WXC, BIOS 1.3.6 06/0
8/2015
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669525] task: ffff88041ebea940 ti: ffff880402580000 task.ti: ffff880402
580000
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669526] RIP: 0010:[<ffffffff810c4e50>]  [<ffffffff810c4e50>] native_que
ued_spin_lock_slowpath+0x160/0x170
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669531] RSP: 0018:ffff8804025839f8  EFLAGS: 00000202
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669532] RAX: 0000000000000101 RBX: 0000000000000000 RCX: 00000000000000
01
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669533] RDX: 0000000000000101 RSI: 0000000000000001 RDI: ffffffff81fce3
20
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669533] RBP: ffff8804025839f8 R08: 0000000000000101 R09: ffff880f9da4b7
a4
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669534] R10: ffff880855937000 R11: 000000000000008c R12: 00000000000000
00
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669535] R13: ffff880f9e2799f0 R14: ffff880f9e2799c0 R15: 00000000000000
00
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669536] FS:  00007f0980b0b740(0000) GS:ffff88085ec80000(0000) knlGS:000
0000000000000
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669537] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669538] CR2: 0000000002c0dd08 CR3: 0000000405421000 CR4: 00000000001426
e0
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669539] Stack:
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669539]  ffff880402583a08 ffffffff81180407 ffff880402583a18 ffffffff817
ee550
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669541]  ffff880402583a80 ffffffff8125ad4a 0000000000000000 ffff8804025
83a68
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669542]  ffffffff812332ab ffff880f9c044140 ffff880f9e2761a0 ffff8804025
83a70
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669544] Call Trace:
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669547]  [<ffffffff81180407>] queued_spin_lock_slowpath+0xb/0xf
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669550]  [<ffffffff817ee550>] _raw_spin_lock+0x20/0x30
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669552]  [<ffffffff8125ad4a>] mb_cache_entry_get+0x1aa/0x220
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669555]  [<ffffffff812332ab>] ? __getblk_gfp+0x2b/0x60
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669557]  [<ffffffff812c8efc>] ext4_xattr_block_set+0x7c/0x9d0
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669559]  [<ffffffff812c84e4>] ? ext4_xattr_set_entry+0x34/0x340
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669560]  [<ffffffff812ca3e2>] ext4_xattr_set_handle+0x2f2/0x420
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669562]  [<ffffffff812cf6d0>] __ext4_set_acl+0x280/0x320
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669564]  [<ffffffff812cfb42>] ext4_set_acl+0xd2/0x110
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669565]  [<ffffffff8125c0ad>] ? posix_acl_from_xattr+0x11d/0x170
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669567]  [<ffffffff8125c1b7>] posix_acl_xattr_set+0xb7/0x150
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669569]  [<ffffffff81221321>] generic_setxattr+0x61/0x80
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669570]  [<ffffffff81221e01>] __vfs_setxattr_noperm+0x61/0x1a0
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669573]  [<ffffffff81326c9d>] ? security_inode_setxattr+0xbd/0xd0
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669575]  [<ffffffff81221fe7>] vfs_setxattr+0xa7/0xb0
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669576]  [<ffffffff81222124>] setxattr+0x134/0x1c0
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669579]  [<ffffffff811db97f>] ? kmem_cache_alloc+0x19f/0x200
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669582]  [<ffffffff8120c1af>] ? getname_flags+0x4f/0x1f0
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669583]  [<ffffffff810c46ff>] ? percpu_down_read+0x1f/0x50
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669584]  [<ffffffff8122223c>] path_setxattr+0x8c/0xc0
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669586]  [<ffffffff812222f4>] SyS_setxattr+0x14/0x20
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669587]  [<ffffffff817ee8f6>] entry_SYSCALL_64_fastpath+0x16/0x75
Apr 24 03:31:58 dc01ram1rls kernel: [280174.669588] Code: 8b 01 48 85 c0 75 0a f3 90 48 8b 01 48 85 c0 74 f6 c7 40 08 01 00 00 00 e9 61 ff ff ff 83 fa 01 75 07 e9 c2 fe ff ff f3 90 8b 07 <84> c0 75 f8 b8 01 00 00 00 66 89 07 5d c3 66 90 0f 1f 44 00 00