BUG: warning at kernel/sched.c:4531/add_preempt_count()

At runtime we experience the following errors in dmesg:

BUG: warning at kernel/sched.c:4531/add_preempt_count()
 [<c101d646>] add_preempt_count+0x5c/0x79
 [<c136329b>] _spin_lock_irqsave+0xd/0x6c
BUG: using smp_processor_id() in preemptible [00000001] code: syslog-ng/8833
 [<c1044a49>] __sock_charge+0x64/0x1e8
caller is __call_console_drivers+0x2e/0x64
 [<c1044be9>] ub_tcp_sock_charge+0x1c/0x32
 [<c12a2882>] [<c1167caf>] sk_clone+0x1a8/0x227
debug_smp_processor_id+0x97/0xa8
 [<c12d6783>] [<c1026870>] inet_csk_clone+0xa/0x5b
__call_console_drivers+0x2e/0x64
 [<c12ec729>] [<c1027369>] do_release_console_sem+0x39/0x7a
tcp_create_openreq_child+0x1a/0x3e7
 [<c10273c2>] [<c12e95e7>] release_console_sem+0x18/0x51
tcp_v4_syn_recv_sock+0x42/0x370
 [<c11b12a3>] [<c1351d8d>] opost_block+0x10b/0x110
tcp_v6_syn_recv_sock+0x4f4/0x63f
 [<c11b2d94>] [<c1309bfb>] write_chan+0x11e/0x1e6
 [<c101d6e7>] tcp_in_window+0x2d0/0x4dc
 [<c1030aac>] default_wake_function+0x0/0xc
lock_timer_base+0x20/0x45
 [<c101d6e7>] [<c136357c>] default_wake_function+0x0/0xc
_spin_unlock_irqrestore+0xf/0x23
 [<c11adb1d>] [<c1030b70>] tty_write+0x172/0x21e
__mod_timer+0x9f/0xc6
 [<c11b2c76>] [<f9f8b3da>] write_chan+0x0/0x1e6
 [<c11ad9ab>] tty_write+0x0/0x21e
 [<c1083004>] venet_find_ve+0x1a/0x2a [vznetdev]
vfs_write+0x96/0x176
 [<c1318bd2>] [<c108324c>] sys_write+0x4b/0x11d
ip_nat_fn+0x90/0x224
 [<c1002f4f>] [<c12ecbf2>] syscall_call+0x7/0xb
tcp_check_req+0xfc/0x3ee
 [<c1316429>] ipt_do_table+0x271/0x32e
 [<c12e995d>] tcp_v4_hnd_req+0x48/0x2bb
 [<c12e9db7>] tcp_v4_do_rcv+0x103/0x138
 [<c12a780b>] __skb_checksum_complete+0x19/0x5c
 [<c12ea736>] tcp_v4_rcv+0x94a/0xb5b
 [<c12cc52d>] ip_local_deliver_finish+0x0/0x235
 [<c12cc35d>] ip_local_deliver+0xff/0x2cf
 [<c12cc52d>] ip_local_deliver_finish+0x0/0x235
 [<c12cc9c5>] ip_rcv+0x263/0x5a9
 [<c12ccd0b>] ip_rcv_finish+0x0/0x2fd
 [<c12a411e>] __alloc_skb+0x66/0x136
 [<c12aac3e>] netif_receive_skb+0x268/0x335
 [<c1363513>] _spin_unlock+0xd/0x21
 [<c12aad8e>] process_backlog+0x83/0x109
 [<c12aae83>] net_rx_action+0x6f/0x177
 [<c102c647>] __do_softirq+0xa0/0x151
 [<c1005898>] do_softirq+0x83/0xd6
 =======================
 [<c13611f0>] schedule+0x62c/0xa37
 [<c102c751>] irq_exit+0x59/0x77
 [<c10056d3>] do_IRQ+0x97/0x133
 [<c1000d3e>] default_idle+0x0/0x4f
 [<c100398a>] common_interrupt+0x1a/0x20
 [<c1000d3e>] default_idle+0x0/0x4f
 [<c1000d6a>] default_idle+0x2c/0x4f
 [<c1000ded>] cpu_idle+0x4c/0x9f
 [<c14918c2>] start_kernel+0x1d7/0x227
 [<c1491297>] unknown_bootoption+0x0/0x1d7
BUG: using smp_processor_id() in preemptible [00000001] code: syslog-ng/8833
caller is __call_console_drivers+0x2e/0x64
 [<c1167caf>] debug_smp_processor_id+0x97/0xa8
 [<c1026870>] __call_console_drivers+0x2e/0x64
 [<c1026999>] call_console_drivers+0x74/0x108
 [<c1027369>] do_release_console_sem+0x39/0x7a
 [<c10273c2>] release_console_sem+0x18/0x51
 [<c11b12a3>] opost_block+0x10b/0x110
 [<c11b2d94>] write_chan+0x11e/0x1e6
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c11adb1d>] tty_write+0x172/0x21e
 [<c11b2c76>] write_chan+0x0/0x1e6
 [<c11ad9ab>] tty_write+0x0/0x21e
 [<c1083004>] vfs_write+0x96/0x176
 [<c108324c>] sys_write+0x4b/0x11d
 [<c1002f4f>] syscall_call+0x7/0xb
BUG: using smp_processor_id() in preemptible [00000001] code: syslog-ng/8833
caller is __call_console_drivers+0x2e/0x64
 [<c1167caf>] debug_smp_processor_id+0x97/0xa8
 [<c1026870>] __call_console_drivers+0x2e/0x64
 [<c1026999>] call_console_drivers+0x74/0x108
 [<c1027369>] do_release_console_sem+0x39/0x7a
 [<c10273c2>] release_console_sem+0x18/0x51
 [<c11b12a3>] opost_block+0x10b/0x110
 [<c11b2d94>] write_chan+0x11e/0x1e6
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c11adb1d>] tty_write+0x172/0x21e
 [<c11b2c76>] write_chan+0x0/0x1e6
 [<c11ad9ab>] tty_write+0x0/0x21e
 [<c1083004>] vfs_write+0x96/0x176
 [<c108324c>] sys_write+0x4b/0x11d
 [<c1002f4f>] syscall_call+0x7/0xb
BUG: using smp_processor_id() in preemptible [00000001] code: syslog-ng/8833
caller is __call_console_drivers+0x2e/0x64
 [<c1167caf>] debug_smp_processor_id+0x97/0xa8
 [<c1026870>] __call_console_drivers+0x2e/0x64
 [<c1026999>] call_console_drivers+0x74/0x108
 [<c1027369>] do_release_console_sem+0x39/0x7a
 [<c10273c2>] release_console_sem+0x18/0x51
 [<c11b12a3>] opost_block+0x10b/0x110
 [<c11b2d94>] write_chan+0x11e/0x1e6
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c11adb1d>] tty_write+0x172/0x21e
 [<c11b2c76>] write_chan+0x0/0x1e6
 [<c11ad9ab>] tty_write+0x0/0x21e
 [<c1083004>] vfs_write+0x96/0x176
 [<c108324c>] sys_write+0x4b/0x11d
 [<c1002f4f>] syscall_call+0x7/0xb
BUG: using smp_processor_id() in preemptible [00000001] code: syslog-ng/8833
caller is __call_console_drivers+0x2e/0x64
 [<c1167caf>] debug_smp_processor_id+0x97/0xa8
 [<c1026870>] __call_console_drivers+0x2e/0x64
 [<c1026999>] call_console_drivers+0x74/0x108
 [<c1027369>] do_release_console_sem+0x39/0x7a
 [<c10273c2>] release_console_sem+0x18/0x51
 [<c11b12a3>] opost_block+0x10b/0x110
 [<c11b2d94>] write_chan+0x11e/0x1e6
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c11adb1d>] tty_write+0x172/0x21e
 [<c11b2c76>] write_chan+0x0/0x1e6
 [<c11ad9ab>] tty_write+0x0/0x21e
 [<c1083004>] vfs_write+0x96/0x176
 [<c108324c>] sys_write+0x4b/0x11d
 [<c1002f4f>] syscall_call+0x7/0xb
BUG: using smp_processor_id() in preemptible [00000001] code: syslog-ng/8833
caller is __call_console_drivers+0x2e/0x64
 [<c1167caf>] debug_smp_processor_id+0x97/0xa8
 [<c1026870>] __call_console_drivers+0x2e/0x64
 [<c1026999>] call_console_drivers+0x74/0x108
 [<c1027369>] do_release_console_sem+0x39/0x7a
 [<c10273c2>] release_console_sem+0x18/0x51
 [<c11b12a3>] opost_block+0x10b/0x110
 [<c11b2d94>] write_chan+0x11e/0x1e6
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c11adb1d>] tty_write+0x172/0x21e
 [<c11b2c76>] write_chan+0x0/0x1e6
 [<c11ad9ab>] tty_write+0x0/0x21e
 [<c1083004>] vfs_write+0x96/0x176
 [<c108324c>] sys_write+0x4b/0x11d
 [<c1002f4f>] syscall_call+0x7/0xb
BUG: using smp_processor_id() in preemptible [00000001] code: syslog-ng/8833
caller is __call_console_drivers+0x2e/0x64
 [<c1167caf>] debug_smp_processor_id+0x97/0xa8
 [<c1026870>] __call_console_drivers+0x2e/0x64
 [<c1026999>] call_console_drivers+0x74/0x108
 [<c1027369>] do_release_console_sem+0x39/0x7a
 [<c10273c2>] release_console_sem+0x18/0x51
 [<c11b12a3>] opost_block+0x10b/0x110
 [<c11b2d94>] write_chan+0x11e/0x1e6
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c11adb1d>] tty_write+0x172/0x21e
 [<c11b2c76>] write_chan+0x0/0x1e6
 [<c11ad9ab>] tty_write+0x0/0x21e
 [<c1083004>] vfs_write+0x96/0x176
 [<c108324c>] sys_write+0x4b/0x11d
 [<c1002f4f>] syscall_call+0x7/0xb
BUG: using smp_processor_id() in preemptible [00000001] code: syslog-ng/8833
caller is __call_console_drivers+0x2e/0x64
 [<c1167caf>] debug_smp_processor_id+0x97/0xa8
 [<c1026870>] __call_console_drivers+0x2e/0x64
 [<c1026999>] call_console_drivers+0x74/0x108
 [<c1027369>] do_release_console_sem+0x39/0x7a
 [<c10273c2>] release_console_sem+0x18/0x51
 [<c11b12a3>] opost_block+0x10b/0x110
 [<c11b2d94>] write_chan+0x11e/0x1e6
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c11adb1d>] tty_write+0x172/0x21e
 [<c11b2c76>] write_chan+0x0/0x1e6
 [<c11ad9ab>] tty_write+0x0/0x21e
 [<c1083004>] vfs_write+0x96/0x176
 [<c108324c>] sys_write+0x4b/0x11d
 [<c1002f4f>] syscall_call+0x7/0xb
BUG: using smp_processor_id() in preemptible [00000001] code: syslog-ng/8833
caller is __call_console_drivers+0x2e/0x64
 [<c1167caf>] debug_smp_processor_id+0x97/0xa8
 [<c1026870>] __call_console_drivers+0x2e/0x64
 [<c1026999>] call_console_drivers+0x74/0x108
 [<c1027369>] do_release_console_sem+0x39/0x7a
 [<c10273c2>] release_console_sem+0x18/0x51
 [<c11b12a3>] opost_block+0x10b/0x110
 [<c11b2d94>] write_chan+0x11e/0x1e6
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c11adb1d>] tty_write+0x172/0x21e
 [<c11b2c76>] write_chan+0x0/0x1e6
 [<c11ad9ab>] tty_write+0x0/0x21e
 [<c1083004>] vfs_write+0x96/0x176
 [<c108324c>] sys_write+0x4b/0x11d
 [<c1002f4f>] syscall_call+0x7/0xb
BUG: using smp_processor_id() in preemptible [00000001] code: syslog-ng/8833
caller is __call_console_drivers+0x2e/0x64
 [<c1167caf>] debug_smp_processor_id+0x97/0xa8
 [<c1026870>] __call_console_drivers+0x2e/0x64
 [<c1026999>] call_console_drivers+0x74/0x108
 [<c1027369>] do_release_console_sem+0x39/0x7a
 [<c10273c2>] release_console_sem+0x18/0x51
 [<c11b12a3>] opost_block+0x10b/0x110
 [<c11b2d94>] write_chan+0x11e/0x1e6
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c101d6e7>] default_wake_function+0x0/0xc
 [<c11adb1d>] tty_write+0x172/0x21e
 [<c11b2c76>] write_chan+0x0/0x1e6
 [<c11ad9ab>] tty_write+0x0/0x21e
 [<c1083004>] vfs_write+0x96/0x176
 [<c108324c>] sys_write+0x4b/0x11d
 [<c1002f4f>] syscall_call+0x7/0xb