I've found one other earlier occurrence:
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Jan 11 16:05:35 azul kernel: [28271.973412] ------------[ cut here ]------------
Jan 11 16:05:35 azul kernel: [28271.973424] WARNING: at /build/buildd/linux-3.7.0/arch/x86/kernel/apic/ipi.c:109 default_send_IPI_mask_logical+0xb2/0xf0()
Jan 11 16:05:35 azul kernel: [28271.973426] Hardware name: 2516CTO
Jan 11 16:05:35 azul kernel: [28271.973431] empty IPI mask
Jan 11 16:05:35 azul kernel: [28271.973434] Modules linked in: veth(F) thinkpad_acpi ch341 usbserial ext2(F) overlayfs(F) ip6table_filter(F) ip6_tables(F) ebtable_nat(F) ebtables(F) xt_state(F) ipt_REJECT(F) xt_CHECKSUM(F) iptable_mangle(F) xt_tcpudp(F) iptable_filter(F) ipt_MASQUERADE(F) iptable_nat(F) nf_conntrack_ipv4(F) nf_defrag_ipv4(F) nf_nat_ipv4(F) nf_nat(F) nf_conntrack(F) ip_tables(F) x_tables(F) bridge(F) stp(F) llc(F) rfcomm bnep parport_pc(F) ppdev(F) deflate(F) zlib_deflate(F) ctr(F) twofish_generic(F) twofish_i586(F) twofish_common(F) camellia_generic(F) serpent_sse2_i586(F) serpent_generic(F) glue_helper(F) blowfish_generic(F) blowfish_common(F) cast5_generic(F) des_generic(F) xcbc(F) rmd160(F) crypto_null(F) af_key(F) xfrm_algo(F) nfsd(F) auth_rpcgss(F) nfs_acl(F) nfs(F) binfmt_misc(F) lockd(F) sunrpc(F) fscache(F) usblp uvcvideo btusb videobuf2_vmalloc videobuf2_memops videobuf2_core nvidia(POF) bluetooth videodev coretemp arc4(F) snd_hda_codec_hdmi kvm_intel kvm iwldvm joydev(F) snd_hda_code
Jan 11 16:05:35 azul kernel: c_conexant snd_hda_intel snd_hda_codec mac80211 snd_hwdep(F) snd_pcm(F) nvram(F) snd_page_alloc(F) snd_seq_midi(F) snd_seq_midi_event(F) snd_rawmidi(F) snd_seq(F) aesni_intel(F) aes_i586(F) snd_seq_device(F) xts(F) iwlwifi psmouse(F) lrw(F) gf128mul(F) snd_timer(F) ablk_helper(F) cryptd(F) snd(F) cfg80211 mei soundcore(F) serio_raw(F) intel_ips dm_multipath(F) mac_hid tpm_tis mxm_wmi lpc_ich scsi_dh wmi microcode(F) video(F) lp(F) parport(F) mmc_block hid_generic usbhid hid firewire_ohci sdhci_pci sdhci firewire_core usb_storage(F) uas e1000e(F) crc_itu_t(F) nbd(F) [last unloaded: thinkpad_acpi]
Jan 11 16:05:35 azul kernel: [28271.973620] Pid: 22003, comm: pool Tainted: PF          O 3.7.0-7-generic #15-Ubuntu
Jan 11 16:05:35 azul kernel: [28271.973623] Call Trace:
Jan 11 16:05:35 azul kernel: [28271.973634]  [<c1049fc2>] warn_slowpath_common+0x72/0xa0
Jan 11 16:05:35 azul kernel: [28271.973640]  [<c1032c62>] ? default_send_IPI_mask_logical+0xb2/0xf0
Jan 11 16:05:35 azul kernel: [28271.973644]  [<c1032c62>] ? default_send_IPI_mask_logical+0xb2/0xf0
Jan 11 16:05:35 azul kernel: [28271.973649]  [<c104a093>] warn_slowpath_fmt+0x33/0x40
Jan 11 16:05:35 azul kernel: [28271.973654]  [<c1032c62>] default_send_IPI_mask_logical+0xb2/0xf0
Jan 11 16:05:35 azul kernel: [28271.973660]  [<c1030cd5>] native_send_call_func_ipi+0x45/0x60
Jan 11 16:05:35 azul kernel: [28271.973666]  [<c10a3cb2>] smp_call_function_many+0x172/0x200
Jan 11 16:05:35 azul kernel: [28271.973672]  [<c10426e0>] ? do_flush_tlb_all+0x50/0x50
Jan 11 16:05:35 azul kernel: [28271.973678]  [<c10427bb>] native_flush_tlb_others+0x2b/0x30
Jan 11 16:05:35 azul kernel: [28271.973683]  [<c1042a60>] flush_tlb_page+0x50/0xa0
Jan 11 16:05:35 azul kernel: [28271.973688]  [<c1041576>] ptep_set_access_flags+0x66/0x80
Jan 11 16:05:35 azul kernel: [28271.973695]  [<c112aeb1>] do_wp_page+0x3d1/0x910
Jan 11 16:05:35 azul kernel: [28271.973703]  [<c107bf3e>] ? try_to_wake_up+0x18e/0x230
Jan 11 16:05:35 azul kernel: [28271.973708]  [<c112d094>] handle_pte_fault+0x234/0x520
Jan 11 16:05:35 azul kernel: [28271.973712]  [<c10439d7>] ? kmap_atomic_prot+0xe7/0x100
Jan 11 16:05:35 azul kernel: [28271.973718]  [<c112e3ad>] handle_mm_fault+0x1ed/0x290
Jan 11 16:05:35 azul kernel: [28271.973725]  [<c15f5e71>] __do_page_fault+0x181/0x4b0
Jan 11 16:05:35 azul kernel: [28271.973731]  [<c109686b>] ? ktime_get_ts+0x4b/0x150
Jan 11 16:05:35 azul kernel: [28271.973737]  [<c10a2cb0>] ? sys_futex+0x80/0x130
Jan 11 16:05:35 azul kernel: [28271.973743]  [<c12e5971>] ? copy_to_user+0x41/0x60
Jan 11 16:05:35 azul kernel: [28271.973747]  [<c15f61a0>] ? __do_page_fault+0x4b0/0x4b0
Jan 11 16:05:35 azul kernel: [28271.973752]  [<c15f61ad>] do_page_fault+0xd/0x10
Jan 11 16:05:35 azul kernel: [28271.973757]  [<c15f3197>] error_code+0x67/0x6c
Jan 11 16:05:35 azul kernel: [28271.973763]  [<c15f0000>] ? nl_portid_hash_rehash+0x13d/0x176
Jan 11 16:05:35 azul kernel: [28271.973766] ---[ end trace 6bd7cd0ea82c8536 ]---
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