Warning in kernel/workqueue.c:1225 worker_enter_idle+0xc7/0x120() when HTB shaper is initialized on top of ifb

Hi all.

I tested distro with 3.2.28 kernel on Phenom II 955 at MS-7596 mobo, and I saw
next warning:

------------[ cut here ]------------
WARNING: at
/var/testpoint/LEAF-new/source/i486-unknown-linux-uclibc/linux/linux-3.2.28/kernel/workqueue.c:1225
worker_enter_idle+0xc7/0x120()
Hardware name: MS-7596
Modules linked in: ipv6 k10temp sp5100_tco i2c_piix4 i2c_core
snd_hda_codec_hdmi snd_hda_intel snd_hda_codec snd_pcm snd_timer igb(O) snd
shpchp dca soundcore pci_hotplug snd_page_alloc powernow_k8 freq_table
processor thermal_sys hwmon mperf act_mirred cls_u32 cls_fw sch_ingress
sch_prio sch_sfq sch_htb ifb 8021q softdog pptp gre sha1_generic arc4 ecb
ppp_mppe pppoe pppox ppp_synctty ppp_generic slhc sd_mod pata_atiixp pata_acpi
ahci libahci ata_generic ehci_hcd ohci_hcd libata usbcore scsi_mod usb_common
pcspkr vfat fat isofs
Pid: 325, comm: kworker/1:1 Tainted: G           O 3.2.28-i686 #1
Call Trace:
  [<81032dc8>] ? warn_slowpath_common+0x78/0xb0
  [<810453b7>] ? worker_enter_idle+0xc7/0x120
  [<810453b7>] ? worker_enter_idle+0xc7/0x120
  [<81032e1b>] ? warn_slowpath_null+0x1b/0x20
  [<810453b7>] ? worker_enter_idle+0xc7/0x120
  [<81047417>] ? worker_thread+0x1b7/0x2b0
  [<81047260>] ? manage_workers.isra.31+0x1c0/0x1c0
  [<8104aba9>] ? kthread+0x69/0x70
  [<8104ab40>] ? kthread_worker_fn+0x100/0x100
  [<8127c47e>] ? kernel_thread_helper+0x6/0xd
---[ end trace ac1da733157f3bc5 ]---

It was caused during shaper initialization (creating HTB hierarchical shaper on
ifb0 device, with hash filter table for 3 /22 networks, 3 classes per IP), and
appears only once, at start of shaper init (shaper init takes ~1 minute).
It is reproducible, PID is almost every time the same (just once it was 62xx and
points, as I remember, to kworker/2:1).

Kernel config, script that initializes shaper and script config is in attach.

System has, among other mentioned hardware, 2x2GB DDR3 RAM, and i82576-based
LAN card that uses igb-3.3.6 driver.

Distro is LEAF (http://leaf.sourceforge.net), development branch from git.
Used gcc version is 4.6.3; binutils - 2.21a or 2.22 (I can't remember which one
is actually used for that build - we switched for 2.22 and back to 2.21 after
errors caused by binutils update, then - again to 2.22).

If needed I can place tarball that was used on this PC (~90MB).

I placed this bug at bugzilla (bug 46501), and received recommendation to ask here.