FYI, -tip testing found this new lockdep workqueue locking assert 
triggered by the Intel HDA sound driver:

[   30.637612]   alloc kstat_irqs on cpu 0 node 0
[   30.647029] IOAPIC[0]: Set routing entry (2-22 -> 0x71 -> IRQ 22 Mode:1 Active:1)
[   30.654533] HDA Intel 0000:00:1b.0: PCI INT A -> GSI 22 (level, low) -> IRQ 22
[   30.661782] HDA Intel 0000:00:1b.0: setting latency timer to 64
[   30.667801] chipset global capabilities = 0x4401
[   30.701090] codec_mask = 0x4
[   30.701090] hda_intel: codec #2 probed OK
[   30.709090] hda-codec: No codec parser is available
[   30.714396] hda-intel: no codecs initialized
[   30.718689] 
[   30.718689] =============================================
[   30.718689] [ INFO: possible recursive locking detected ]
[   30.718689] 2.6.28-tip #2
[   30.718689] ---------------------------------------------
[   30.718689] events/0/7 is trying to acquire lock:
[   30.718689]  (events){--..}, at: [<ffffffff80281050>] flush_workqueue+0x0/0x90
[   30.718689] 
[   30.718689] but task is already holding lock:
[   30.718689]  (events){--..}, at: [<ffffffff8028076a>] run_workqueue+0x14a/0x240
[   30.718689] 
[   30.718689] other info that might help us debug this:
[   30.718689] 2 locks held by events/0/7:
[   30.718689]  #0:  (events){--..}, at: [<ffffffff8028076a>] run_workqueue+0x14a/0x240
[   30.718689]  #1:  (&wfc.work){--..}, at: [<ffffffff8028076a>] run_workqueue+0x14a/0x240
[   30.718689] 
[   30.718689] stack backtrace:
[   30.718689] Pid: 7, comm: events/0 Not tainted 2.6.28-tip #2
[   30.718689] Call Trace:
[   30.718689]  [<ffffffff80295836>] validate_chain+0xc56/0x1340
[   30.718689]  [<ffffffff802974e6>] __lock_acquire+0x376/0x610
[   30.718689]  [<ffffffff80297819>] lock_acquire+0x99/0xd0
[   30.718689]  [<ffffffff80281050>] ? flush_workqueue+0x0/0x90
[   30.718689]  [<ffffffff80281091>] flush_workqueue+0x41/0x90
[   30.718689]  [<ffffffff80281050>] ? flush_workqueue+0x0/0x90
[   30.718689]  [<ffffffff802810f5>] flush_scheduled_work+0x15/0x20
[   30.718689]  [<ffffffff80c59794>] azx_clear_irq_pending+0x54/0x60
[   30.718689]  [<ffffffff80c599ec>] azx_free+0x10c/0x160
[   30.718689]  [<ffffffff80bae9ad>] ? snd_device_free+0x8d/0x100
[   30.718689]  [<ffffffff80c59a52>] azx_dev_free+0x12/0x20
[   30.718689]  [<ffffffff80bae9a1>] snd_device_free+0x81/0x100
[   30.718689]  [<ffffffff80baea89>] snd_device_free_all+0x69/0xa0
[   30.718689]  [<ffffffff80ba8a70>] snd_card_do_free+0x50/0xd0
[   30.718689]  [<ffffffff80ba9602>] snd_card_free+0xa2/0xc0
[   30.718689]  [<ffffffff8061115f>] ? __delay+0xf/0x20
[   30.718689]  [<ffffffff80edbb6a>] azx_probe+0x38a/0x9f0
[   30.718689]  [<ffffffff80c5a240>] ? azx_send_cmd+0x0/0x130
[   30.718689]  [<ffffffff80c5a370>] ? azx_get_response+0x0/0x210
[   30.718689]  [<ffffffff80c59b70>] ? azx_attach_pcm_stream+0x0/0x1b0
[   30.718689]  [<ffffffff802804d0>] ? do_work_for_cpu+0x0/0x30
[   30.718689]  [<ffffffff80634807>] local_pci_probe+0x17/0x20
[   30.718689]  [<ffffffff802804e8>] do_work_for_cpu+0x18/0x30
[   30.718689]  [<ffffffff802804d0>] ? do_work_for_cpu+0x0/0x30
[   30.718689]  [<ffffffff802807bb>] run_workqueue+0x19b/0x240
[   30.718689]  [<ffffffff8028076a>] ? run_workqueue+0x14a/0x240
[   30.718689]  [<ffffffff802809cf>] worker_thread+0xaf/0x110
[   30.718689]  [<ffffffff80284e20>] ? autoremove_wake_function+0x0/0x40
[   30.718689]  [<ffffffff80280920>] ? worker_thread+0x0/0x110
[   30.718689]  [<ffffffff802848e3>] kthread+0x53/0x80
[   30.718689]  [<ffffffff8022c3aa>] child_rip+0xa/0x20
[   30.718689]  [<ffffffff8022bcbe>] ? restore_args+0x0/0x30
[   30.718689]  [<ffffffff80284890>] ? kthread+0x0/0x80
[   30.718689]  [<ffffffff8022c3a0>] ? child_rip+0x0/0x20
[   30.993230] HDA Intel 0000:00:1b.0: PCI INT A disabled
[   30.998430] initcall alsa_card_azx_init+0x0/0x20 returned 0 after 372964 usecs
[   31.005810] calling  alsa_card_korg1212_init+0x0/0x20 @ 1
[   31.011225] bus: 'pci': add driver korg1212

config attached.

Today is the first time i saw this bug, so i guess the guilty commit is 
one of:

8326e32: Merge branch 'topic/hda-resume-fix' into topic/hda
d4d9cd03: ALSA: hda - Add probe_only option
0ff5551: Merge branch 'fix/hda' into topic/hda
5c0b9be: ALSA: hda - Fix a compile warning when CONFIG_PM=n
32e176c: Sound: hda - Restore PCI configuration space with interrupts off
11cd41b: ALSA: hda - Fix build error with CONFIG_SND_HDA_POWER_SAVE
fee2fba: ALSA: hda - Move power_save option to hda_intel.c
986862b: ALSA: hda - make some functions static
ef1681d: ALSA: hda - Add probe_mask quirk for Medion MD96630
41dda0f: ALSA: azx_probe() cleanup
c4da29c: ALSA: hda - support detecting HD Audio devices with PCI class code
0edb945: ALSA: hda - Fix probe errors on Dell Studio Desktop
6ce4a3b: ALSA: hda - Make codec-probing more robust
33fa35e: ALSA: hda - simplify hda_bus ops callbacks
afecd78c: Merge branch 'topic/fix/hda' into topic/hda
34c2535: ALSA: hda - Remove old codec-probe limitation
176d533: ALSA: hda - Add infrastructure for dynamic stream allocation

	Ingo