Re: 2.6.21-mm1 hwsusp: BUG at workqueue.c:106

[Jarek Poplawski <jarkao2@o2.pl>]

On 08-05-2007 12:55, Oleg Nesterov wrote:
> On 05/08, Andrew Morton wrote:
>> On Tue, 08 May 2007 10:57:35 +0200 Jiri Slaby <jirislaby@gmail.com> wrote:
>>
>>> this occured in dmesg during resuming from hwsusp in 2.6.21-mm1 (captured
>>> through netconsole). Perfectly reproducible, it simply happens each time I
>>> try it.
>> Let's cc Oleg.
>>
>>> usb_endpoint usbdev5.1_ep00: PM: resume from 0, parent usb5 still 2
>>> ------------[ cut here ]------------
>>> kernel BUG at /home/l/latest/xxx/kernel/workqueue.c:106!
>>> invalid opcode: 0000 [#1]
>>> SMP
>>> Modules linked in: ipv6 floppy ohci1394 ieee1394 parport_pc parport usbhid
>>> ehci_hcd pata_acpi ff_memless sr_mod cdrom
...
> queue_delayed_work().
> 
> Probably, cancel_delayed_work(&delayed_work->work) was called with the ->timer
> pending. This is wrong, cancel_delayed_work() clears _PENDING unconditionally,

Maybe I miss your point, but clearing is conditional: on timer delete...

I think more suspicious is calling cancel_work_sync() for a delayed work
(with timer pending). Or maybe some race profits from _PENDING cleared
without locking?

BTW, it seems some debugging is needed to show, whose work is doing the
mess.

Regards,
Jarek P.