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

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Message-ID: <20070508121232.GE1772@ff.dom.local>
Date:	Tue, 8 May 2007 14:12:33 +0200
From:	Jarek Poplawski <jarkao2@...pl>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Slaby <jirislaby@...il.com>,
	"Rafael J\. Wysocki" <rjw@...k.pl>, Pavel Machek <pavel@....cz>,
	linux-pm@...ts.linux-foundation.org,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.21-mm1 hwsusp: BUG at workqueue.c:106

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@...il.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.
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