linux-kernel - Re: lockdep info message

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Message-ID: <508A8DF9.4080607@broadcom.com>
Date:	Fri, 26 Oct 2012 15:19:53 +0200
From:	"Arend van Spriel" <arend@...adcom.com>
To:	"Peter Zijlstra" <peterz@...radead.org>
cc:	"Ingo Molnar" <mingo@...hat.com>, "Tejun Heo" <tj@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: lockdep info message

On 10/26/2012 01:25 PM, Peter Zijlstra wrote:
> On Fri, 2012-10-26 at 12:15 +0200, Arend van Spriel wrote:
>> Hi Peter and/or Ingo,
>>
>> I am working on a driver (brcmfmac) and when unloading it or unplugging
>> the device I get this info message (see below) upon calling
>> cancel_work_sync(). Just wondering if there is something I need to do in
>> the driver or should it be done in workqueue code.
>
> Your driver, as that's the one allocating the struct work_struct thingy.
>
> You've either failed to use INIT_WORK() or need to use
> INIT_WORK_ONSTACK() if that's appropriate. It looks like you could have
> used DECLARE*_WORK inside a function or something similar.
>
> Anyway, without the driver code present I can't really say much more.
>

I assume INIT_WORK_ONSTACK() can only be used when scheduling process 
waits for the work to complete. The work_struct is located inside a 
driver structure that is allocated upon device probe.

struct brcmf_fweh_info {
	struct work_struct event_work;
};

and it is initialized in that context using:

	INIT_WORK(&fweh->event_work, brcmf_fweh_event_worker);

and used in another context:

	schedule_work(&fweh->event_work);

When cleaning up I do:

	cancel_work_sync(&fweh->event_work);

I can also submit the patch with the entire code as RFC if you do not 
object digging through a couple of hundred lines.

Gr. AvS

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