linux-kernel - Re: Lockdep splat when unloading b43

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Message-ID: <512A6197.2000908@lwfinger.net>
Date:	Sun, 24 Feb 2013 12:53:11 -0600
From:	Larry Finger <Larry.Finger@...inger.net>
To:	Michael Büsch <m@...s.ch>
CC:	Rafał Miłecki <zajec5@...il.com>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	b43-dev <b43-dev@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Lockdep splat when unloading b43

On 02/24/2013 12:32 PM, Michael Büsch wrote:
> On Sun, 24 Feb 2013 11:31:47 -0600
> Larry Finger <Larry.Finger@...inger.net> wrote:
>
>> With the current wireless-testing tree, unloading b43 produces the lockdep log
>> splat copied below. My understanding of locking is deficient, and I would like
>> to learn. Any help on understanding this problem is appreciated.
>
> A few questions:
> Is there any reason for using the global workqueue and not mac80211's workqueue?

My original thought was that we needed the firmware load queue before mac80211 
was running for b43; however, I now realize that my thinking was wrong.

> Why is the workqueue cancelled in the core_stop callback? Wouldn't it make more
> sense to cancel it in bcma_remove/ssb_remove?

It certainly would.

> This would probably fix the circular dependency. But I'm not entirely sure, because
> I'm not that familiar with the code anymore.

I know that a lot has changed, but your instincts are still good.

Thanks,

Larry



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