netdev - Re: [PATCH] b43: Fix lockdep splat on module unload

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Message-Id: <20130225.154805.1538752246011578467.davem@davemloft.net>
Date:	Mon, 25 Feb 2013 15:48:05 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	Larry.Finger@...inger.net
Cc:	linville@...driver.com, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] b43: Fix lockdep splat on module unload

From: Larry Finger <Larry.Finger@...inger.net>
Date: Mon, 25 Feb 2013 10:09:24 -0600

> On unload, b43 produces a lockdep warning that can be summarized in the
> following way:
> 
>  ======================================================
>  [ INFO: possible circular locking dependency detected ]
>  3.8.0-wl+ #117 Not tainted
>  -------------------------------------------------------
>  modprobe/5557 is trying to acquire lock:
>   ((&wl->firmware_load)){+.+.+.}, at: [<ffffffff81062160>] flush_work+0x0/0x2a0
> 
>  but task is already holding lock:
>   (rtnl_mutex){+.+.+.}, at: [<ffffffff813bd7d2>] rtnl_lock+0x12/0x20
> 
>  which lock already depends on the new lock.
>  [ INFO: possible circular locking dependency detected ]
>  ======================================================
> 
> The full output is available at http://lkml.indiana.edu/hypermail/linux/kernel/1302.3/00060.html.
> To summarize, commit 6b6fa58 added a 'cancel_work_sync(&wl->firmware_load)'
> call in the wrong place.
> 
> The fix is to move the cancel_work_sync() call to b43_bcma_remove() and
> b43_ssb_remove(). Thanks to Johannes Berg and Michael Buesch for help in
> diagnosing the log output.
> 
> Signed-off-by: Larry Finger <Larry.Finger@...inger.net>

Applied.
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