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	Mon, 13 Jul 2009 15:50:23 -0400
Subject: Re: [RFC/RFT] rtl8187: Fix for kernel oops when unloading with
 LEDs enabled
From: Johannes Berg <johannes@sipsolutions.net>
To: Larry Finger <Larry.Finger@lwfinger.net>
Cc: John W Linville <linville@tuxdriver.com>,
	linux-wireless@vger.kernel.org
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Date: Mon, 13 Jul 2009 21:49:49 +0200
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On Mon, 2009-07-13 at 14:47 -0500, Larry Finger wrote:
> Johannes Berg wrote:
> > On Mon, 2009-07-13 at 10:43 -0500, Larry Finger wrote:
> >> When rtl8187 is unloaded and CONFIG_RTL8187_LEDS is set, the kernel
> >> may oops when the module is unloaded as the workqueue for led_on was
> >> not being cancelled. To prevent interference between cfg80211 and rtl8=
187,
> >> a separate workqueue has also been established.
> >=20
> > It doesn't seem like a separate workqueue should be necessary -- why is
> > it? Might make more sense to fix cfg80211 or mac80211 instead.
>=20
> Probably.
>=20
> Attached is the dump for the locking error when b43 is unloaded.
>=20
>=20
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D
> [ INFO: possible circular locking dependency detected ]
> 2.6.31-rc2-wl #178
> -------------------------------------------------------
> modprobe/14721 is trying to acquire lock:
>  (&rdev->conn_work){+.+.+.}, at: [<ffffffff810510c0>]
> __cancel_work_timer+0xd9/0x222
>=20
> but task is already holding lock:
>  (cfg80211_mutex){+.+.+.}, at: [<ffffffffa0220524>]
> wiphy_unregister+0x3a/0xf8 [cfg80211]

That's purely a problem within cfg80211, and I don't think it could be
solved by your patch at all. I did send a patch earlier today though to
solve this.

(maybe you didn't reboot, and then lockdep was disabled after the first
warning?)

johannes

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