[PATCH 3.13 044/140] b43: Fix lockdep splat

Greg Kroah-Hartman
2014-02-04T21:46:41Z

From: Larry Finger <Larry.Finger@lwfinger.net>

commit 09164043f63c947a49797750a09ca1cd7c31108e upstream.

In https://bugzilla.kernel.org/show_bug.cgi?id=67561, a locking dependency is reported
when b43 is used with hostapd, and rfkill is used to kill the radio output.

The lockdep splat (in part) is as follows:

======================================================
[ INFO: possible circular locking dependency detected ]
3.12.0 #1 Not tainted
-------------------------------------------------------
rfkill/10040 is trying to acquire lock:
(rtnl_mutex){+.+.+.}, at: [<ffffffff8146f282>] rtnl_lock+0x12/0x20

but task is already holding lock:
(rfkill_global_mutex){+.+.+.}, at: [<ffffffffa04832ca>] rfkill_fop_write+0x6a/0x170 [rfkill]

--snip--

Chain exists of:
rtnl_mutex --> misc_mtx --> rfkill_global_mutex

The fix is to move the initialization of the hardware random number generator
outside the code range covered by the rtnl_mutex.

Reported-by: yury <urykhy@gmail.com>
Tested-by: yury <urykhy@gmail.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/wireless/b43/main.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

--- a/drivers/net/wireless/b43/main.c
+++ b/drivers/net/wireless/b43/main.c
@@ -2424,6 +2424,7 @@ error:

static int b43_one_core_attach(struct b43_bus_dev *dev, struct b43_wl *wl);
static void b43_one_core_detach(struct b43_bus_dev *dev);
+static int b43_rng_init(struct b43_wl *wl);

static void b43_request_firmware(struct work_struct *work)
{
@@ -2475,6 +2476,10 @@ start_ieee80211:
goto err_one_core_detach;
wl->hw_registred = true;
b43_leds_register(wl->current_dev);
+
+ /* Register HW RNG driver */
+ b43_rng_init(wl);
+
goto out;

err_one_core_detach:
@@ -4636,9 +4641,6 @@ static void b43_wireless_core_exit(struc
if (!dev || b43_status(dev) != B43_STAT_INITIALIZED)
return;

- /* Unregister HW RNG driver */
- b43_rng_exit(dev->wl);
-
b43_set_status(dev, B43_STAT_UNINIT);

/* Stop the microcode PSM. */
@@ -4795,9 +4797,6 @@ static int b43_wireless_core_init(struct

b43_set_status(dev, B43_STAT_INITIALIZED);

- /* Register HW RNG driver */
- b43_rng_init(dev->wl);
-
out:
return err;

@@ -5464,6 +5463,9 @@ static void b43_bcma_remove(struct bcma_

b43_one_core_detach(wldev->dev);

+ /* Unregister HW RNG driver */
+ b43_rng_exit(wl);
+
b43_leds_unregister(wl);

ieee80211_free_hw(wl->hw);
@@ -5541,6 +5543,9 @@ static void b43_ssb_remove(struct ssb_de

b43_one_core_detach(dev);

+ /* Unregister HW RNG driver */
+ b43_rng_exit(wl);
+
if (list_empty(&wl->devlist)) {
b43_leds_unregister(wl);
/* Last core on the chip unregistered.