[3.11.y.z extended stable] Patch "b43: Fix lockdep splat" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    b43: Fix lockdep splat

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 4d05f16617f2ad9fd04578069820ccda439ba322 Mon Sep 17 00:00:00 2001
From: Larry Finger <Larry.Finger at lwfinger.net>
Date: Sun, 12 Jan 2014 15:11:37 -0600
Subject: b43: Fix lockdep splat

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 at gmail.com>
Tested-by: yury <urykhy at gmail.com>
Signed-off-by: Larry Finger <Larry.Finger at lwfinger.net>
Signed-off-by: John W. Linville <linville at tuxdriver.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/wireless/b43/main.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/b43/main.c b/drivers/net/wireless/b43/main.c
index 0e933bb..bccc6ca 100644
--- 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(struct b43_wldev *dev)
 	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. */
@@ -4781,9 +4783,6 @@ static int b43_wireless_core_init(struct b43_wldev *dev)

 	b43_set_status(dev, B43_STAT_INITIALIZED);

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

@@ -5450,6 +5449,9 @@ static void b43_bcma_remove(struct bcma_device *core)

 	b43_one_core_detach(wldev->dev);

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

 	ieee80211_free_hw(wl->hw);
@@ -5527,6 +5529,9 @@ static void b43_ssb_remove(struct ssb_device *sdev)

 	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.
--
1.8.3.2