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

[Kamal Mostafa]

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

    b43: Fix lockdep splat

to the linux-3.8.y-queue branch of the 3.8.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-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.18.

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

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 2fdb3039ac862727cb3f83861835c6d1c09d6007 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: Kamal Mostafa <kamal 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 911c4c0..bb421be 100644
--- a/drivers/net/wireless/b43/main.c
+++ b/drivers/net/wireless/b43/main.c
@@ -2415,6 +2415,7 @@ 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)
 {
@@ -2466,6 +2467,10 @@ 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:
@@ -4630,9 +4635,6 @@ 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. */
@@ -4775,9 +4777,6 @@ 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;

@@ -5438,6 +5437,9 @@ 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);
@@ -5515,6 +5517,9 @@ 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