[ 3.5.y.z extended stable ] Patch "Bluetooth: btmrvl: fix thread stopping race" has been added to staging queue

[Luis Henriques]

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

    Bluetooth: btmrvl: fix thread stopping race

to the linux-3.5.y-queue branch of the 3.5.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-3.5.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 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 95d7da8707b525251cfc5d23fb7cb548da9245a4 Mon Sep 17 00:00:00 2001
From: Daniel Drake <dsd at laptop.org>
Date: Tue, 11 Jun 2013 15:40:20 -0400
Subject: [PATCH] Bluetooth: btmrvl: fix thread stopping race

commit ea05fea9042620ac3b8ab9a3e5e4d2ed80c89244 upstream.

There is currently a race condition in the btmrvl_remove_card() which
is causing hangs on suspend for OLPC. When the race occurs,
kthread_stop() never returns.

The problem is that btmrvl_service_main_thread() calls kthread_should_stop()
and then does a fair number of things before restarting the loop and
sleeping.

If the thread gets stopped after kthread_should_stop() is checked, but
before the sleep happens, the thread will go to sleep and won't necessarily
be woken up.

Move the kthread_should_stop() check into a race-free place.

Signed-off-by: Daniel Drake <dsd at laptop.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan at collabora.co.uk>
Signed-off-by: John W. Linville <linville at tuxdriver.com>
Cc: Jonghwan Choi <jhbird.choi at samsung.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/bluetooth/btmrvl_main.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/bluetooth/btmrvl_main.c b/drivers/bluetooth/btmrvl_main.c
index dc304de..2c63a21 100644
--- a/drivers/bluetooth/btmrvl_main.c
+++ b/drivers/bluetooth/btmrvl_main.c
@@ -496,6 +496,10 @@ static int btmrvl_service_main_thread(void *data)
 		add_wait_queue(&thread->wait_q, &wait);

 		set_current_state(TASK_INTERRUPTIBLE);
+		if (kthread_should_stop()) {
+			BT_DBG("main_thread: break from main thread");
+			break;
+		}

 		if (adapter->wakeup_tries ||
 				((!adapter->int_count) &&
@@ -511,11 +515,6 @@ static int btmrvl_service_main_thread(void *data)

 		BT_DBG("main_thread woke up");

-		if (kthread_should_stop()) {
-			BT_DBG("main_thread: break from main thread");
-			break;
-		}
-
 		spin_lock_irqsave(&priv->driver_lock, flags);
 		if (adapter->int_count) {
 			adapter->int_count = 0;
--
1.8.1.2