[PATCH 3.9-stable] Bluetooth: btmrvl: fix thread stopping race

[Jonghwan Choi]

This patch looks like it should be in the 3.9-stable tree, should we apply
it?

------------------

From: "Daniel Drake <dsd@xxxxxxxxxx>"

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@xxxxxxxxxx>
Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
Signed-off-by: John W. Linville <linville@xxxxxxxxxxxxx>
Signed-off-by: Jonghwan Choi <jhbird.choi@xxxxxxxxxxx>
---
 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 3a4343b..9a9f518 100644
--- a/drivers/bluetooth/btmrvl_main.c
+++ b/drivers/bluetooth/btmrvl_main.c
@@ -498,6 +498,10 @@ 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) &&
@@ -513,11 +517,6 @@ 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;
-- 
1.7.9.5

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