Bluetooth: bnep: Fix deadlock in session deletion

Commit f4d7cd4a4c introduced the usage of kthread API.
kthread_stop is a blocking function which returns only when
the thread exits. In this case, the thread can't exit because it's
waiting for the write lock, which is being held by bnep_del_connection()
which is waiting for the thread to exit -- deadlock.

Use atomic_t/wake_up_process instead to signal to the thread to exit.

Signed-off-by: Jaikumar Ganesh <jaikumar@google.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>

2 files changed, 6 insertions, 4 deletions

diff --git a/net/bluetooth/bnep/bnep.h b/net/bluetooth/bnep/bnep.h
index 8e6c06158f8e..e7ee5314f39a 100644
--- a/net/bluetooth/bnep/bnep.h
+++ b/net/bluetooth/bnep/bnep.h
@@ -155,6 +155,7 @@ struct bnep_session {
         unsigned int  role;
         unsigned long state;
         unsigned long flags;
+        atomic_t      terminate;
         struct task_struct *task;
 
         struct ethhdr eh;
diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c
index 7e8ff3c24942..d9edfe8bf9d6 100644
--- a/net/bluetooth/bnep/core.c
+++ b/net/bluetooth/bnep/core.c
@@ -487,7 +487,7 @@ static int bnep_session(void *arg)
         while (1) {
                 set_current_state(TASK_INTERRUPTIBLE);
 
-                if (kthread_should_stop())
+                if (atomic_read(&s->terminate))
                         break;
                 /* RX */
                 while ((skb = skb_dequeue(&sk->sk_receive_queue))) {
@@ -642,9 +642,10 @@ int bnep_del_connection(struct bnep_conndel_req *req)
         down_read(&bnep_session_sem);
 
         s = __bnep_get_session(req->dst);
-        if (s)
-                kthread_stop(s->task);
-        else
+        if (s) {
+                atomic_inc(&s->terminate);
+                wake_up_process(s->task);
+        } else
                 err = -ENOENT;
 
         up_read(&bnep_session_sem);