Bluetooth: cmtp: Fix deadlock in session deletion

Commit fada4ac339 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 cmtp_del_connection()
which is waiting for the thread to exit -- deadlock.

Revert cmtp_reset_ctr to its original behavior: non-blocking signalling
for the session to terminate.

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

3 files changed, 6 insertions, 3 deletions

diff --git a/net/bluetooth/cmtp/capi.c b/net/bluetooth/cmtp/capi.c
index 040f67b1297..50f0d135eb8 100644
--- a/net/bluetooth/cmtp/capi.c
+++ b/net/bluetooth/cmtp/capi.c
@@ -386,7 +386,8 @@ static void cmtp_reset_ctr(struct capi_ctr *ctrl)
 
         capi_ctr_down(ctrl);
 
-        kthread_stop(session->task);
+        atomic_inc(&session->terminate);
+        wake_up_process(session->task);
 }
 
 static void cmtp_register_appl(struct capi_ctr *ctrl, __u16 appl, capi_register_params *rp)
diff --git a/net/bluetooth/cmtp/cmtp.h b/net/bluetooth/cmtp/cmtp.h
index db43b54ac9a..c32638dddbf 100644
--- a/net/bluetooth/cmtp/cmtp.h
+++ b/net/bluetooth/cmtp/cmtp.h
@@ -81,6 +81,7 @@ struct cmtp_session {
 
         char name[BTNAMSIZ];
 
+        atomic_t terminate;
         struct task_struct *task;
 
         wait_queue_head_t wait;
diff --git a/net/bluetooth/cmtp/core.c b/net/bluetooth/cmtp/core.c
index 2eb854ab10f..42cb2f4c0db 100644
--- a/net/bluetooth/cmtp/core.c
+++ b/net/bluetooth/cmtp/core.c
@@ -295,7 +295,7 @@ static int cmtp_session(void *arg)
         while (1) {
                 set_current_state(TASK_INTERRUPTIBLE);
 
-                if (kthread_should_stop())
+                if (atomic_read(&session->terminate))
                         break;
                 if (sk->sk_state != BT_CONNECTED)
                         break;
@@ -416,7 +416,8 @@ int cmtp_del_connection(struct cmtp_conndel_req *req)
                 skb_queue_purge(&session->transmit);
 
                 /* Stop session thread */
-                kthread_stop(session->task);
+                atomic_inc(&session->terminate);
+                wake_up_process(session->task);
         } else
                 err = -ENOENT;