[PATCH 3/3] Bluetooth: hidp: fix possible might sleep error in hidp_session_thread

[Jeffy Chen]

It looks like hidp_session_thread has same pattern as the issue reported in
old rfcomm:

        while (1) {
                set_current_state(TASK_INTERRUPTIBLE);
                if (condition)
                        break;
                // may call might_sleep here
                schedule();
        }
        __set_current_state(TASK_RUNNING);

Which fixed at:
        dfb2fae Bluetooth: Fix nested sleeps

So let's fix it at the same way, also follow the suggestion of:
https://lwn.net/Articles/628628/

Signed-off-by: Jeffy Chen <jeffy.c...@rock-chips.com>
---

 net/bluetooth/hidp/core.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index 0bec458..43d6e6a 100644
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c
@@ -36,6 +36,7 @@
 #define VERSION "1.2"
 
 static DECLARE_RWSEM(hidp_session_sem);
+static DECLARE_WAIT_QUEUE_HEAD(hidp_session_wq);
 static LIST_HEAD(hidp_session_list);
 
 static unsigned char hidp_keycode[256] = {
@@ -1068,12 +1069,15 @@ static int hidp_session_start_sync(struct hidp_session 
*session)
  * Wake up session thread and notify it to stop. This is asynchronous and
  * returns immediately. Call this whenever a runtime error occurs and you want
  * the session to stop.
- * Note: wake_up_process() performs any necessary memory-barriers for us.
  */
 static void hidp_session_terminate(struct hidp_session *session)
 {
        atomic_inc(&session->terminate);
-       wake_up_process(session->task);
+
+       /* Ensure session->terminate is updated */
+       smp_mb__after_atomic();
+
+       wake_up_interruptible(&hidp_session_wq);
 }
 
 /*
@@ -1180,7 +1184,9 @@ static void hidp_session_run(struct hidp_session *session)
        struct sock *ctrl_sk = session->ctrl_sock->sk;
        struct sock *intr_sk = session->intr_sock->sk;
        struct sk_buff *skb;
+       DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
+       add_wait_queue(&hidp_session_wq, &wait);
        for (;;) {
                /*
                 * This thread can be woken up two ways:
@@ -1188,12 +1194,10 @@ static void hidp_session_run(struct hidp_session 
*session)
                 *    session->terminate flag and wakes this thread up.
                 *  - Via modifying the socket state of ctrl/intr_sock. This
                 *    thread is woken up by ->sk_state_changed().
-                *
-                * Note: set_current_state() performs any necessary
-                * memory-barriers for us.
                 */
-               set_current_state(TASK_INTERRUPTIBLE);
 
+               /* Ensure session->terminate is updated */
+               smp_mb__before_atomic();
                if (atomic_read(&session->terminate))
                        break;
 
@@ -1227,11 +1231,14 @@ static void hidp_session_run(struct hidp_session 
*session)
                hidp_process_transmit(session, &session->ctrl_transmit,
                                      session->ctrl_sock);
 
-               schedule();
+               wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
        }
+       remove_wait_queue(&hidp_session_wq, &wait);
 
        atomic_inc(&session->terminate);
-       set_current_state(TASK_RUNNING);
+
+       /* Ensure session->terminate is updated */
+       smp_mb__after_atomic();
 }
 
 /*
-- 
2.1.4