Bluetooth: Remove unnecessary smp_mb__{before,after}_atomic

The barriers are unneeded; wait_woken() and woken_wake_function()
already provide us with the required synchronization: remove them
and document that we're relying on the (implicit) synchronization
provided by wait_woken() and woken_wake_function().

Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Reviewed-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c
index 7b39658..43c2841 100644 (file)
--- a/net/bluetooth/bnep/core.c
+++ b/net/bluetooth/bnep/core.c
@@ -489,9 +489,6 @@ static int bnep_session(void *arg)
 
        add_wait_queue(sk_sleep(sk), &wait);
        while (1) {
-               /* Ensure session->terminate is updated */
-               smp_mb__before_atomic();
-
                if (atomic_read(&s->terminate))
                        break;
                /* RX */
@@ -512,6 +509,10 @@ static int bnep_session(void *arg)
                                break;
                netif_wake_queue(dev);
 
+               /*
+                * wait_woken() performs the necessary memory barriers
+                * for us; see the header comment for this primitive.
+                */
                wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
        }
        remove_wait_queue(sk_sleep(sk), &wait);

diff --git a/net/bluetooth/cmtp/core.c b/net/bluetooth/cmtp/core.c
index 7f26a5a..07cfa32 100644 (file)
--- a/net/bluetooth/cmtp/core.c
+++ b/net/bluetooth/cmtp/core.c
@@ -288,9 +288,6 @@ static int cmtp_session(void *arg)
 
        add_wait_queue(sk_sleep(sk), &wait);
        while (1) {
-               /* Ensure session->terminate is updated */
-               smp_mb__before_atomic();
-
                if (atomic_read(&session->terminate))
                        break;
                if (sk->sk_state != BT_CONNECTED)
@@ -306,6 +303,10 @@ static int cmtp_session(void *arg)
 
                cmtp_process_transmit(session);
 
+               /*
+                * wait_woken() performs the necessary memory barriers
+                * for us; see the header comment for this primitive.
+                */
                wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
        }
        remove_wait_queue(sk_sleep(sk), &wait);
@@ -431,9 +432,10 @@ int cmtp_del_connection(struct cmtp_conndel_req *req)
                /* Stop session thread */
                atomic_inc(&session->terminate);
 
-               /* Ensure session->terminate is updated */
-               smp_mb__after_atomic();
-
+               /*
+                * See the comment preceding the call to wait_woken()
+                * in cmtp_session().
+                */
                wake_up_interruptible(sk_sleep(session->sock->sk));
        } else
                err = -ENOENT;

diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index 253975c..3734dc1 100644 (file)
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c
@@ -1074,6 +1074,10 @@ static int hidp_session_start_sync(struct hidp_session *session)
 static void hidp_session_terminate(struct hidp_session *session)
 {
        atomic_inc(&session->terminate);
+       /*
+        * See the comment preceding the call to wait_woken()
+        * in hidp_session_run().
+        */
        wake_up_interruptible(&hidp_session_wq);
 }
 
@@ -1193,8 +1197,6 @@ static void hidp_session_run(struct hidp_session *session)
                 *    thread is woken up by ->sk_state_changed().
                 */
 
-               /* Ensure session->terminate is updated */
-               smp_mb__before_atomic();
                if (atomic_read(&session->terminate))
                        break;
 
@@ -1228,14 +1230,15 @@ static void hidp_session_run(struct hidp_session *session)
                hidp_process_transmit(session, &session->ctrl_transmit,
                                      session->ctrl_sock);
 
+               /*
+                * wait_woken() performs the necessary memory barriers
+                * for us; see the header comment for this primitive.
+                */
                wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
        }
        remove_wait_queue(&hidp_session_wq, &wait);
 
        atomic_inc(&session->terminate);
-
-       /* Ensure session->terminate is updated */
-       smp_mb__after_atomic();
 }
 
 static int hidp_session_wake_function(wait_queue_entry_t *wait,