Input: use full RCU API

RT guys alerted me to the fact that in their tree spinlocks
are preemptible and it is better to use full RCU API
(rcu_read_lock()/rcu_read_unlock()) to be safe.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

1 files changed, 15 insertions, 21 deletions

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 3070c7aa1237..2f2b020cd629 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -65,16 +65,16 @@ static int input_defuzz_abs_event(int value, int old_val, int fuzz)
 
 /*
  * Pass event through all open handles. This function is called with
- * dev->event_lock held and interrupts disabled. Because of that we
- * do not need to use rcu_read_lock() here although we are using RCU
- * to access handle list. Note that because of that write-side uses
- * synchronize_sched() instead of synchronize_ru().
+ * dev->event_lock held and interrupts disabled.
  */
 static void input_pass_event(struct input_dev *dev,
                              unsigned int type, unsigned int code, int value)
 {
-        struct input_handle *handle = rcu_dereference(dev->grab);
+        struct input_handle *handle;
+
+        rcu_read_lock();
 
+        handle = rcu_dereference(dev->grab);
         if (handle)
                 handle->handler->event(handle, type, code, value);
         else
@@ -82,6 +82,7 @@ static void input_pass_event(struct input_dev *dev,
                         if (handle->open)
                                 handle->handler->event(handle,
                                                         type, code, value);
+        rcu_read_unlock();
 }
 
 /*
@@ -293,9 +294,11 @@ void input_inject_event(struct input_handle *handle,
         if (is_event_supported(type, dev->evbit, EV_MAX)) {
                 spin_lock_irqsave(&dev->event_lock, flags);
 
+                rcu_read_lock();
                 grab = rcu_dereference(dev->grab);
                 if (!grab || grab == handle)
                         input_handle_event(dev, type, code, value);
+                rcu_read_unlock();
 
                 spin_unlock_irqrestore(&dev->event_lock, flags);
         }
@@ -325,11 +328,7 @@ int input_grab_device(struct input_handle *handle)
         }
 
         rcu_assign_pointer(dev->grab, handle);
-        /*
-         * Not using synchronize_rcu() because read-side is protected
-         * by a spinlock with interrupts off instead of rcu_read_lock().
-         */
-        synchronize_sched();
+        synchronize_rcu();
 
  out:
         mutex_unlock(&dev->mutex);
@@ -344,7 +343,7 @@ static void __input_release_device(struct input_handle *handle)
         if (dev->grab == handle) {
                 rcu_assign_pointer(dev->grab, NULL);
                 /* Make sure input_pass_event() notices that grab is gone */
-                synchronize_sched();
+                synchronize_rcu();
 
                 list_for_each_entry(handle, &dev->h_list, d_node)
                         if (handle->open && handle->handler->start)
@@ -404,7 +403,7 @@ int input_open_device(struct input_handle *handle)
                          * Make sure we are not delivering any more events
                          * through this handle
                          */
-                        synchronize_sched();
+                        synchronize_rcu();
                 }
         }
 
@@ -451,11 +450,11 @@ void input_close_device(struct input_handle *handle)
 
         if (!--handle->open) {
                 /*
-                 * synchronize_sched() makes sure that input_pass_event()
+                 * synchronize_rcu() makes sure that input_pass_event()
                  * completed and that no more input events are delivered
                  * through this handle
                  */
-                synchronize_sched();
+                synchronize_rcu();
         }
 
         mutex_unlock(&dev->mutex);
@@ -1477,12 +1476,7 @@ int input_register_handle(struct input_handle *handle)
                 return error;
         list_add_tail_rcu(&handle->d_node, &dev->h_list);
         mutex_unlock(&dev->mutex);
-        /*
-         * We don't use synchronize_rcu() here because we rely
-         * on dev->event_lock to protect read-side critical
-         * section in input_pass_event().
-         */
-        synchronize_sched();
+        synchronize_rcu();
 
         /*
          * Since we are supposed to be called from ->connect()
@@ -1521,7 +1515,7 @@ void input_unregister_handle(struct input_handle *handle)
         mutex_lock(&dev->mutex);
         list_del_rcu(&handle->d_node);
         mutex_unlock(&dev->mutex);
-        synchronize_sched();
+        synchronize_rcu();
 }
 EXPORT_SYMBOL(input_unregister_handle);