1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/hid/hid-wiimote.h b/drivers/hid/hid-wiimote.h
index 301607da7715..34417021606e 100644
--- a/drivers/hid/hid-wiimote.h
+++ b/drivers/hid/hid-wiimote.h
@@ -195,6 +195,16 @@ static inline void wiimote_cmd_complete(struct wiimote_data *wdata)
         complete(&wdata->state.ready);
 }
 
+/* requires the state.lock spinlock to be held */
+static inline void wiimote_cmd_abort(struct wiimote_data *wdata)
+{
+        /* Abort synchronous request by waking up the sleeping caller. But
+         * reset the state.cmd field to an invalid value so no further event
+         * handlers will work with it. */
+        wdata->state.cmd = WIIPROTO_REQ_MAX;
+        complete(&wdata->state.ready);
+}
+
 static inline int wiimote_cmd_acquire(struct wiimote_data *wdata)
 {
         return mutex_lock_interruptible(&wdata->state.sync) ? -ERESTARTSYS : 0;
@@ -223,11 +233,17 @@ static inline int wiimote_cmd_wait(struct wiimote_data *wdata)
 {
         int ret;
 
+        /* The completion acts as implicit memory barrier so we can safely
+         * assume that state.cmd is set on success/failure and isn't accessed
+         * by any other thread, anymore. */
+
         ret = wait_for_completion_interruptible_timeout(&wdata->state.ready, HZ);
         if (ret < 0)
                 return -ERESTARTSYS;
         else if (ret == 0)
                 return -EIO;
+        else if (wdata->state.cmd != WIIPROTO_REQ_NULL)
+                return -EIO;
         else
                 return 0;
 }
@@ -236,9 +252,12 @@ static inline int wiimote_cmd_wait_noint(struct wiimote_data *wdata)
 {
         unsigned long ret;
 
+        /* no locking needed; see wiimote_cmd_wait() */
         ret = wait_for_completion_timeout(&wdata->state.ready, HZ);
         if (!ret)
                 return -EIO;
+        else if (wdata->state.cmd != WIIPROTO_REQ_NULL)
+                return -EIO;
         else
                 return 0;
 }