fix a bug in cmsis-os v1.02 implement

osal/cmsis_os/cmsis_os.c

@@ -122,6 +122,17 @@ osStatus osThreadSetPriority(osThreadId thread_id, osPriority priority)
     return errno_knl2cmsis(tos_task_prio_change((k_task_t *)thread_id, priority_cmsis2knl(priority)));
 }
 
+/**
+ * @brief Pass control to next thread that is in state READY.
+ * @return status code that indicates the execution status of the function.
+ */
+osStatus osThreadYield(void)
+{
+    tos_task_yield();
+    
+    return osOK;
+}
+
 /**
  * @brief Get current priority of an active thread.
  * @param[in]   thread_id   thread ID obtained by \ref osThreadCreate or \ref osThreadGetId.