base_c, base_cpp: updated documentation of spinlock implementations

base_c/include/embb/base/c/mutex.h

@@ -98,6 +98,9 @@ int embb_mutex_init(
 /**
  * Waits until the mutex can be locked and locks it.
  *
+ * \note This method yields the current thread in regular,
+ *       implementation-defined intervals.
+ *
  * \pre \c mutex is initialized \n
  *      If the mutex type is plain, \c mutex must not be locked by the current
  *      thread.

base_cpp/include/embb/base/mutex.h

@@ -192,6 +192,9 @@ class Spinlock {
   /**
    * Waits until the spinlock can be locked and locks it.
    *
+   * \note This method yields the current thread in regular,
+   *       implementation-defined intervals.
+   *
    * \pre The spinlock is not locked by the current thread.
    * \post The spinlock is locked.
    * \threadsafe