Add missing prologue_callback_pop_func and prologue_callback_pop_arg documentation

include/starpu_task.h

@@ -844,7 +844,28 @@ struct starpu_task
 	*/
 	void *prologue_callback_arg;
 
+	/** Optional field, the default value is <c>NULL</c>. This is a
+	   function pointer of prototype <c>void (*f)(void*)</c>
+	   which specifies a possible callback. If this pointer is
+	   non-<c>NULL</c>, the callback function is executed on the host
+	   when the task is pop-ed from the scheduler, just before getting
+	   executed. The callback is passed the value contained in the
+	   starpu_task::prologue_callback_pop_arg field.
+	   No callback is executed if the field is set to <c>NULL</c>.
+
+	   With starpu_task_insert() and alike this can be specified thanks to
+	   ::STARPU_PROLOGUE_CALLBACK_POP followed by the function pointer.
+	*/
 	void (*prologue_callback_pop_func)(void *);
+	/**
+	   Optional field, the default value is <c>NULL</c>. This is
+	   the pointer passed to the prologue_callback_pop function. This
+	   field is ignored if the field
+	   starpu_task::prologue_callback_pop_func is set to <c>NULL</c>.
+
+	   With starpu_task_insert() and alike this can be specified thanks to
+	   ::STARPU_PROLOGUE_CALLBACK_POP_ARG followed by the argument.
+	   */
 	void *prologue_callback_pop_arg;
 
 	/**