- * @param t Thread representing the current context
- * @param ctxt Context to switch to
- * @return Does not return, unless we return to Thread t's context. See
+ * @param ctxt System context variable to which to save the current context.
+ * @param t Thread to which we will swap. Must hold a valid user context.
+ * @return Does not return, unless we return to the system context (ctxt). See