+ * @why is %CLD_STOPPED when about to stop for job control;
+ * we are already in %TASK_STOPPED state, about to call schedule().
+ * It might also be that we have just exited (check %PF_EXITING),
+ * but need to report that a group-wide stop is complete.
+ *
+ * @why is %CLD_CONTINUED when waking up after job control stop and
+ * ready to make a delayed @notify report.
+ *
+ * Return the %CLD_* value for %SIGCHLD, or zero to generate no signal.
+ *
+ * Called with the siglock held.