- * \author Bernardo Innocenti <bernie@develer.com>
- */
-
-/*
- * $Log$
- * Revision 1.4 2004/07/30 14:30:27 rasky
- * Resa la sig_signal interrupt safe (con il nuovo scheduler IRQ-safe)
- * Rimossa event_doIntr (ora inutile) e semplificata la logica delle macro con funzioni inline
+ * Signals are very low overhead. Using them exclusively to wait
+ * for multiple asynchronous events results in very simple dispatch
+ * logic with low processor and resource usage.
+ *
+ * The "event" module is a higher-level interface that can optionally
+ * deliver signals to processes. Messages provide even higher-level
+ * IPC services built on signals. Semaphore arbitration is also
+ * implemented using signals.
+ *
+ * In this implementation, each process has a limited set of signal
+ * bits (usually 32) and can wait for multiple signals at the same
+ * time using sig_wait(). Signals can also be polled using sig_check(),
+ * but a process spinning on its signals usually defeats their purpose
+ * of providing a multitasking-friendly infrastructure for event-driven
+ * applications.
+ *
+ * Signals are like flags: they are either active or inactive. After an
+ * external event has delivered a particular signal, it remains raised until
+ * the process acknowledges it using either sig_wait() or sig_check().
+ * Counting signals is not a reliable way to count how many times a
+ * particular event has occurred, because the same signal may be
+ * delivered twice before the process can notice.
+ *
+ * Any execution context, including an interrupt handler, can deliver
+ * a signal to a process using sig_signal(). Multiple independent signals
+ * may be delivered at once with a single invocation of sig_signal(),
+ * although this is rarely useful.