X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;f=kern%2Fsignal.c;h=5abd7062679aeacd91f085741c18db31e71d29f8;hb=6591f6879a9cbc255ec2040ee968059b47cc31f5;hp=6194251702a0d4eb3dabb1c67ee5e7d434708b8a;hpb=d79f7d6dbc485204f897c9a5ea1f26936cc23744;p=bertos.git

diff --git a/kern/signal.c b/kern/signal.c
index 61942517..5abd7062 100644
--- a/kern/signal.c
+++ b/kern/signal.c
@@ -43,6 +43,15 @@
  * signals.  POSIX signals are usually executed synchronously, like
  * software interrupts.
  *
+ * 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(),
@@ -58,31 +67,33 @@
  * 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 distinct signals
+ * 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.
  *
+ * \section signal_allocation Signal Allocation
+ *
  * There's no hardcoded mapping of specific events to signal bits.
  * The meaning of a particular signal bit is defined by an agreement
  * between the delivering entity and the receiving process.
- * For instance, a terminal driver may be written to deliver
+ * For instance, a terminal driver may be designed to deliver
  * a signal bit called SIG_INT when it reads the CTRL-C sequence
  * from the keyboard, and a process may react to it by quitting.
  *
- * The SIG_SINGLE bit is reserved for a special purpose (this is
- * more a suggestion than a constraint).  When a process wants
- * wait for a single event on the fly, it needs not allocate a
- * free signal from its pool.  Instead, SIG_SINGLE can be used
- *
- * 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.
- *
- * 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.
- *
+ * \section sig_single SIG_SINGLE
+ *
+ * The SIG_SINGLE bit is reserved as a convenient shortcut in those
+ * simple scenarios where a process needs to wait on just one event
+ * synchronously.  By using SIG_SINGLE, there's no need to allocate
+ * a specific signal from the free pool.  The constraints for safely
+ * accessing SIG_SINGLE are:
+ *  - The process MUST sig_wait() exclusively on SIG_SINGLE
+ *  - SIG_SIGNAL MUST NOT be left pending after use (sig_wait() will reset
+ *	  it automatically)
+ *  - Do not sleep between starting the asynchronous task that will fire
+ *    SIG_SINGLE, and the call to  sig_wait().
+ *  - Do not call system functions that may implicitly sleep, such as
+ *    timer_delayTickes().
  *
  * \version $Id$
  *
@@ -119,7 +130,7 @@ sigmask_t sig_check(sigmask_t sigs)
 
 /**
  * Sleep until any of the signals in \a sigs occurs.
- * \return the signal(s) that have awaked the process.
+ * \return the signal(s) that have awoken the process.
  */
 sigmask_t sig_wait(sigmask_t sigs)
 {
@@ -150,8 +161,8 @@ sigmask_t sig_wait(sigmask_t sigs)
 /**
  * Sleep until any of the signals in \a sigs or \a timeout ticks elapse.
  * If the timeout elapse a SIG_TIMEOUT is added to the received signal(s).
- * \return the signal(s) that have awaked the process.
- * \note Caller must check return value to check which signal has awaked the process.
+ * \return the signal(s) that have awoken the process.
+ * \note Caller must check return value to check which signal awoke the process.
  */
 sigmask_t sig_waitTimeout(sigmask_t sigs, ticks_t timeout)
 {
@@ -161,8 +172,8 @@ sigmask_t sig_waitTimeout(sigmask_t sigs, ticks_t timeout)
 
 	ASSERT(!sig_check(SIG_TIMEOUT));
 	ASSERT(!(sigs & SIG_TIMEOUT));
- 	/* IRQ are needed to run timer */
-	ASSERT(IRQ_ENABLED);
+	/* IRQ are needed to run timer */
+	ASSERT(IRQ_ENABLED());
 
 	timer_set_event_signal(&t, proc_current(), SIG_TIMEOUT);
 	timer_setDelay(&t, timeout);
@@ -174,12 +185,13 @@ sigmask_t sig_waitTimeout(sigmask_t sigs, ticks_t timeout)
 	if (!(res & SIG_TIMEOUT) && !sig_check(SIG_TIMEOUT))
 		timer_abort(&t);
 	IRQ_RESTORE(flags);
+	return res;
 }
 
 
 /**
  * Send the signals \a sigs to the process \a proc.
- * The process will be awaken if it was waiting for any of them.
+ * The process will be awoken if it was waiting for any of them.
  *
  * \note This call is interrupt safe.
  */
@@ -191,7 +203,7 @@ void sig_signal(Process *proc, sigmask_t sigs)
 	/* Set the signals */
 	proc->sig_recv |= sigs;
 
-	/* Check if process needs to be awaken */
+	/* Check if process needs to be awoken */
 	if (proc->sig_recv & proc->sig_wait)
 	{
 		/* Wake up process and enqueue in ready list */