-/*!
+/**
* \file
* <!--
* Copyright 2004 Develer S.r.l. (http://www.develer.com/)
- * Copyright 1999,2000,2001 Bernardo Innocenti <bernie@develer.com>
- * This file is part of DevLib - See devlib/README for information.
+ * Copyright 1999, 2000, 2001 Bernardo Innocenti <bernie@develer.com>
+ * This file is part of DevLib - See README.devlib for information.
* -->
*
* \brief IPC signals implementation.
*
- * Each process can wait for just one signal.
- * Multiple processes can wait for the same signal. In this
- * case, each signal will wake-up one of them.
+ * Signals are a low-level IPC primitive. A process receives a signal
+ * when some external event has happened. Like interrupt requests,
+ * signals do not carry any additional information. If processing a
+ * specific event requires additional data, the process must obtain it
+ * through some other mechanism.
+ *
+ * Despite the name, one shouldn't confuse these signals with POSIX
+ * signals. POSIX signals are usually executed synchronously, like
+ * software interrupts.
+ *
+ * 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 distinct signals
+ * may be delivered at once with a single invocation of sig_signal(),
+ * although this is rarely useful.
+ *
+ * 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
+ * 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.
+ *
*
* \version $Id$
*
* \author Bernardo Innocenti <bernie@develer.com>
*/
-/*
- * $Log$
- * Revision 1.2 2004/06/03 11:27:09 bernie
- * Add dual-license information.
- *
- * Revision 1.1 2004/05/23 17:27:00 bernie
- * Import kern/ subdirectory.
- *
- */
+/*#*
+ *#* $Log$
+ *#* Revision 1.14 2006/07/19 12:56:27 bernie
+ *#* Convert to new Doxygen style.
+ *#*
+ *#* Revision 1.13 2006/02/24 01:17:05 bernie
+ *#* Update for new emulator.
+ *#*
+ *#* Revision 1.12 2005/11/04 16:20:02 bernie
+ *#* Fix reference to README.devlib in header.
+ *#*
+ *#* Revision 1.11 2005/04/11 19:10:28 bernie
+ *#* Include top-level headers from cfg/ subdir.
+ *#*
+ *#* Revision 1.10 2004/12/13 12:07:06 bernie
+ *#* DISABLE_IRQSAVE/ENABLE_IRQRESTORE: Convert to IRQ_SAVE_DISABLE/IRQ_RESTORE.
+ *#*
+ *#* Revision 1.9 2004/12/08 08:57:35 bernie
+ *#* Rename sigset_t to sigmask_t.
+ *#*
+ *#* Revision 1.8 2004/09/14 21:06:44 bernie
+ *#* Use debug.h instead of kdebug.h.
+ *#*
+ *#* Revision 1.7 2004/08/25 14:12:09 rasky
+ *#* Aggiornato il comment block dei log RCS
+ *#*
+ *#* Revision 1.6 2004/08/14 19:37:57 rasky
+ *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
+ *#*
+ *#* Revision 1.5 2004/08/04 21:50:33 bernie
+ *#* Add extensive documentation.
+ *#*
+ *#* 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
+ *#*
+ *#* Revision 1.3 2004/07/30 14:24:16 rasky
+ *#* Task switching con salvataggio perfetto stato di interrupt (SR)
+ *#* Kernel monitor per dump informazioni su stack dei processi
+ *#*
+ *#* Revision 1.2 2004/06/03 11:27:09 bernie
+ *#* Add dual-license information.
+ *#*
+ *#* Revision 1.1 2004/05/23 17:27:00 bernie
+ *#* Import kern/ subdirectory.
+ *#*
+ *#*/
#include "signal.h"
-#include "proc.h"
-#include "proc_p.h"
-#include "hw.h"
-// FIXME
+#include <kern/proc.h>
+#include <kern/proc_p.h>
+#include <cfg/debug.h>
+
#if CONFIG_KERN_SIGNALS
-/*!
+/**
* Check if any of the signals in \a sigs has occurred and clear them.
* Return the signals that have occurred.
*/
-sigset_t sig_check(sigset_t sigs)
+sigmask_t sig_check(sigmask_t sigs)
{
- sigset_t result;
+ sigmask_t result;
+ cpuflags_t flags;
- DISABLE_INTS;
+ IRQ_SAVE_DISABLE(flags);
result = CurrentProcess->sig_recv & sigs;
CurrentProcess->sig_recv &= ~sigs;
- ENABLE_INTS;
+ IRQ_RESTORE(flags);
+
return result;
}
-/*!
+/**
* Sleep until any of the signals in \a sigs occurs.
* Return the signal(s) that have awaked the process.
*/
-sigset_t sig_wait(sigset_t sigs)
+sigmask_t sig_wait(sigmask_t sigs)
{
- sigset_t result;
+ sigmask_t result;
+ cpuflags_t flags;
- DISABLE_INTS;
+ IRQ_SAVE_DISABLE(flags);
- for(;;)
+ /* Loop until we get at least one of the signals */
+ while (!(result = CurrentProcess->sig_recv & sigs))
{
- /* Check if we got at least one of the signals */
- if ((result = CurrentProcess->sig_recv & sigs))
- {
- /* Yes, clear signals and return */
- CurrentProcess->sig_recv &= ~sigs;
- ENABLE_INTS;
- return result;
- }
-
- /* No, go to sleep and proc_schedule() another process */
+ /* go to sleep and proc_schedule() another process */
CurrentProcess->sig_wait = sigs;
proc_schedule();
- }
-}
+ /* When we come back here, a signal must be arrived */
+ ASSERT(!CurrentProcess->sig_wait);
+ ASSERT(CurrentProcess->sig_recv);
+ }
-/*!
- * Send the signals \a sigs to the process \a proc.
- * The process will be awaken if it was waiting for any of them.
- *
- * This call is interrupt safe (no \c DISABLE_INTS/ENABLE_INTS protection)
- */
-void _sig_signal(Process *proc, sigset_t sigs)
-{
- /* Set the signals */
- proc->sig_recv |= sigs;
+ /* Signals found: clear them and return */
+ CurrentProcess->sig_recv &= ~sigs;
- /* Check if process needs to be awaken */
- if (proc->sig_recv & proc->sig_wait)
- {
- /* Wake up process and enqueue in ready list */
- proc->sig_wait = 0;
- SCHED_ENQUEUE(proc);
- }
+ IRQ_RESTORE(flags);
+ return result;
}
-/*!
- * Same as _sig_signal() with interrupt protection.
+/**
+ * Send the signals \a sigs to the process \a proc.
+ * The process will be awaken if it was waiting for any of them.
*
- * \note Inlined manually because some compilers are too
- * stupid to it automatically.
+ * \note This call is interrupt safe.
*/
-void sig_signal(Process *proc, sigset_t sigs)
+void sig_signal(Process *proc, sigmask_t sigs)
{
- DISABLE_INTS;
+ cpuflags_t flags;
+ IRQ_SAVE_DISABLE(flags);
/* Set the signals */
proc->sig_recv |= sigs;
SCHED_ENQUEUE(proc);
}
- ENABLE_INTS;
+ IRQ_RESTORE(flags);
}
#endif /* CONFIG_KERN_SIGNALS */
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