-/*!
+/**
* \file
* <!--
- * Copyright 2001,2004 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.
+ * This file is part of BeRTOS.
+ *
+ * Bertos is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * As a special exception, you may use this file as part of a free software
+ * library without restriction. Specifically, if other files instantiate
+ * templates or use macros or inline functions from this file, or you compile
+ * this file and link it with other files to produce an executable, this
+ * file does not by itself cause the resulting executable to be covered by
+ * the GNU General Public License. This exception does not however
+ * invalidate any other reasons why the executable file might be covered by
+ * the GNU General Public License.
+ *
+ * Copyright 2001, 2004 Develer S.r.l. (http://www.develer.com/)
+ * Copyright 1999, 2000, 2001 Bernardo Innocenti <bernie@develer.com>
+ *
* -->
*
* \brief Semaphore based synchronization services.
* \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.
- *
- */
-
#include "sem.h"
-#include "proc.h"
-#include "proc_p.h"
-#include "signal.h"
-#include "hw.h"
+#include <kern/proc.h>
+#include <kern/proc_p.h>
+#include <kern/signal.h>
+#include <cfg/debug.h>
+
+INLINE void sem_verify(struct Semaphore *s)
+{
+ (void)s;
+ ASSERT(s);
+ LIST_ASSERT_VALID(&s->wait_queue);
+ ASSERT(s->nest_count >= 0);
+ ASSERT(s->nest_count < 128); // heuristic max
+}
-/*!
- * \brief Initialize a Semaphore structure
+/**
+ * \brief Initialize a Semaphore structure.
*/
void sem_init(struct Semaphore *s)
{
- INITLIST(&s->wait_queue);
+ LIST_INIT(&s->wait_queue);
s->owner = NULL;
s->nest_count = 0;
}
-/*!
+/**
* \brief Attempt to lock a semaphore without waiting.
*
* \return true in case of success, false if the semaphore
*
* \note each call to sem_attempt() must be matched by a
* call to sem_release().
+ *
+ * \see sem_obtain() sem_release()
*/
bool sem_attempt(struct Semaphore *s)
{
- DISABLE_INTS;
+ bool result = false;
+
+ proc_forbid();
+ sem_verify(s);
if ((!s->owner) || (s->owner == CurrentProcess))
{
s->owner = CurrentProcess;
s->nest_count++;
- ENABLE_INTS;
- return true;
+ result = true;
}
- ENABLE_INTS;
- return false;
+ proc_permit();
+
+ return result;
}
-/*!
+/**
* \brief Lock a semaphore.
*
* If the semaphore is already owned by another process, the caller
* the most common case: the semaphore is free or locked
* by the calling process itself. Rearranging this code
* is probably a bad idea.
+ *
+ * \sa sem_release() sem_attempt()
*/
void sem_obtain(struct Semaphore *s)
{
- DISABLE_INTS;
+ proc_forbid();
+ sem_verify(s);
/* Is the semaphore already locked by another process? */
- if (s->owner && (s->owner != CurrentProcess))
+ if (UNLIKELY(s->owner && (s->owner != CurrentProcess)))
{
/* Append calling process to the wait queue */
ADDTAIL(&s->wait_queue, (Node *)CurrentProcess);
- ENABLE_INTS;
- /* We will awake only when the current owner calls
- * ReleaseSemaphore(). Then, the semaphore will already
+ /*
+ * We will wake up only when the current owner calls
+ * sem_release(). Then, the semaphore will already
* be locked for us.
*/
+ proc_permit();
proc_schedule();
}
else
{
- /* The semaphore is free: lock it */
+ ASSERT(LIST_EMPTY(&s->wait_queue));
+
+ /* The semaphore was free: lock it */
s->owner = CurrentProcess;
s->nest_count++;
- ENABLE_INTS;
+ proc_permit();
}
}
-/*!
- * \brief Releases a lock on a previously locked semaphore.
+/**
+ * \brief Release a lock on a previously locked semaphore.
*
* If the nesting count of the semaphore reaches zero,
* the next process waiting for it will be awaken.
* the most common case: the semaphore has been locked just
* once and nobody else was waiting for it. Rearranging
* this code is probably a bad idea.
+ *
+ * \sa sem_obtain() sem_attempt()
*/
void sem_release(struct Semaphore *s)
{
- DISABLE_INTS;
+ proc_forbid();
+ sem_verify(s);
+
+ ASSERT(s->owner == CurrentProcess);
- /* Decremement nesting count and check if the semaphore
- * has been fully unlocked
+ /*
+ * Decrement nesting count and check if the semaphore
+ * has been fully unlocked.
*/
if (--s->nest_count == 0)
{
+ Process *proc;
+
/* Disown semaphore */
s->owner = NULL;
- /* Anybody still waiting for this semaphore? */
- if (!ISLISTEMPTY(&s->wait_queue))
+ /* Give semaphore to the first applicant, if any */
+ if (UNLIKELY((proc = (Process *)list_remHead(&s->wait_queue))))
{
- /* Give semaphore to the first applicant */
- Process *proc = (Process *)s->wait_queue.head;
- REMOVE((Node *)proc);
s->nest_count = 1;
s->owner = proc;
SCHED_ENQUEUE(proc);
}
}
- ENABLE_INTS;
+ proc_permit();
}
-
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