136 lines
4.2 KiB
C
136 lines
4.2 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2002 by Björn Stenberg
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#include "kernel-internal.h"
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#include "semaphore.h"
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/****************************************************************************
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* Simple semaphore functions ;)
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****************************************************************************/
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/* Initialize the semaphore object.
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* max = maximum up count the semaphore may assume (max >= 1)
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* start = initial count of semaphore (0 <= count <= max) */
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void semaphore_init(struct semaphore *s, int max, int start)
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{
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KERNEL_ASSERT(max > 0 && start >= 0 && start <= max,
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"semaphore_init->inv arg\n");
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wait_queue_init(&s->queue);
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s->max = max;
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s->count = start;
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corelock_init(&s->cl);
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}
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/* Down the semaphore's count or wait for 'timeout' ticks for it to go up if
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* it is already 0. 'timeout' as TIMEOUT_NOBLOCK (0) will not block and may
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* safely be used in an ISR. */
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int semaphore_wait(struct semaphore *s, int timeout)
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{
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int ret = OBJ_WAIT_TIMEDOUT;
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int oldlevel = disable_irq_save();
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corelock_lock(&s->cl);
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int count = s->count;
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if(LIKELY(count > 0))
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{
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/* count is not zero; down it */
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s->count = count - 1;
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ret = OBJ_WAIT_SUCCEEDED;
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}
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else if(timeout != 0)
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{
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ASSERT_CPU_MODE(CPU_MODE_THREAD_CONTEXT, oldlevel);
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/* too many waits - block until count is upped... */
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struct thread_entry *current = __running_self_entry();
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block_thread(current, timeout, &s->queue, NULL);
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corelock_unlock(&s->cl);
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/* ...and turn control over to next thread */
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switch_thread();
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/* if explicit wake indicated; do no more */
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if(LIKELY(!wait_queue_ptr(current)))
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return OBJ_WAIT_SUCCEEDED;
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disable_irq();
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corelock_lock(&s->cl);
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/* see if anyone got us after the expired wait */
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if(wait_queue_try_remove(current))
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{
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count = s->count;
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if(count > 0)
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{
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/* down it lately */
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s->count = count - 1;
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ret = OBJ_WAIT_SUCCEEDED;
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}
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}
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}
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/* else just polling it */
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corelock_unlock(&s->cl);
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restore_irq(oldlevel);
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return ret;
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}
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/* Up the semaphore's count and release any thread waiting at the head of the
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* queue. The count is saturated to the value of the 'max' parameter specified
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* in 'semaphore_init'. */
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void semaphore_release(struct semaphore *s)
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{
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unsigned int result = THREAD_NONE;
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int oldlevel = disable_irq_save();
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corelock_lock(&s->cl);
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struct thread_entry *thread = WQ_THREAD_FIRST(&s->queue);
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if(LIKELY(thread != NULL))
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{
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/* a thread was queued - wake it up and keep count at 0 */
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KERNEL_ASSERT(s->count == 0,
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"semaphore_release->threads queued but count=%d!\n", s->count);
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result = wakeup_thread(thread, WAKEUP_DEFAULT);
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}
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else
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{
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int count = s->count;
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if(count < s->max)
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{
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/* nothing waiting - up it */
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s->count = count + 1;
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}
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}
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corelock_unlock(&s->cl);
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restore_irq(oldlevel);
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#if defined(HAVE_PRIORITY_SCHEDULING) && defined(is_thread_context)
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/* No thread switch if not thread context */
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if((result & THREAD_SWITCH) && is_thread_context())
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switch_thread();
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#endif
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(void)result;
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}
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