sema.c
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/*
* Copyright (C) 2016 TriaGnoSys GmbH
* 2013-15 Freie Universität Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @{
*
* @file
*
* @author Víctor Ariño <victor.arino@zii.aero>
*/
#include <errno.h>
#include "irq.h"
#include "assert.h"
#include "sema.h"
#include "xtimer.h"
#define ENABLE_DEBUG (0)
#include "debug.h"
void sema_create(sema_t *sema, unsigned int value)
{
assert(sema != NULL);
sema->value = value;
sema->state = SEMA_OK;
mutex_init(&sema->mutex);
if (value == 0) {
mutex_lock(&sema->mutex);
}
}
void sema_destroy(sema_t *sema)
{
assert(sema != NULL);
sema->state = SEMA_DESTROY;
mutex_unlock(&sema->mutex);
}
int _sema_wait(sema_t *sema, int block, uint64_t us)
{
assert(sema != NULL);
if (sema->state != SEMA_OK) {
return -ECANCELED;
}
int did_block = block;
unsigned old = irq_disable();
while ((sema->value == 0) && block) {
irq_restore(old);
if (us == 0) {
mutex_lock(&sema->mutex);
}
else {
uint64_t start = xtimer_now_usec64();
block = !xtimer_mutex_lock_timeout(&sema->mutex, us);
uint64_t elapsed = xtimer_now_usec64() - start;
if (elapsed < us) {
us -= elapsed;
}
else {
block = 0;
}
}
if (sema->state != SEMA_OK) {
mutex_unlock(&sema->mutex);
return -ECANCELED;
}
old = irq_disable();
}
if (sema->value == 0) {
irq_restore(old);
return (did_block) ? -ETIMEDOUT : -EAGAIN;
}
unsigned int value = --sema->value;
irq_restore(old);
/* only unlock mutex if it was a blocking operation */
if (did_block && value > 0) {
mutex_unlock(&sema->mutex);
}
return 0;
}
int sema_post(sema_t *sema)
{
assert(sema != NULL);
unsigned old = irq_disable();
if (sema->value == UINT_MAX) {
irq_restore(old);
return -EOVERFLOW;
}
unsigned value = sema->value++;
irq_restore(old);
if (value == 0) {
mutex_unlock(&sema->mutex);
}
return 0;
}
/** @} */