sema.c
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/*
* Copyright (C) 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 Christian Mehlis <mehlis@inf.fu-berlin.de>
* @author Martine Lenders <mlenders@inf.fu-berlin.de>
* @author René Kijewski <kijewski@inf.fu-berlin.de>
*/
#include <assert.h>
#include <errno.h>
#include <limits.h>
#include "irq.h"
#include "msg.h"
#include "xtimer.h"
#include "sema.h"
#define ENABLE_DEBUG (0)
#include "debug.h"
#define MSG_SIGNAL (0x0501)
#define MSG_TIMEOUT (0x0502)
#define MSG_DESTROYED (0x0503)
int sema_create(sema_t *sema, unsigned int value)
{
if (sema == NULL) {
return -EINVAL;
}
sema->value = value;
/* waiters for the mutex */
sema->queue.first = NULL;
return 0;
}
int sema_destroy(sema_t *sema)
{
unsigned int old_state;
priority_queue_node_t *next;
if (sema == NULL) {
return -EINVAL;
}
old_state = irq_disable();
while ((next = priority_queue_remove_head(&sema->queue)) != NULL) {
msg_t msg;
kernel_pid_t pid = (kernel_pid_t)next->data;
msg.type = MSG_DESTROYED;
msg.content.ptr = sema;
msg_send_int(&msg, pid);
}
irq_restore(old_state);
return 0;
}
int sema_wait_timed_msg(sema_t *sema, uint64_t timeout, msg_t *msg)
{
unsigned old_state;
msg_t timeout_msg;
xtimer_t timeout_timer;
if (sema == NULL) {
return -EINVAL;
}
if (timeout != 0) {
old_state = irq_disable();
timeout_timer.target = 0, timeout_timer.long_target = 0;
timeout_msg.type = MSG_TIMEOUT;
timeout_msg.content.ptr = sema;
/* we will stay in the same stack context so we can use timeout_msg */
xtimer_set_msg64(&timeout_timer, timeout, &timeout_msg, sched_active_pid);
irq_restore(old_state);
}
while (1) {
priority_queue_node_t n;
unsigned value;
old_state = irq_disable();
value = sema->value;
if (value != 0) {
sema->value = value - 1;
irq_restore(old_state);
return 0;
}
/* I'm going blocked */
n.priority = (uint32_t)sched_active_thread->priority;
n.data = (unsigned int)sched_active_pid;
n.next = NULL;
priority_queue_add(&sema->queue, &n);
DEBUG("sema_wait: %" PRIkernel_pid ": Adding node to semaphore queue: prio: %" PRIu32 "\n",
sched_active_thread->pid, sched_active_thread->priority);
irq_restore(old_state);
msg_receive(msg);
old_state = irq_disable();
if (timeout != 0) {
xtimer_remove(&timeout_timer);
}
priority_queue_remove(&sema->queue, &n);
irq_restore(old_state);
if (msg->content.ptr != sema) {
return -EAGAIN;
}
switch (msg->type) {
case MSG_SIGNAL:
continue;
case MSG_TIMEOUT:
return -ETIMEDOUT;
case MSG_DESTROYED:
return -ECANCELED;
default:
return -EAGAIN;
}
}
}
int sema_wait_timed(sema_t *sema, uint64_t timeout)
{
int result;
do {
msg_t msg;
result = sema_wait_timed_msg(sema, timeout, &msg);
DEBUG("sema_wait: %" PRIkernel_pid ": Discarding message from %" PRIkernel_pid "\n",
sched_active_thread->pid, msg->sender_pid);
} while (result == -EAGAIN);
return result;
}
int sema_post(sema_t *sema)
{
unsigned int old_state, value;
priority_queue_node_t *next;
if (sema == NULL) {
return -EINVAL;
}
old_state = irq_disable();
value = sema->value;
if (value == UINT_MAX) {
irq_restore(old_state);
return -EOVERFLOW;
}
++sema->value;
next = priority_queue_remove_head(&sema->queue);
if (next) {
uint16_t prio = (uint16_t)next->priority;
kernel_pid_t pid = (kernel_pid_t) next->data;
msg_t msg;
DEBUG("sema_post: %" PRIkernel_pid ": waking up %" PRIkernel_pid "\n",
sched_active_thread->pid, next_process->pid);
msg.type = MSG_SIGNAL;
msg.content.ptr = sema;
msg_send_int(&msg, pid);
irq_restore(old_state);
sched_switch(prio);
}
else {
irq_restore(old_state);
}
return 0;
}
/** @} */