RIOT/sys/posix/pthread/pthread_cond.c

/*
 * Copyright (C) 2014 Hamburg University of Applied Sciences (HAW)
 *
 * 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.
 */

/**
 * @ingroup     sys
 * @{
 *
 * @file
 * @brief       Condition variable implementation
 *
 * @author      Martin Landsmann <martin.landsmann@haw-hamburg.de>
 * @author      René Kijewski <rene.kijewski@fu-berlin.de>
 *
 * @}
 */
#include <errno.h>

#include "pthread_cond.h"
#include "thread.h"
#include "xtimer.h"
#include "sched.h"
#include "irq.h"
#include "debug.h"

int pthread_cond_condattr_destroy(pthread_condattr_t *attr)
{
    if (attr != NULL) {
        DEBUG("pthread_cond_condattr_destroy: currently attributes are not supported.\n");
    }

    return 0;
}

int pthread_cond_condattr_init(pthread_condattr_t *attr)
{
    if (attr != NULL) {
        DEBUG("pthread_cond_condattr_init: currently attributes are not supported.\n");
    }

    return 0;
}

int pthread_condattr_getpshared(const pthread_condattr_t *attr, int *pshared)
{
    (void)attr;
    (void)pshared;

    return 0;
}

int pthread_condattr_setpshared(pthread_condattr_t *attr, int pshared)
{
    (void)attr;
    (void)pshared;

    return 0;
}

int pthread_condattr_getclock(const pthread_condattr_t *attr, clockid_t *clock_id)
{
    (void)attr;
    (void)clock_id;

    return 0;
}

int pthread_condattr_setclock(pthread_condattr_t *attr, clockid_t clock_id)
{
    (void)attr;
    (void)clock_id;

    return 0;
}

int pthread_cond_init(pthread_cond_t *cond, pthread_condattr_t *attr)
{
    if (attr != NULL) {
        DEBUG("pthread_cond_init: currently attributes are not supported.\n");
    }

    cond->queue.first = NULL;
    return 0;
}

int pthread_cond_destroy(pthread_cond_t *cond)
{
    pthread_cond_init(cond, NULL);
    return 0;
}

void _init_cond_wait(pthread_cond_t *cond, priority_queue_node_t *n)
{
    n->priority = sched_active_thread->priority;
    n->data = sched_active_pid;
    n->next = NULL;

    /* the signaling thread may not hold the mutex, the queue is not thread safe */
    unsigned old_state = irq_disable();
    priority_queue_add(&(cond->queue), n);
    irq_restore(old_state);
}

int pthread_cond_wait(pthread_cond_t *cond, mutex_t *mutex)
{
    if (cond == NULL) {
        return EINVAL;
    }
    priority_queue_node_t n;
    _init_cond_wait(cond, &n);

    mutex_unlock_and_sleep(mutex);

    mutex_lock(mutex);

    return 0;
}

int pthread_cond_timedwait(pthread_cond_t *cond, mutex_t *mutex, const struct timespec *abstime)
{
    if (cond == NULL) {
        return EINVAL;
    }

    uint64_t now = xtimer_now_usec64();
    uint64_t then = ((uint64_t)abstime->tv_sec * US_PER_SEC) +
                    (abstime->tv_nsec / NS_PER_US);

    int ret = 0;
    if (then > now) {
        xtimer_t timer;
        priority_queue_node_t n;

        _init_cond_wait(cond, &n);
        xtimer_set_wakeup64(&timer, (then - now), sched_active_pid);

        mutex_unlock_and_sleep(mutex);

        if (n.data != -1u) {
            /* on signaling n.data is set to -1u */
            /* if it isn't set, then the wakeup is either spurious or a timer wakeup */
            unsigned old_state = irq_disable();
            priority_queue_remove(&(cond->queue), &n);
            irq_restore(old_state);
            ret = ETIMEDOUT;
        }
        xtimer_remove(&timer);
    }
    else {
        mutex_unlock(mutex);
        ret = ETIMEDOUT;
    }
    mutex_lock(mutex);
    return ret;
}

int pthread_cond_signal(pthread_cond_t *cond)
{
    unsigned old_state = irq_disable();

    priority_queue_node_t *head = priority_queue_remove_head(&(cond->queue));
    int other_prio = -1;
    if (head != NULL) {
        thread_t *other_thread = (thread_t *) sched_threads[head->data];
        if (other_thread) {
            other_prio = other_thread->priority;
            sched_set_status(other_thread, STATUS_PENDING);
        }
        head->data = -1u;
    }

    irq_restore(old_state);

    if (other_prio >= 0) {
        sched_switch(other_prio);
    }

    return 0;
}

static int max_prio(int a, int b)
{
    return (a < 0) ? b : ((a < b) ? a : b);
}

int pthread_cond_broadcast(pthread_cond_t *cond)
{
    unsigned old_state = irq_disable();

    int other_prio = -1;

    while (1) {
        priority_queue_node_t *head = priority_queue_remove_head(&(cond->queue));
        if (head == NULL) {
            break;
        }

        thread_t *other_thread = (thread_t *) sched_threads[head->data];
        if (other_thread) {
            other_prio = max_prio(other_prio, other_thread->priority);
            sched_set_status(other_thread, STATUS_PENDING);
        }
        head->data = -1u;
    }

    irq_restore(old_state);

    if (other_prio >= 0) {
        sched_switch(other_prio);
    }

    return 0;
}