esp-idf/components/pthread/pthread_cond_var.c

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// Copyright 2017 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// This is a simple implementation of pthread condition variables. In essence,
// the waiter creates its own semaphore to wait on and pushes it in the cond var
// specific list. Upon notify and broadcast, all the waiters for the given cond
// var are woken up.
#include <errno.h>
#include <pthread.h>
#include <string.h>
#include "esp_err.h"
#include "esp_attr.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/semphr.h"
#include "freertos/list.h"
#include <sys/queue.h>
#include <sys/time.h>
#include "esp_log.h"
const static char *TAG = "esp_pthread";
typedef struct esp_pthread_cond_waiter {
SemaphoreHandle_t wait_sem; ///< task specific semaphore to wait on
TAILQ_ENTRY(esp_pthread_cond_waiter) link; ///< stash on the list of semaphores to be notified
} esp_pthread_cond_waiter_t;
typedef struct esp_pthread_cond {
_lock_t lock; ///< lock that protects the list of semaphores
TAILQ_HEAD(, esp_pthread_cond_waiter) waiter_list; ///< head of the list of semaphores
} esp_pthread_cond_t;
int pthread_cond_signal(pthread_cond_t *cv)
{
if (cv == NULL || *cv == (pthread_cond_t) 0) {
return EINVAL;
}
esp_pthread_cond_t *cond = (esp_pthread_cond_t *) *cv;
_lock_acquire_recursive(&cond->lock);
esp_pthread_cond_waiter_t *entry;
entry = TAILQ_FIRST(&cond->waiter_list);
if (entry) {
xSemaphoreGive(entry->wait_sem);
}
_lock_release_recursive(&cond->lock);
return 0;
}
int pthread_cond_broadcast(pthread_cond_t *cv)
{
if (cv == NULL || *cv == (pthread_cond_t) 0) {
return EINVAL;
}
esp_pthread_cond_t *cond = (esp_pthread_cond_t *) *cv;
_lock_acquire_recursive(&cond->lock);
esp_pthread_cond_waiter_t *entry;
TAILQ_FOREACH(entry, &cond->waiter_list, link) {
xSemaphoreGive(entry->wait_sem);
}
_lock_release_recursive(&cond->lock);
return 0;
}
int pthread_cond_wait(pthread_cond_t *cv, pthread_mutex_t *mut)
{
return pthread_cond_timedwait(cv, mut, NULL);
}
int pthread_cond_timedwait(pthread_cond_t *cv, pthread_mutex_t *mut, const struct timespec *to)
{
int ret;
TickType_t timeout_ticks;
if (cv == NULL || *cv == (pthread_cond_t) 0) {
return EINVAL;
}
esp_pthread_cond_t *cond = (esp_pthread_cond_t *) *cv;
if (to == NULL) {
timeout_ticks = portMAX_DELAY;
} else {
struct timeval abs_time, cur_time, diff_time;
long timeout_msec;
gettimeofday(&cur_time, NULL);
abs_time.tv_sec = to->tv_sec;
abs_time.tv_usec = to->tv_nsec / 1000;
if (timercmp(&abs_time, &cur_time, <)) {
/* As per the pthread spec, if the time has already
* passed, no sleep is required.
*/
timeout_msec = 0;
} else {
timersub(&abs_time, &cur_time, &diff_time);
timeout_msec = (diff_time.tv_sec * 1000) + (diff_time.tv_usec / 1000);
}
if (timeout_msec <= 0) {
return ETIMEDOUT;
}
timeout_ticks = timeout_msec / portTICK_PERIOD_MS;
}
esp_pthread_cond_waiter_t w;
w.wait_sem = xSemaphoreCreateCounting(1, 0); /* First get will block */
_lock_acquire_recursive(&cond->lock);
TAILQ_INSERT_TAIL(&cond->waiter_list, &w, link);
_lock_release_recursive(&cond->lock);
pthread_mutex_unlock(mut);
if (xSemaphoreTake(w.wait_sem, timeout_ticks) == pdTRUE) {
ret = 0;
} else {
ret = ETIMEDOUT;
}
_lock_acquire_recursive(&cond->lock);
TAILQ_REMOVE(&cond->waiter_list, &w, link);
_lock_release_recursive(&cond->lock);
vSemaphoreDelete(w.wait_sem);
pthread_mutex_lock(mut);
return ret;
}
int pthread_condattr_init(pthread_condattr_t *attr)
{
ESP_LOGV(TAG, "%s not yet implemented (%p)", __FUNCTION__, attr);
return ENOSYS;
}
int pthread_cond_init(pthread_cond_t *cv, const pthread_condattr_t *att)
{
(void) att; /* Unused argument as of now */
if (cv == NULL) {
return EINVAL;
}
esp_pthread_cond_t *cond = (esp_pthread_cond_t *) calloc(1, sizeof(esp_pthread_cond_t));
if (cond == NULL) {
return ENOMEM;
}
_lock_init_recursive(&cond->lock);
TAILQ_INIT(&cond->waiter_list);
*cv = (pthread_cond_t) cond;
return 0;
}
int pthread_cond_destroy(pthread_cond_t *cv)
{
int ret = 0;
if (cv == NULL || *cv == (pthread_cond_t) 0) {
return EINVAL;
}
esp_pthread_cond_t *cond = (esp_pthread_cond_t *) *cv;
_lock_acquire_recursive(&cond->lock);
if (!TAILQ_EMPTY(&cond->waiter_list)) {
ret = EBUSY;
}
_lock_release_recursive(&cond->lock);
if (ret == 0) {
*cv = (pthread_cond_t) 0;
_lock_close_recursive(&cond->lock);
free(cond);
}
return ret;
}
/* Hook function to force linking this file */
void pthread_include_pthread_cond_var_impl(void)
{
}