pthread: Added support for pthread condition variables

This is required for std::condition_variable support

Signed-off-by: Amey Inamdar <amey.inamdar@gmail.com>
This commit is contained in:
Amey Inamdar 2017-10-12 16:28:19 +05:30 committed by Ivan Grokhotkov
parent 597ce3b800
commit edb2400742
3 changed files with 290 additions and 0 deletions

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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 <rom/queue.h>
#include <sys/time.h>
#define LOG_LOCAL_LEVEL CONFIG_LOG_DEFAULT_LEVEL
#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)
{
ESP_LOGV(TAG, "%s %p", __FUNCTION__, 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)
{
ESP_LOGV(TAG, "%s %p", __FUNCTION__, 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)
{
ESP_LOGV(TAG, "%s %p %p", __FUNCTION__, cv, 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;
ESP_LOGV(TAG, "%s %p %p %p", __FUNCTION__, cv, mut, to);
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 */
ESP_LOGV(TAG, "%s %p %p", __FUNCTION__, cv, att);
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;
ESP_LOGV(TAG, "%s %p", __FUNCTION__, 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);
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;
}

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#include <iostream>
#include <thread>
#include <condition_variable>
#include <chrono>
#include <mutex>
#include <atomic>
#include "unity.h"
#if __GTHREADS && __GTHREADS_CXX0X
std::condition_variable cv;
std::mutex cv_m;
std::atomic<int> i{0};
static void waits(int idx, int timeout_ms)
{
std::unique_lock<std::mutex> lk(cv_m);
auto now = std::chrono::system_clock::now();
if(cv.wait_until(lk, now + std::chrono::milliseconds(timeout_ms), [](){return i == 1;}))
std::cout << "Thread " << idx << " finished waiting. i == " << i << '\n';
else
std::cout << "Thread " << idx << " timed out. i == " << i << '\n';
}
static void signals(int signal_ms)
{
std::this_thread::sleep_for(std::chrono::milliseconds(signal_ms));
std::cout << "Notifying...\n";
cv.notify_all();
std::this_thread::sleep_for(std::chrono::milliseconds(signal_ms));
i = 1;
std::cout << "Notifying again...\n";
cv.notify_all();
}
TEST_CASE("C++ condition_variable", "[std::condition_variable]")
{
i = 0;
std::thread t1(waits, 1, 100), t2(waits, 2, 800), t3(signals, 200);
t1.join();
t2.join();
t3.join();
std::cout << "All threads joined\n";
}
#endif

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#include <iostream>
#include <future>
#include <thread>
#include "unity.h"
#if __GTHREADS && __GTHREADS_CXX0X
TEST_CASE("C++ future", "[std::future]")
{
// future from a packaged_task
std::packaged_task<int()> task([]{ return 7; }); // wrap the function
std::future<int> f1 = task.get_future(); // get a future
std::thread t(std::move(task)); // launch on a thread
// future from an async()
std::future<int> f2 = std::async(std::launch::async, []{ return 8; });
// future from a promise
std::promise<int> p;
std::future<int> f3 = p.get_future();
std::thread( [&p]{ p.set_value_at_thread_exit(9); }).detach();
std::cout << "Waiting..." << std::flush;
f1.wait();
f2.wait();
f3.wait();
std::cout << "Done!\nResults are: "
<< f1.get() << ' ' << f2.get() << ' ' << f3.get() << '\n';
t.join();
}
#endif