QNX Neutrino实时操作系统中多线程同步的实现

在QNX Neutrino实时操作系统中，多线程同步是一项常见的任务。本示例展示了在QNX Neutrino环境下，使用互斥锁和条件变量实现多线程同步的方法。

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define NUM_THREADS 2
int counter = 0;
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; // 互斥锁
pthread_cond_t cond = PTHREAD_COND_INITIALIZER; // 条件变量

void *thread_func(void *threadid) {
    long tid;
    tid = (long) threadid;
    printf("Thread %ld starting...\n", tid);

    pthread_mutex_lock(&mutex);  // 加锁

    while(counter % NUM_THREADS != tid - 1) {  // 检查条件
        pthread_cond_wait(&cond, &mutex);  // 阻塞等待
    }
    counter++;
    printf("Thread %ld: counter = %d\n", tid, counter);

    pthread_cond_broadcast(&cond);  // 唤醒所有线程

    pthread_mutex_unlock(&mutex);  // 解锁
    sleep(rand() % 2); // 增加随机性

    printf("Thread %ld exiting...\n", tid);
    pthread_exit(NULL);
}

int main(void) {
    pthread_t threads[NUM_THREADS];
    int rc;
    long t;

    for (t = 1; t <= NUM_THREADS; t++) {
        printf("Main: creating thread %ld\n", t);
        rc = pthread_create(&threads[t-1], NULL, thread_func, (void *) t);
        if (rc) {
            printf("ERROR; return code from pthread_create() is %d\n", rc);
            exit(-1);
        }
    }

    for (t = 0; t < NUM_THREADS; t++) {
        pthread_join(threads[t], NULL);
    }

    pthread_mutex_destroy(&mutex);  // 释放互斥锁
    pthread_cond_destroy(&cond);  // 释放条件变量
    pthread_exit(NULL);
}

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