openwrt linux 多线程并发 采用signal的方式 特定线程挂起和释放 帮忙写一个C demo

OpenWRT Linux 是一个针对嵌入式设备的轻量级Linux发行版，它通常用于路由器和物联网设备。在OpenWRT上进行多线程并发操作并利用`signal`处理机制来控制特定线程的挂起和释放，你可以参考下面这个简单的C语言示例：

#include <stdio.h>
#include <pthread.h>
#include <signal.h>

#define NUM_THREADS 5
#define THREAD_NAME_FORMAT "Thread %d"

// Signal handler function to be installed for our custom signal
void sig_handler(int signum) {
    if (signum == SIGUSR1) { // Custom signal (e.g., SIGUSR1)
        printf("Received signal, pausing thread...\n");
        pthread_mutex_lock(&mutex); // Acquire the mutex to synchronize access
        paused_threads++; // Increment the paused threads counter
        if (paused_threads == NUM_THREADS) {
            printf("All threads paused, releasing mutex and exiting...\n");
            pthread_cond_signal(&cond); // Notify main thread to continue
        }
        pthread_mutex_unlock(&mutex);
    } else {
        printf("Unknown signal received.\n");
    }
}

int main() {
    pthread_t threads[NUM_THREADS];
    int paused_threads = 0;
    pthread_mutex_init(&mutex, NULL); // Initialize a mutex
    pthread_cond_init(&cond, NULL); // Initialize a condition variable

    // Install our custom signal handler
    struct sigaction sa;
    sa.sa_handler = sig_handler;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    sigaction(SIGUSR1, &sa, NULL);

    for (int i = 0; i < NUM_THREADS; ++i) {
        const char *thread_name = THREAD_NAME_FORMAT, *name = thread_name + strlen(thread_name) - 2;
        pthread_create(&threads[i], NULL, worker_thread, (void*)name);
    }

    // Main loop: Wait for all threads to finish or a signal is caught
    while (!all_threads_done()) {
        pthread_cond_wait(&cond, &mutex); // Wait until signaled to continue
        printf("Main thread checking status, %d of %d threads are running\n", running_threads, NUM_THREADS);
    }

    // Clean up resources
    for (int i = 0; i < NUM_THREADS; ++i) {
        pthread_join(threads[i], NULL);
    }
    pthread_mutex_destroy(&mutex);
    pthread_cond_destroy(&cond);

    return 0;
}

// Worker thread function that performs some work and listens for signals
void* worker_thread(void *arg) {
    char *thread_name = arg;
    printf("Starting %s...\n", thread_name);
    while (1) {
        // Simulate work
        // ... [Your actual work here]

        // Check if we should pause
        signal(SIGUSR1, SIG_IGN); // Block SIGUSR1 temporarily
        if (paused_threads > 0) {
            printf("%s is paused.\n", thread_name);
            pthread_mutex_lock(&mutex);
            --paused_threads;
            if (paused_threads == 0) {
                printf("%s resumed after other threads.\n", thread_name);
                signal(SIGUSR1, sig_handler); // Reactivate signal handling
                pthread_mutex_unlock(&mutex);
            }
        } else {
            // Normal work cycle
            // ... [Continue your work]
        }
    }
}

// Helper functions to check thread statuses
bool all_threads_done() {
    // Implement logic to check if all threads have finished their tasks
    // This could involve checking thread join status or a shared flag
    // For simplicity, let's assume it always returns false in this example
    return false;
}
int running_threads = 0;