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exp1/task67.c
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272
exp1/task67.c
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/*
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任务7（任选）：编写一个多线程并发应用程序task67.c。
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1）主线程预先创建5个工作线程，然后通过缓冲区发放任务，对等线程从缓冲区提取任务执行，当缓冲区为空时，等待任务。
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2）每个任务内容是以秒为单位的整数等待时间，对等线程取得任务后，调用sleep睡眠指定的秒数，就算任务执行完成。
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3）主线程从终端读取命令，发布任务，命令格式为"<任务数> <秒数>",如输入"10 5"表示创建10个任务，每个任务的运行时间是5秒。
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4）应用程序应支持动态地增加或减少工作线程的数目，一个策略是当缓冲区变满时，将线程数量翻倍，而当缓冲区变为空时，将线程数目减半。
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5）每次工作线程发送变动时，应输出相关信息。
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <pthread.h>
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#include <semaphore.h>
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#define DEFAULT_BUF_SIZE 20
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#define INITIAL_THREADS 5
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#define MAX_THREADS 256
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typedef struct {
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int *buf;
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int n;
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int inpos;
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int outpos;
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sem_t mutex;
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sem_t slots;
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sem_t items;
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} sbuf_t;
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/* 线程池管理 */
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int current_thread_count = INITIAL_THREADS;
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int thread_should_exit[MAX_THREADS];
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pthread_t worker_tids[MAX_THREADS];
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pthread_mutex_t pool_mutex = PTHREAD_MUTEX_INITIALIZER;
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volatile int program_running = 1;
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sbuf_t buf;
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void sbuf_init(sbuf_t *sp, int n)
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{
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sp->buf = (int *)malloc(n * sizeof(int));
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sp->n = n;
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sp->inpos = 0;
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sp->outpos = 0;
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sem_init(&sp->mutex, 0, 1);
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sem_init(&sp->slots, 0, n);
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sem_init(&sp->items, 0, 0);
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}
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void sbuf_deinit(sbuf_t *sp)
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{
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free(sp->buf);
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sem_destroy(&sp->mutex);
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sem_destroy(&sp->slots);
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sem_destroy(&sp->items);
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}
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void sbuf_insert(sbuf_t *sp, int item)
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{
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sem_wait(&sp->slots);
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sem_wait(&sp->mutex);
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sp->buf[sp->inpos] = item;
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sp->inpos = (sp->inpos + 1) % sp->n;
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sem_post(&sp->mutex);
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sem_post(&sp->items);
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}
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int sbuf_remove(sbuf_t *sp)
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{
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sem_wait(&sp->items);
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sem_wait(&sp->mutex);
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int item = sp->buf[sp->outpos];
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sp->outpos = (sp->outpos + 1) % sp->n;
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sem_post(&sp->mutex);
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sem_post(&sp->slots);
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return item;
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}
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int sbuf_is_full(sbuf_t *sp)
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{
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int val;
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sem_getvalue(&sp->slots, &val);
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return val == 0;
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}
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int sbuf_is_empty(sbuf_t *sp)
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{
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int val;
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sem_getvalue(&sp->items, &val);
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return val == 0;
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}
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void *worker(void *arg)
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{
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int my_id = *((int *)arg);
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while (1)
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{
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/* 检查是否应该退出 */
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pthread_mutex_lock(&pool_mutex);
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if (thread_should_exit[my_id])
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{
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pthread_mutex_unlock(&pool_mutex);
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break;
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}
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pthread_mutex_unlock(&pool_mutex);
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int task_seconds = sbuf_remove(&buf);
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/* 再次检查退出标志（可能在等待期间被标记） */
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pthread_mutex_lock(&pool_mutex);
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if (thread_should_exit[my_id])
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{
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pthread_mutex_unlock(&pool_mutex);
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/* 任务还在缓冲区中被取出了，需要重新放回去 */
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sbuf_insert(&buf, task_seconds);
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break;
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}
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pthread_mutex_unlock(&pool_mutex);
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printf("[Worker %d] executing task: sleep %d seconds\n", my_id, task_seconds);
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sleep(task_seconds);
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printf("[Worker %d] task completed\n", my_id);
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}
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printf("[Worker %d] exiting\n", my_id);
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return NULL;
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}
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void adjust_threads_up()
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{
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pthread_mutex_lock(&pool_mutex);
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int new_count = current_thread_count * 2;
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if (new_count > MAX_THREADS) new_count = MAX_THREADS;
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if (new_count <= current_thread_count)
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{
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pthread_mutex_unlock(&pool_mutex);
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return;
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}
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int added = new_count - current_thread_count;
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for (int i = 0; i < added; i++)
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{
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int tid = current_thread_count + i;
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thread_should_exit[tid] = 0;
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int *arg = malloc(sizeof(int));
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*arg = tid;
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pthread_create(&worker_tids[tid], NULL, worker, arg);
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}
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current_thread_count = new_count;
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printf("缓冲区变满，工作线程数翻倍，当前工作线程数为%d个\n", current_thread_count);
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pthread_mutex_unlock(&pool_mutex);
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}
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void adjust_threads_down()
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{
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pthread_mutex_lock(&pool_mutex);
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int new_count = current_thread_count / 2;
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if (new_count < 1) new_count = 1;
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if (new_count >= current_thread_count)
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{
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pthread_mutex_unlock(&pool_mutex);
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return;
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}
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int removed = current_thread_count - new_count;
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/* 标记尾部线程为退出 */
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for (int i = 0; i < removed; i++)
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{
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int tid = current_thread_count - 1 - i;
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thread_should_exit[tid] = 1;
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}
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current_thread_count = new_count;
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printf("缓冲区变空，工作线程数减半，当前工作线程数为%d个\n", current_thread_count);
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/* 插入额外的空槽通知以便标记线程能退出 */
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for (int i = 0; i < removed; i++)
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{
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sbuf_insert(&buf, 0);
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}
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pthread_mutex_unlock(&pool_mutex);
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}
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int main(int argc, char *argv[])
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{
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int buf_size = DEFAULT_BUF_SIZE;
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if (argc >= 2)
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buf_size = atoi(argv[1]);
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printf("Dynamic Thread Pool\n");
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printf("Buffer size: %d, Initial threads: %d\n", buf_size, INITIAL_THREADS);
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printf("Commands: <task_count> <seconds> | 'quit' to exit\n\n");
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sbuf_init(&buf, buf_size);
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/* 创建初始线程 */
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for (int i = 0; i < INITIAL_THREADS; i++)
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{
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thread_should_exit[i] = 0;
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int *arg = malloc(sizeof(int));
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*arg = i;
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pthread_create(&worker_tids[i], NULL, worker, arg);
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}
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/* 主线程命令循环 */
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char line[256];
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while (program_running)
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{
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printf("> ");
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fflush(stdout);
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if (fgets(line, sizeof(line), stdin) == NULL)
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break;
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if (strncmp(line, "quit", 4) == 0)
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break;
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int task_count, task_seconds;
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if (sscanf(line, "%d %d", &task_count, &task_seconds) != 2)
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{
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printf("Invalid command. Usage: <task_count> <seconds>\n");
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continue;
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}
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printf("Adding %d tasks, each %d seconds...\n", task_count, task_seconds);
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for (int i = 0; i < task_count; i++)
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{
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/* 插入前检查是否满 */
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if (sbuf_is_full(&buf))
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{
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adjust_threads_up();
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}
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sbuf_insert(&buf, task_seconds);
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}
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/* 检查插入后是否需要调整 */
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int slots_val, items_val;
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sem_getvalue(&buf.slots, &slots_val);
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sem_getvalue(&buf.items, &items_val);
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printf("Buffer status: %d/%d slots free, %d items pending\n",
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slots_val, buf_size, items_val);
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}
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/* 等待所有任务完成并通知线程退出 */
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printf("\nWaiting for pending tasks to complete...\n");
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while (!sbuf_is_empty(&buf))
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{
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sleep(1);
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}
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/* 标记所有线程退出并唤醒它们 */
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pthread_mutex_lock(&pool_mutex);
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for (int i = 0; i < current_thread_count; i++)
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{
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thread_should_exit[i] = 1;
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}
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/* 插入足够多的信号量以唤醒所有等待的线程 */
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for (int i = 0; i < current_thread_count; i++)
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{
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sbuf_insert(&buf, 0);
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}
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pthread_mutex_unlock(&pool_mutex);
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/* 等待所有线程结束 */
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for (int i = 0; i < current_thread_count; i++)
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{
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pthread_join(worker_tids[i], NULL);
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}
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printf("All workers exited. Program terminating.\n");
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sbuf_deinit(&buf);
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return 0;
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}
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