一、线程池实现原理
1. 管理者线程
（1）计算线程不够用
- 创建线程
（2） 空闲线程太多
a. 销毁
- 更新要销毁的线程个数
- 通过条件变量完成的
b. 如果空闲太多，任务不够
- 线程阻塞在该条件变量上
c. 发送信号
- pthread_cond_signal
2. 线程池中的线程
（1）从任务队列中取数据
- 任务队列任务
- 执行任务
（2）销毁空闲的线程
- 让线程执行pthread_exit
- 阻塞空闲的线程收到信号：
解除阻塞
只有一个往下执行
在执行任务之前做了销毁操作 -- 自行退出
二、线程池代码实现
1. 初始化一些线程
2. 需要有一个管理者线程
a. 如果使用率超过一定的百分比
创建线程： 按照一定的步长增长
b. 空闲的线程增多
销毁线程
留下的比实际多一些
3. 线程工作的时候
处理数据的时候：
- 互斥锁
- 条件变量
注意：
a. 线程阻塞条件：
任务对列如果为空 cond_empty
pthread_cond_wait(&cond_empty, &mutex);
b. 任务队列中有数据：
激活阻塞在条件变量上的线程： pthread_cond_signal(&cond_empty); pthead_cond_broadcast(&cond_empty);
最终代码：
1 #include <stdlib.h> 2 #include <pthread.h> 3 #include <unistd.h> 4 #include <assert.h> 5 #include <stdio.h> 6 #include <string.h> 7 #include <signal.h> 8 #include <errno.h> 9 #include "threadpool.h" 10 11 #define DEFAULT_TIME 10 /*10s检测一次*/ 12 #define MIN_WAIT_TASK_NUM 10 /*如果queue_size > MIN_WAIT_TASK_NUM 添加新的线程到线程池*/ 13 #define DEFAULT_THREAD_VARY 10 /*每次创建和销毁线程的个数*/ 14 #define true 1 15 #define false 0 16 17 typedef struct { 18 void *(*function)(void *); /* 函数指针，回调函数 */ 19 void *arg; /* 上面函数的参数 */ 20 } threadpool_task_t; /* 各子线程任务结构体 */ 21 22 /* 描述线程池相关信息 */ 23 struct threadpool_t { 24 pthread_mutex_t lock; /* 用于锁住本结构体 */ 25 pthread_mutex_t thread_counter; /* 记录忙状态线程个数de琐 -- busy_thr_num */ 26 pthread_cond_t queue_not_full; /* 当任务队列满时，添加任务的线程阻塞，等待此条件变量 */ 27 pthread_cond_t queue_not_empty; /* 任务队列里不为空时，通知等待任务的线程 */ 28 29 pthread_t *threads; /* 存放线程池中每个线程的tid。数组 */ 30 pthread_t adjust_tid; /* 存管理线程tid */ 31 threadpool_task_t *task_queue; /* 任务队列 */ 32 33 int min_thr_num; /* 线程池最小线程数 */ 34 int max_thr_num; /* 线程池最大线程数 */ 35 int live_thr_num; /* 当前存活线程个数 */ 36 int busy_thr_num; /* 忙状态线程个数 */ 37 int wait_exit_thr_num; /* 要销毁的线程个数 */ 38 39 int queue_front; /* task_queue队头下标 */ 40 int queue_rear; /* task_queue队尾下标 */ 41 int queue_size; /* task_queue队中实际任务数 */ 42 int queue_max_size; /* task_queue队列可容纳任务数上限 */ 43 44 int shutdown; /* 标志位，线程池使用状态，true或false */ 45 }; 46 47 /** 48 * @function void *threadpool_thread(void *threadpool) 49 * @desc the worker thread 50 * @param threadpool the pool which own the thread 51 */ 52 void *threadpool_thread(void *threadpool); 53 54 /** 55 * @function void *adjust_thread(void *threadpool); 56 * @desc manager thread 57 * @param threadpool the threadpool 58 */ 59 void *adjust_thread(void *threadpool); 60 61 /** 62 * check a thread is alive 63 */ 64 int is_thread_alive(pthread_t tid); 65 int threadpool_free(threadpool_t *pool); 66 67 threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size) 68 { 69 int i; 70 threadpool_t *pool = NULL; 71 do { 72 if((pool = (threadpool_t *)malloc(sizeof(threadpool_t))) == NULL) { 73 printf("malloc threadpool fail"); 74 break;/*跳出do while*/ 75 } 76 77 pool->min_thr_num = min_thr_num; 78 pool->max_thr_num = max_thr_num; 79 pool->busy_thr_num = 0; 80 pool->live_thr_num = min_thr_num; /* 活着的线程数 初值=最小线程数 */ 81 pool->queue_size = 0; /* 有0个产品 */ 82 pool->queue_max_size = queue_max_size; 83 pool->queue_front = 0; 84 pool->queue_rear = 0; 85 pool->shutdown = false; /* 不关闭线程池 */ 86 87 /* 根据最大线程上限数， 给工作线程数组开辟空间, 并清零 */ 88 pool->threads = (pthread_t *)malloc(sizeof(pthread_t)*max_thr_num); 89 if (pool->threads == NULL) { 90 printf("malloc threads fail"); 91 break; 92 } 93 memset(pool->threads, 0, sizeof(pthread_t)*max_thr_num); 94 95 /* 队列开辟空间 */ 96 pool->task_queue = (threadpool_task_t *)malloc(sizeof(threadpool_task_t)*queue_max_size); 97 if (pool->task_queue == NULL) { 98 printf("malloc task_queue fail"); 99 break; 100 } 101 102 /* 初始化互斥琐、条件变量 */ 103 if (pthread_mutex_init(&(pool->lock), NULL) != 0 104 || pthread_mutex_init(&(pool->thread_counter), NULL) != 0 105 || pthread_cond_init(&(pool->queue_not_empty), NULL) != 0 106 || pthread_cond_init(&(pool->queue_not_full), NULL) != 0) 107 { 108 printf("init the lock or cond fail"); 109 break; 110 } 111 112 /* 启动 min_thr_num 个 work thread */ 113 for (i = 0; i < min_thr_num; i++) { 114 pthread_create(&(pool->threads[i]), NULL, threadpool_thread, (void *)pool);/*pool指向当前线程池*/ 115 printf("start thread 0x%x... ", (unsigned int)pool->threads[i]); 116 } 117 pthread_create(&(pool->adjust_tid), NULL, adjust_thread, (void *)pool);/* 启动管理者线程 */ 118 119 return pool; 120 121 } while (0); 122 123 threadpool_free(pool); /* 前面代码调用失败时，释放poll存储空间 */ 124 125 return NULL; 126 } 127 128 /* 向线程池中 添加一个任务 */ 129 int threadpool_add(threadpool_t *pool, void*(*function)(void *arg), void *arg) 130 { 131 pthread_mutex_lock(&(pool->lock)); 132 133 /* ==为真，队列已经满， 调wait阻塞 */ 134 while ((pool->queue_size == pool->queue_max_size) && (!pool->shutdown)) { 135 pthread_cond_wait(&(pool->queue_not_full), &(pool->lock)); 136 } 137 if (pool->shutdown) { 138 pthread_mutex_unlock(&(pool->lock)); 139 } 140 141 /* 清空 工作线程 调用的回调函数 的参数arg */ 142 if (pool->task_queue[pool->queue_rear].arg != NULL) { 143 free(pool->task_queue[pool->queue_rear].arg); 144 pool->task_queue[pool->queue_rear].arg = NULL; 145 } 146 /*添加任务到任务队列里*/ 147 pool->task_queue[pool->queue_rear].function = function; 148 pool->task_queue[pool->queue_rear].arg = arg; 149 pool->queue_rear = (pool->queue_rear + 1) % pool->queue_max_size; /* 队尾指针移动, 模拟环形 */ 150 pool->queue_size++; 151 152 /*添加完任务后，队列不为空，唤醒线程池中 等待处理任务的线程*/ 153 pthread_cond_signal(&(pool->queue_not_empty)); 154 pthread_mutex_unlock(&(pool->lock)); 155 156 return 0; 157 } 158 159 /* 线程池中各个工作线程 */ 160 void *threadpool_thread(void *threadpool) 161 { 162 threadpool_t *pool = (threadpool_t *)threadpool; 163 threadpool_task_t task; 164 165 while (true) { 166 /* Lock must be taken to wait on conditional variable */ 167 /*刚创建出线程，等待任务队列里有任务，否则阻塞等待任务队列里有任务后再唤醒接收任务*/ 168 pthread_mutex_lock(&(pool->lock)); 169 170 /*queue_size == 0 说明没有任务，调 wait 阻塞在条件变量上, 若有任务，跳过该while*/ 171 while ((pool->queue_size == 0) && (!pool->shutdown)) { 172 printf("thread 0x%x is waiting ", (unsigned int)pthread_self()); 173 pthread_cond_wait(&(pool->queue_not_empty), &(pool->lock)); 174 175 /*清除指定数目的空闲线程，如果要结束的线程个数大于0，结束线程*/ 176 if (pool->wait_exit_thr_num > 0) { 177 pool->wait_exit_thr_num--; 178 179 /*如果线程池里线程个数大于最小值时可以结束当前线程*/ 180 if (pool->live_thr_num > pool->min_thr_num) { 181 printf("thread 0x%x is exiting ", (unsigned int)pthread_self()); 182 pool->live_thr_num--; 183 pthread_mutex_unlock(&(pool->lock)); 184 pthread_exit(NULL); 185 } 186 } 187 } 188 189 /*如果指定了true，要关闭线程池里的每个线程，自行退出处理*/ 190 if (pool->shutdown) { 191 pthread_mutex_unlock(&(pool->lock)); 192 printf("thread 0x%x is exiting ", (unsigned int)pthread_self()); 193 pthread_exit(NULL); /* 线程自行结束 */ 194 } 195 196 /*从任务队列里获取任务, 是一个出队操作*/ 197 task.function = pool->task_queue[pool->queue_front].function; 198 task.arg = pool->task_queue[pool->queue_front].arg; 199 200 pool->queue_front = (pool->queue_front + 1) % pool->queue_max_size; /* 出队，模拟环形队列 */ 201 pool->queue_size--; 202 203 /*通知可以有新的任务添加进来*/ 204 pthread_cond_broadcast(&(pool->queue_not_full)); 205 206 /*任务取出后，立即将 线程池琐 释放*/ 207 pthread_mutex_unlock(&(pool->lock)); 208 209 /*执行任务*/ 210 printf("thread 0x%x start working ", (unsigned int)pthread_self()); 211 pthread_mutex_lock(&(pool->thread_counter)); /*忙状态线程数变量琐*/ 212 pool->busy_thr_num++; /*忙状态线程数+1*/ 213 pthread_mutex_unlock(&(pool->thread_counter)); 214 (*(task.function))(task.arg); /*执行回调函数任务*/ 215 //task.function(task.arg); /*执行回调函数任务*/ 216 217 /*任务结束处理*/ 218 printf("thread 0x%x end working ", (unsigned int)pthread_self()); 219 pthread_mutex_lock(&(pool->thread_counter)); 220 pool->busy_thr_num--; /*处理掉一个任务，忙状态数线程数-1*/ 221 pthread_mutex_unlock(&(pool->thread_counter)); 222 } 223 224 pthread_exit(NULL); 225 } 226 227 /* 管理线程 */ 228 void *adjust_thread(void *threadpool) 229 { 230 int i; 231 threadpool_t *pool = (threadpool_t *)threadpool; 232 while (!pool->shutdown) { 233 234 sleep(DEFAULT_TIME); /*定时 对线程池管理*/ 235 236 pthread_mutex_lock(&(pool->lock)); 237 int queue_size = pool->queue_size; /* 关注 任务数 */ 238 int live_thr_num = pool->live_thr_num; /* 存活 线程数 */ 239 pthread_mutex_unlock(&(pool->lock)); 240 241 pthread_mutex_lock(&(pool->thread_counter)); 242 int busy_thr_num = pool->busy_thr_num; /* 忙着的线程数 */ 243 pthread_mutex_unlock(&(pool->thread_counter)); 244 245 /* 创建新线程 算法： 任务数大于最小线程池个数, 且存活的线程数少于最大线程个数时 如：30>=10 && 40<100*/ 246 if (queue_size >= MIN_WAIT_TASK_NUM && live_thr_num < pool->max_thr_num) { 247 pthread_mutex_lock(&(pool->lock)); 248 int add = 0; 249 250 /*一次增加 DEFAULT_THREAD 个线程*/ 251 for (i = 0; i < pool->max_thr_num && add < DEFAULT_THREAD_VARY 252 && pool->live_thr_num < pool->max_thr_num; i++) { 253 if (pool->threads[i] == 0 || !is_thread_alive(pool->threads[i])) { 254 pthread_create(&(pool->threads[i]), NULL, threadpool_thread, (void *)pool); 255 add++; 256 pool->live_thr_num++; 257 } 258 } 259 260 pthread_mutex_unlock(&(pool->lock)); 261 } 262 263 /* 销毁多余的空闲线程 算法：忙线程X2 小于 存活的线程数 且 存活的线程数 大于 最小线程数时*/ 264 if ((busy_thr_num * 2) < live_thr_num && live_thr_num > pool->min_thr_num) { 265 266 /* 一次销毁DEFAULT_THREAD个线程, 隨機10個即可 */ 267 pthread_mutex_lock(&(pool->lock)); 268 pool->wait_exit_thr_num = DEFAULT_THREAD_VARY; /* 要销毁的线程数 设置为10 */ 269 pthread_mutex_unlock(&(pool->lock)); 270 271 for (i = 0; i < DEFAULT_THREAD_VARY; i++) { 272 /* 通知处在空闲状态的线程, 他们会自行终止*/ 273 pthread_cond_signal(&(pool->queue_not_empty)); 274 } 275 } 276 } 277 278 return NULL; 279 } 280 281 int threadpool_destroy(threadpool_t *pool) 282 { 283 int i; 284 if (pool == NULL) { 285 return -1; 286 } 287 pool->shutdown = true; 288 289 /*先销毁管理线程*/ 290 pthread_join(pool->adjust_tid, NULL); 291 292 for (i = 0; i < pool->live_thr_num; i++) { 293 /*通知所有的空闲线程*/ 294 pthread_cond_broadcast(&(pool->queue_not_empty)); 295 } 296 for (i = 0; i < pool->live_thr_num; i++) { 297 pthread_join(pool->threads[i], NULL); 298 } 299 threadpool_free(pool); 300 301 return 0; 302 } 303 304 int threadpool_free(threadpool_t *pool) 305 { 306 if (pool == NULL) { 307 return -1; 308 } 309 310 if (pool->task_queue) { 311 free(pool->task_queue); 312 } 313 if (pool->threads) { 314 free(pool->threads); 315 pthread_mutex_lock(&(pool->lock)); 316 pthread_mutex_destroy(&(pool->lock)); 317 pthread_mutex_lock(&(pool->thread_counter)); 318 pthread_mutex_destroy(&(pool->thread_counter)); 319 pthread_cond_destroy(&(pool->queue_not_empty)); 320 pthread_cond_destroy(&(pool->queue_not_full)); 321 } 322 free(pool); 323 pool = NULL; 324 325 return 0; 326 } 327 328 int threadpool_all_threadnum(threadpool_t *pool) 329 { 330 int all_threadnum = -1; 331 pthread_mutex_lock(&(pool->lock)); 332 all_threadnum = pool->live_thr_num; 333 pthread_mutex_unlock(&(pool->lock)); 334 return all_threadnum; 335 } 336 337 int threadpool_busy_threadnum(threadpool_t *pool) 338 { 339 int busy_threadnum = -1; 340 pthread_mutex_lock(&(pool->thread_counter)); 341 busy_threadnum = pool->busy_thr_num; 342 pthread_mutex_unlock(&(pool->thread_counter)); 343 return busy_threadnum; 344 } 345 346 int is_thread_alive(pthread_t tid) 347 { 348 int kill_rc = pthread_kill(tid, 0); //发0号信号，测试线程是否存活 349 if (kill_rc == ESRCH) { 350 return false; 351 } 352 353 return true; 354 } 355 356 /*测试*/ 357 358 #if 1 359 /* 线程池中的线程，模拟处理业务 */ 360 void *process(void *arg) 361 { 362 printf("thread 0x%x working on task %d ",(unsigned int)pthread_self(),*(int *)arg); 363 sleep(1); 364 printf("task %d is end ",*(int *)arg); 365 366 return NULL; 367 } 368 int main(void) 369 { 370 /*threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size);*/ 371 372 threadpool_t *thp = threadpool_create(3,100,100);/*创建线程池，池里最小3个线程，最大100，队列最大100*/ 373 printf("pool inited"); 374 375 //int *num = (int *)malloc(sizeof(int)*20); 376 int num[20], i; 377 for (i = 0; i < 20; i++) { 378 num[i]=i; 379 printf("add task %d ",i); 380 threadpool_add(thp, process, (void*)&num[i]); /* 向线程池中添加任务 */ 381 } 382 sleep(10); /* 等子线程完成任务 */ 383 threadpool_destroy(thp); 384 385 return 0; 386 } 387 388 #endif
1 #ifndef __THREADPOOL_H_ 2 #define __THREADPOOL_H_ 3 4 typedef struct threadpool_t threadpool_t; 5 6 /** 7 * @function threadpool_create 8 * @descCreates a threadpool_t object. 9 * @param thr_num thread num 10 * @param max_thr_num max thread size 11 * @param queue_max_size size of the queue. 12 * @return a newly created thread pool or NULL 13 */ 14 threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size); 15 16 /** 17 * @function threadpool_add 18 * @desc add a new task in the queue of a thread pool 19 * @param pool Thread pool to which add the task. 20 * @param function Pointer to the function that will perform the task. 21 * @param argument Argument to be passed to the function. 22 * @return 0 if all goes well,else -1 23 */ 24 int threadpool_add(threadpool_t *pool, void*(*function)(void *arg), void *arg); 25 26 /** 27 * @function threadpool_destroy 28 * @desc Stops and destroys a thread pool. 29 * @param pool Thread pool to destroy. 30 * @return 0 if destory success else -1 31 */ 32 int threadpool_destroy(threadpool_t *pool); 33 34 /** 35 * @desc get the thread num 36 * @pool pool threadpool 37 * @return # of the thread 38 */ 39 int threadpool_all_threadnum(threadpool_t *pool); 40 41 /** 42 * desc get the busy thread num 43 * @param pool threadpool 44 * return # of the busy thread 45 */ 46 int threadpool_busy_threadnum(threadpool_t *pool); 47 48 #endif
1 src = $(wildcard *.c) 2 targets = $(patsubst %.c, %, $(src)) 3 4 CC = gcc 5 CFLAGS = -lpthread -Wall -g 6 7 all:$(targets) 8 9 $(targets):%:%.c 10 $(CC) $< -o $@ $(CFLAGS) 11 12 .PHONY:clean all 13 clean: 14 -rm -rf $(targets)