简单线程池
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <pthread.h> #include <assert.h> // 任务结构体，使用队列保存 typedef struct worker_s worker_t; struct worker_s { void *(*process)(void *arg); void *arg; worker_t *next; }; // 线程池结构 typedef struct pool_s pool_t; struct pool_s { pthread_mutex_t mutex; pthread_cond_t cond; worker_t *head; worker_t *tail; pthread_t *ids; int max_thread_num; }; void *thread_cb(void *arg) { pool_t *pool = (pool_t*)arg; long self = pthread_self(); while (1) { int ret; if ((ret = pthread_mutex_lock(&pool->mutex)) != 0) { fprintf(stderr, "pthread_mutex_lock: %d\n", ret); break; } printf("in %ld\n", self); while (pool->head == NULL) { printf("wait %ld\n", self); if ((ret = pthread_cond_wait(&pool->cond, &pool->mutex)) != 0) { fprintf(stderr, "pthread_cond_wait: %d\n", ret); pthread_mutex_unlock(&pool->mutex); } } assert(pool->head != NULL); // 取出队列保存的第一个任务 worker_t *w = pool->head; pool->head = pool->head->next; pthread_mutex_unlock(&pool->mutex); w->process(w->arg); free(w); } return NULL; } pool_t *pool_init(int thread_num) { pool_t *pool = (pool_t*)malloc(sizeof(pool_t)); if (pool) { if (pthread_mutex_init(&pool->mutex, NULL) != 0) { return NULL; } if (pthread_cond_init(&pool->cond, NULL) != 0) { pthread_mutex_destroy(&pool->mutex); return NULL; } pool->head = pool->tail = NULL; pool->max_thread_num = thread_num; pool->ids = (pthread_t*)malloc(sizeof(pthread_t) * thread_num); for (int i = 0; i < thread_num; i++) { pthread_create(&pool->ids[i], NULL, thread_cb, (void*)pool); pthread_detach(pool->ids[i]); } } return pool; } int pool_add_worker(pool_t *pool, void *(*process)(void *arg), void *arg) { worker_t *w = (worker_t*)malloc(sizeof(worker_t)); if (NULL == w) { return -1; } w->process = process; w->arg = arg; w->next = NULL; pthread_mutex_lock(&pool->mutex); if (pool->head != NULL) { pool->tail->next = w; pool->tail = w; } else { pool->head = pool->tail = w; } pthread_cond_signal(&pool->cond);
pthread_mutex_unlock(&pool->mutex); return 0; } void *p_cb(void *arg) { sleep(2); printf("callback func print\n"); return NULL; } int main() { pool_t * pool = pool_init(3); for (int i = 0; i < 5; ++i) { if (pool_add_worker(pool, p_cb, NULL) != 0) { fprintf(stderr, "add worker error\n"); } } getchar(); return 0; }
C++版本的：
#include <atomic> #include <chrono> #include <condition_variable> #include <functional> #include <future> #include <iostream> #include <mutex> #include <queue> #include <thread> #include <vector> class Pool { public: Pool(int n = std::thread::hardware_concurrency()) { for (int i = 0; i < n; ++i) { threads_.emplace_back(&Pool::ThreadCb, this); } } ~Pool() { Stop(); } // 添加任务 template <class F, class... Args> void AddTask(F&& f, Args&&... args) { { std::lock_guard<std::mutex> lk(in_fly_mutex_); ++in_fly_; } std::lock_guard<std::mutex> lk(task_queue_mutex_); task_queue_.emplace( std::bind(std::forward<F>(f), std::forward<Args>(args)...)); task_queue_cv_.notify_one(); } // 等待线程池中的任务执行结束 void Wait() { std::unique_lock<std::mutex> lk(in_fly_mutex_); in_fly_cv_.wait(lk, [this] { return this->in_fly_ == 0; }); printf("-- %d --\n", in_fly_); } private: // 执行完队列中所有的任务后，再退出 void Stop() { stop_ = true; { std::lock_guard<std::mutex> lk(task_queue_mutex_); task_queue_cv_.notify_all(); } for (auto& e : threads_) { e.join(); } threads_.clear(); } void ThreadCb() { while (1) { std::unique_lock<std::mutex> lk(task_queue_mutex_); task_queue_cv_.wait(lk, [this] { return !task_queue_.empty() || stop_; }); // 只要队列中还有任务，就不退出 if (!task_queue_.empty()) { auto task = task_queue_.front(); task_queue_.pop(); lk.unlock(); InFlyGuard(*this); task(); } else { return; } } } private: bool stop_ = false; std::queue<std::function<void(void)>> task_queue_; std::mutex task_queue_mutex_; std::condition_variable task_queue_cv_; std::vector<std::thread> threads_; private: struct InFlyGuard { InFlyGuard(Pool& pool) : pool_(pool) {} ~InFlyGuard() { std::lock_guard<std::mutex> lk(pool_.in_fly_mutex_); --pool_.in_fly_; if (pool_.in_fly_ == 0) { pool_.in_fly_cv_.notify_all(); } } Pool& pool_; }; // 尚未结束的任务数 int in_fly_ = 0; std::mutex in_fly_mutex_; std::condition_variable in_fly_cv_; }; std::atomic<int> count{0}; void Add(int a, int b) { ++count; printf("%d\n", count.load(std::memory_order::memory_order_relaxed)); std::this_thread::sleep_for(std::chrono::milliseconds(800)); } void Sub(int a, int b) { --count; printf("%d\n", count.load(std::memory_order::memory_order_relaxed)); std::this_thread::sleep_for(std::chrono::milliseconds(800)); } int main() { Pool p(3); p.AddTask(Add, 2, 3); p.AddTask(Add, 2, 3); p.AddTask(Add, 2, 3); p.AddTask(Add, 2, 3); p.AddTask(Add, 2, 3); // 等待上面的任务结束 p.Wait(); printf("main thread, count: %d\n", count.load(std::memory_order::memory_order_relaxed)); p.AddTask(Sub, 9, 7); p.AddTask(Sub, 9, 7); p.AddTask(Sub, 9, 7); p.AddTask(Sub, 9, 7); p.AddTask(Sub, 9, 7); return 0; }
这段代码的 Wait 函数不符合预期，对比下面的代码：
#include <atomic> #include <chrono> #include <condition_variable> #include <functional> #include <future> #include <iostream> #include <memory> #include <mutex> #include <queue> #include <thread> #include <vector> class Pool { public: Pool(int n = std::thread::hardware_concurrency()) : size_(n) { for (int i = 0; i < n; ++i) { pool_.emplace_back(&Pool::thread_func, this); } } ~Pool() { Stop(); } template <class Func, class... Args> void AddTask(Func &&f, Args &&... args) { { std::unique_lock<std::mutex> lk(in_flight_mutex_); ++in_flight_; } std::unique_lock<std::mutex> lk(task_queue_mutex_); task_queue_.emplace( std::bind(std::forward<Func>(f), std::forward<Args>(args)...)); task_queue_cv_.notify_one(); } void Wait() { std::unique_lock<std::mutex> lk(in_flight_mutex_); in_flight_cv_.wait(lk, [this] { return in_flight_ == 0; }); } private: struct FlyGuard { FlyGuard(Pool &p) : p_(p) {} ~FlyGuard() { std::unique_lock<std::mutex> lk(p_.in_flight_mutex_); --p_.in_flight_; if (p_.in_flight_ == 0) { p_.in_flight_cv_.notify_all(); } } Pool &p_; }; void thread_func() { while (1) { std::unique_lock<std::mutex> lk(task_queue_mutex_); task_queue_cv_.wait(lk, [this] { return stop_ || !task_queue_.empty(); }); if (!task_queue_.empty()) { auto task = task_queue_.front(); task_queue_.pop(); lk.unlock(); FlyGuard fg(*this); task(); } else { return; } } } void Stop() { puts("stop"); stop_ = true; std::unique_lock<std::mutex> lk(task_queue_mutex_); task_queue_cv_.notify_all(); lk.unlock(); for (auto &e : pool_) { e.join(); } pool_.clear(); } private: bool stop_ = false; std::vector<std::thread> pool_; int size_; std::mutex task_queue_mutex_; std::condition_variable task_queue_cv_; std::queue<std::function<void(void)>> task_queue_; std::mutex in_flight_mutex_; std::condition_variable in_flight_cv_; int in_flight_ = 0; }; std::atomic<int> count{0}; void Add(int a, int b) { ++count; printf("%d\n", count.load(std::memory_order::memory_order_relaxed)); std::this_thread::sleep_for(std::chrono::milliseconds(800)); } void Sub(int a, int b) { --count; printf("%d\n", count.load(std::memory_order::memory_order_relaxed)); std::this_thread::sleep_for(std::chrono::milliseconds(800)); } int main() { Pool p(3); p.AddTask(Add, 2, 3); p.AddTask(Add, 2, 3); p.AddTask(Add, 2, 3); p.AddTask(Add, 2, 3); p.AddTask(Add, 2, 3); // 等待上面的任务结束 p.Wait(); printf("main thread, count: %d\n", count.load(std::memory_order::memory_order_relaxed)); p.AddTask(Sub, 9, 7); p.AddTask(Sub, 9, 7); p.AddTask(Sub, 9, 7); p.AddTask(Sub, 9, 7); p.AddTask(Sub, 9, 7); return 0; }
这一段就是在Wait那里明显停顿了一下，符合预期。
这两者代码逻辑一样，为啥表现不一样。。不得其解
调试了半天，发现是这里写错了
InFlyGuard(*this);
