条件变量 

 1 #include <pthread.h>
 2 #include <errno.h>
 3 #include <unistd.h>
 4 #include <list>
 5 #include <semaphore.h>
 6 #include <iostream>
 7 class Task
 8 {
 9 public:
10     Task(int taskID)
11     {
12         this->taskID = taskID;
13     }
14     void doTask()
15     {
16         std::cout << "handle a task, taskID: " << taskID <<
17             ", threadID: " << pthread_self() << std::endl;
18     }private:
19         int taskID;
20 };
21 pthread_mutex_t mymutex;
22 std::list<Task*> tasks;
23 pthread_cond_t mycv;
24 void* consumer_thread(void* param)
25 {
26     Task* pTask = NULL;
27     while (true)
28     {
29         pthread_mutex_lock(&mymutex);
30         while (tasks.empty())
31         {
32             //如果获得了互斥锁，但是条件不合适的话，pthread_cond_wait 会释放锁，不往下执行
33             //当发生变化后，条件合适， pthread_cond_wait 将直接获得锁
34             pthread_cond_wait(&mycv, &mymutex);
35         }
36         pTask = tasks.front(); 
37         tasks.pop_front();
38         pthread_mutex_unlock(&mymutex);
39         if (pTask == NULL)
40             continue;
41         pTask->doTask();
42         delete pTask;
43         pTask = NULL;
44     }
45     return NULL;
46 }
47 void* producer_thread(void* param)
48 {
49     int taskID = 0;
50     Task* pTask = NULL;
51     while (true)
52     {
53         pTask = new Task(taskID); 
54         pthread_mutex_lock(&mymutex);
55         tasks.push_back(pTask);
56         std::cout << "produce a task, taskID: " << taskID
57             << ", threadID: " << pthread_self() << std::endl;
58         pthread_mutex_unlock(&mymutex);
59         //释放信号量，通知消费者线程
60         pthread_cond_signal(&mycv);
61         taskID++;
62         //休眠 1 秒
63         sleep(1);
64     }
65     return NULL;
66 }
67 int main()
68 {
69     pthread_mutex_init(&mymutex, NULL);
70     pthread_cond_init(&mycv, NULL);//创建 5 个消费者线程
71     pthread_t consumerThreadID[5];
72     for (int i = 0; i < 5; ++i)
73     {
74         pthread_create(&consumerThreadID[i], NULL,
75             consumer_thread, NULL);
76     }
77     //创建一个生产者线程
78     pthread_t producerThreadID;
79     pthread_create(&producerThreadID, NULL,
80         producer_thread, NULL);
81     pthread_join(producerThreadID, NULL);
82     for (int i = 0; i < 5; ++i)
83     {
84         pthread_join(consumerThreadID[i], NULL);
85     }
86     pthread_cond_destroy(&mycv);
87     pthread_mutex_destroy(&mymutex);
88     return 0;
89 }
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posted @ 2022-01-13 11:10  PanDai  阅读(36)  评论(0)    收藏  举报