linux线程同步--条件变量练习(1)

注意：消息是由主线程产生的，而消息这时候在栈中，两个线程通过全局变量获取访问消息。

Unix环境高级编程P288
进程的所有信息对该进程的所有线程都是共享的，包括可执行的程序文本、程序的全局变量和堆内存、栈以及文件描述符。

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#include <pthread.h>#include <stdio.h>struct msg {int data;struct msg *m_next;/* ... more stuff here ... */};struct msg *workq;pthread_cond_t qready = PTHREAD_COND_INITIALIZER;pthread_mutex_t qlock = PTHREAD_MUTEX_INITIALIZER;voidprocess_msg(void){struct msg *mp;for (;;) {pthread_mutex_lock(&qlock);while (workq == NULL)pthread_cond_wait(&qready, &qlock);mp = workq;workq = mp->m_next;pthread_mutex_unlock(&qlock);/* now process the message mp */printf("deal the mp. the data is %d\n",mp->data);}}voidenqueue_msg(struct msg *mp){pthread_mutex_lock(&qlock);mp->m_next = workq;workq = mp;pthread_mutex_unlock(&qlock);pthread_cond_signal(&qready);}void* thr_fn(void* arg){process_msg();return ((void*)1);}int main(){pthread_t tid1;pthread_t tid2;int err;err = pthread_create(&tid1,NULL,thr_fn,NULL);if(err !=0){err_quit("can't  create thread%s\n",strerror(err));}err = pthread_create(&tid2,NULL,thr_fn,NULL);if(err !=0){err_quit("cant' create thread%s\n",strerror(err));}printf("create success.\n");sleep(1);struct msg msg1;msg1.data = 110;msg1.m_next = NULL;workq = NULL;enqueue_msg(&msg1);printf("add a msg\n");sleep(3);//pthread_cancel(tid1);//pthread_cancel(tid2);printf("ok\n");}

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前面的程序访问的是主线程的栈区，下面的程序访问的是一个子线程的栈区。

可见线程之间是可以互相访问栈区的。

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#include <pthread.h>#include <stdlib.h>#include <stdio.h>struct msg {int data;struct msg *m_next;/* ... more stuff here ... */};struct msg *workq;pthread_cond_t qready = PTHREAD_COND_INITIALIZER;pthread_mutex_t qlock = PTHREAD_MUTEX_INITIALIZER;voidprocess_msg(void){struct msg *mp;for (;;) {pthread_mutex_lock(&qlock);while (workq == NULL)pthread_cond_wait(&qready, &qlock);mp = workq;workq = mp->m_next;pthread_mutex_unlock(&qlock);/* now process the message mp */printf("deal the mp. the data is %d\n",mp->data);}}voidenqueue_msg(struct msg *mp){pthread_mutex_lock(&qlock);mp->m_next = workq;workq = mp;pthread_mutex_unlock(&qlock);pthread_cond_signal(&qready);}void* thr_fn(void* arg){process_msg();return ((void*)1);}void* thr_fn2(void* arg){for(;;){struct msg temp;temp.data =120;temp.m_next = NULL;enqueue_msg(&temp);sleep(2);}}int main(){pthread_t tid1;pthread_t tid2;pthread_t tid3;int err;err = pthread_create(&tid1,NULL,thr_fn,NULL);if(err !=0){err_quit("can't  create thread%s\n",strerror(err));}err = pthread_create(&tid2,NULL,thr_fn,NULL);if(err !=0){err_quit("cant' create thread%s\n",strerror(err));}err = pthread_create(&tid3,NULL,thr_fn2,NULL);if(err!=0){err_quit("cant' create thread%s\n",strerror(err));}printf("create success.\n");//enqueue_msg(mp);//sleep(5);sleep(20);pthread_cancel(tid1);pthread_cancel(tid2);//pthread_cancel(tid1);//pthread_cancel(tid2);printf("ok\n");}

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