下面的案例是多个线程访问一个公共缓冲的处理，采用读写锁。需要注意的是代码中注释的地方。起初是将sleep放在unlock之前，这样的问题是，每次读线程读取完之后就直接睡眠导致写线程得到不到锁。由于写线程的写锁是独占的，需要保证读写锁没有被其他线程占用。
#include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <string.h> #include <time.h> pthread_rwlock_t rwlock; char *contents = NULL; void *worker(void *arg) { char *worker_name = (char *)arg; while(1) { pthread_rwlock_rdlock(&rwlock); printf("%s need to work, time[%s]\n", worker_name, contents); //这里需要注意--------------------- pthread_rwlock_unlock(&rwlock); sleep(1); } return (void *)0; } void *timer(void *arg) { while(1) { time_t tt = time(NULL); pthread_rwlock_wrlock(&rwlock); memset(contents, 0x0, 64 * sizeof(char)); ctime_r(&tt, contents); if (contents[strlen(contents) -1] == '\n') { contents[strlen(contents) -1] = 0; } pthread_rwlock_unlock(&rwlock); } pthread_exit((void *)0); } int main() { pthread_t rd_th1, rd_th2, rd_th3; pthread_t wr_th1; contents = (char *)malloc(64 * sizeof(char)); if (!contents) { printf("malloc error\n"); return -1; } memset(contents, 0x0, 64 * sizeof(char)); pthread_rwlock_init(&rwlock, NULL); pthread_create(&rd_th1, NULL, worker, (void *)"lily"); pthread_create(&rd_th2, NULL, worker, (void *)"hanmeimei"); pthread_create(&rd_th3, NULL, worker, (void *)"lucy"); pthread_create(&wr_th1, NULL, timer, NULL); pthread_join(rd_th1, NULL); pthread_join(rd_th2, NULL); pthread_join(rd_th3, NULL); pthread_join(wr_th1, NULL); pthread_rwlock_destroy(&rwlock); return 0; }
