线程间的读写锁

共享独占：

读取锁——共享

写入锁——独占

即：读锁可以加多个；有写锁时，读写锁都加不上；有读锁时，可以加读锁而不能加写锁。

静态分配读写锁：

pthread_rwlock_t  rwlock = PTHREAD_RWLOCK_INITIALIZER；

动态分配读写锁：

pthread_rwlock_init（&rwlock，NULL）；
pthread_rwlock_destroy（&rwlock）；

加读取锁：

int pthread_rwlock_rdlock（pthread_rwlock_t*  rwlock）；
int pthread_rwlock_tryrdlock（pthread_rwlock_t*  rwlock）；

加写入锁：

int pthread_rwlock_wrlock（pthread_rwlock_t*  rwlock）；
int pthread_rwlock_trywrlock（pthread_rwlock_t*  rwlock）；

解锁：

int pthread_rwlock_unlock（pthread_rwlock_t*  rwlock）；

代码：

#include <stdio.h>#include <pthread.h>#include <time.h>pthread_rwlock_t rwlock = PTHREAD_RWLOCK_INITIALIZER;int count = 10000;int put_cur = 0;void* search(void* arg){pthread_rwlock_rdlock(&rwlock);printf("%d leave %d\n",(int)arg,count);//usleep(500000);pthread_rwlock_unlock(&rwlock);}void rollback(void* arg){count -= put_cur;printf("rollback %d  to %d\n",put_cur,count);pthread_rwlock_unlock(&rwlock);}void* put(void* arg){pthread_cleanup_push(rollback,NULL);pthread_rwlock_wrlock(&rwlock);put_cur = rand()%1000;count += put_cur;printf("%d put %d ok,leave %d\n",(int)arg,put_cur,count);//usleep(500000);pthread_rwlock_unlock(&rwlock);pthread_cleanup_pop(0);}void* hacker(void* arg){sleep(2);pthread_t* ptids = arg;pthread_cancel(ptids[0]);printf("\033[41;34mcancel %lu\033[0m\n",ptids[0]);}void* get(void* arg){pthread_rwlock_wrlock(&rwlock);int cur = rand()%1000;if(count>cur){count -= cur;printf("%d crash %d leave %d\n",(int)arg,cur,count);}else{printf("%d leave not enought %d\n",(int)arg,count);}//usleep(500000);pthread_rwlock_unlock(&rwlock);}int main(){pthread_t tids[100];typedef void*(*func_t)(void*);func_t func_arr[3] = {put,search,get};func_t funcs[100];pthread_setconcurrency(4);int i=0;srand(time(NULL));for(i=0;i<100;i++){funcs[i] = func_arr[rand()%3];}for(i=0;i<100;i++){pthread_create(&tids[i],NULL,funcs[i],i);}for(i=0;i<100;i++){pthread_join(tids[i],NULL);}}