Linux多线程（七）读写锁

读写锁特点： 1）多个读者可以同时进行读 2）写者必须互斥（只允许一个写者写，也不能读者写者同时进行） 3）写者优先于读者（一旦有写者，则后续读者必须等待，唤醒时优先考虑写者） 互斥锁特点：

  一次只能一个线程拥有互斥锁，其他线程只有等待

源码如下：在这个例程中，运行结果和之前的互斥锁一样，下一文会讲述上读锁和写锁的区别

account.h

#ifndef __ACCOUNT_H__#define __ACCOUNT_H__#include <pthread.h>typedef struct{   int code;   double balance;   pthread_rwlock_t m_rw_lock;}Account;extern Account * create_account(int code,double balance);extern void destroy_account(Account *a);extern double with_draw(Account *a,double amt);extern double depoist(Account *a,double amt);extern double get_balance(Account *a);

#endif

account.c

#include "account.h"#include <assert.h>#include <malloc.h>#include <string.h>Account *create_account(int code, double balance){   Account *r=(Account *)malloc(sizeof(Account));   assert(r!=NULL);   r->code=code;   r->balance=balance;   pthread_rwlock_init(&r->m_rw_lock,NULL);   return r;}void destroy_account(Account *a){   assert(a!=NULL);   pthread_rwlock_destroy(&a->m_rw_lock);   free(a);}double with_draw(Account *a, double amt){   assert(a!=NULL);   pthread_rwlock_wrlock(&a->m_rw_lock);   if(amt > a->balance || amt<0){      pthread_rwlock_unlock(&a->m_rw_lock);      return 0.0;   }   double balance=a->balance;   sleep(1);

   balance = balance - amt;

   a->balance = balance;   pthread_rwlock_unlock(&a->m_rw_lock);   return amt;}double depoist(Account *a, double amt){   assert(a!=NULL);   if(amt<0){      return 0.0;   }   pthread_rwlock_wrlock(&a->m_rw_lock);   double balance=a->balance;   sleep(1);   balance = balance + amt;   a->balance = balance;   pthread_rwlock_unlock(&a->m_rw_lock);   return amt;}