读锁优先的实现-白红宇

读锁优先的实现

阅读量：5835 次

发布时间：2019-06-18

本文共 7609 字，大约阅读时间需要 25 分钟。

1、问题：在操作系统内对线程是写锁优先，如何实现读锁优先呢？

分析：的利用互斥量和条件变量来进行实现，由于已经对操作系统的写锁优先进行了实现，那么对其原理应该已经掌握了，直接代码实现。

代码如下：

(1)、utili.h

#include
     
      #include
      
       #include

(2)、pthread_rwlock.h

#ifndef _PTHREAD_RWLOCK_H#define _PTHREAD_RWLOCK_H#include"utili.h"enum {EINVAL, EBUSY};typedef struct{    pthread_mutex_t rw_mutex;    pthread_cond_t  rw_condreaders;    pthread_cond_t  rw_condwriters;    int             rw_magic;    int             rw_nwaitreaders;    int             rw_nwaitwriters;    int             rw_refcount;     //<0   ==0   >0}my_pthread_rwlock_t;#define RW_MAGIC 0x2016911#define MY_PTHREAD_RWLOCK_INITIALIZER {PTHREAD_MUTEX_INITIALIZER, \                                    PTHREAD_COND_INITIALIZER,  \                                    PTHREAD_COND_INITIALIZER, \                                    RW_MAGIC, \                                    0, 0, 0}typedef int my_pthread_rwlockattr_t;void reader_clean_up(void *arg);void writer_clean_up(void *arg);int my_pthread_rwlock_init(my_pthread_rwlock_t *rw, my_pthread_rwlockattr_t *at);int my_pthread_rwlock_destroy(my_pthread_rwlock_t *rw);int my_pthread_rwlock_rdlock(my_pthread_rwlock_t *rw);int my_pthread_rwlock_wrlock(my_pthread_rwlock_t *rw);int my_pthread_rwlock_unlock(my_pthread_rwlock_t *rw);int my_pthread_rwlock_tryrdlock(my_pthread_rwlock_t *rw);int my_pthread_rwlock_trywrlock(my_pthread_rwlock_t *rw);#endif

(3)、pthread_rwlock_init.c

#include"pthread_rwlock.h"int my_pthread_rwlock_init(my_pthread_rwlock_t *rw, my_pthread_rwlockattr_t *at){    int result;    if(at != NULL)        return EINVAL;    if((result = pthread_mutex_init(&rw->rw_mutex, NULL)) != 0)        goto err1;    if((result = pthread_cond_init(&rw->rw_condreaders, NULL)) != 0)        goto err2;    if((result = pthread_cond_init(&rw->rw_condwriters, NULL)) != 0)        goto err3;    rw->rw_nwaitreaders = 0;    rw->rw_nwaitwriters = 0;    rw->rw_refcount = 0;    rw->rw_magic = RW_MAGIC;    return 0;err3:    pthread_cond_destroy(&rw->rw_condreaders);err2:    pthread_mutex_destroy(&rw->rw_mutex);err1:    return result;}

(4)、pthread_rwlock_wrlock.c

#include"pthread_rwlock.h"int my_pthread_rwlock_wrlock(my_pthread_rwlock_t *rw){    int result;    if(rw->rw_magic != RW_MAGIC)        return EINVAL;    if((result = pthread_mutex_lock(&rw->rw_mutex)) != 0)        return result;    while(rw->rw_refcount!=0 || rw->rw_nwaitreaders>0){        rw->rw_nwaitwriters++;        result = pthread_cond_wait(&rw->rw_condwriters, &rw->rw_mutex);        rw->rw_nwaitwriters--;        if(result != 0){             break;        }       }       if(result == 0){         rw->rw_refcount = -1;     }       pthread_mutex_unlock(&rw->rw_mutex);    return result;}

(5)、pthread_rwlock_rdlock.c

#include"pthread_rwlock.h"int my_pthread_rwlock_rdlock(my_pthread_rwlock_t *rw){    int result;    if(rw->rw_magic != RW_MAGIC)        return EINVAL;    if((result = pthread_mutex_lock(&rw->rw_mutex)) != 0)        return result;    //while(rw->rw_refcount<0 || rw->rw_nwaitwriters>0)    while(rw->rw_refcount < 0){         rw->rw_nwaitreaders++;        //pthread_cleanup_push(reader_clean_up);        result = pthread_cond_wait(&rw->rw_condreaders, &rw->rw_mutex);        //pthread_cleanup_pop(0);        rw->rw_nwaitreaders--;        if(result != 0){             break;        }       }       if(result == 0){         rw->rw_refcount++;    }       pthread_mutex_unlock(&rw->rw_mutex);    return result;}

(6)、pthread_rwlock_trywrlock.c

#include"utili.h"#include"pthread_rwlock.h"int pthread_rwlock_trywrlock(my_pthread_rwlock_t *rw){   int result;   if(rw->rw_magic != RW_MAGIC){        return EINVAL;   }      if((result = pthread_mutex_lock(&rw->rw_mutex)) != 0){        return result;   }      if(rw->rw_refcount != 0){         result = EBUSY;   }else{        rw->rw_refcount = -1;    }      pthread_mutex_unlock(&rw->rw_mutex);   return result;}

(7)、pthread_rwlock_tryrdlock.c

#include"utili.h"#include"pthread_rwlock.h"int pthread_rwlock_tryrdlock(my_pthread_rwlock_t *rw){   int result;   if(rw->rw_magic != RW_MAGIC){        return EINVAL;   }      if((result = pthread_mutex_lock(&rw->rw_mutex)) != 0){        return result;   }      if(rw->rw_refcount < 0 || rw->rw_nwaitwriters > 0){         result = EBUSY;   }else{        rw->rw_refcount++;   }      pthread_mutex_unlock(&rw->rw_mutex);   return result;}

(8)、pthread_rwlock_unlock.c

#include"pthread_rwlock.h"int my_pthread_rwlock_unlock(my_pthread_rwlock_t *rw){    int result;    if(rw->rw_magic != RW_MAGIC)        return EINVAL;    if((result = pthread_mutex_lock(&rw->rw_mutex)) != 0)        return result;    if(rw->rw_refcount > 0){         rw->rw_refcount--;    }else if(rw->rw_refcount == -1){        rw->rw_refcount = 0;    }else{        printf("refcount error.\n");    }       if(rw->rw_nwaitreaders > 0){         result = pthread_cond_broadcast(&rw->rw_condreaders);    }else if(rw->rw_nwaitwriters > 0){         if(rw->rw_refcount == 0)            result = pthread_cond_signal(&rw->rw_condwriters);    }       //if(rw->rw_nwaitwriters > 0)    //{     //    if(rw->rw_refcount == 0)    //        result = pthread_cond_signal(&rw->rw_condwriters);    //}    //else if(rw->rw_nwaitreaders > 0)    //    result = pthread_cond_broadcast(&rw->rw_condreaders);    pthread_mutex_unlock(&rw->rw_mutex);    return result;}

(9)、pthread_rwlock_destroy.c

#include"pthread_rwlock.h"int my_pthread_rwlock_destroy(my_pthread_rwlock_t *rw){    if(rw->rw_magic != RW_MAGIC)        return EINVAL;    if(rw->rw_refcount!=0 || rw->rw_nwaitreaders!=0 || rw->rw_nwaitwriters!=0)        return EBUSY;    pthread_mutex_destroy(&rw->rw_mutex);    pthread_cond_destroy(&rw->rw_condreaders);    pthread_cond_destroy(&rw->rw_condwriters);    rw->rw_magic = 0;    return 0;}

(10)、test.c

#include"utili.h"#include"pthread_rwlock.h"my_pthread_rwlock_t rwlock = MY_PTHREAD_RWLOCK_INITIALIZER;void* fun1(void *arg){    my_pthread_rwlock_wrlock(&rwlock);    printf("This is fun1. wrlock\n");    sleep(5);    printf("fun1 wake up.\n");    my_pthread_rwlock_unlock(&rwlock);}void* fun2(void *arg){    my_pthread_rwlock_rdlock(&rwlock);    printf("This is fun2.rdlock.\n");    my_pthread_rwlock_unlock(&rwlock);}void* fun3(void *arg){    my_pthread_rwlock_wrlock(&rwlock);    printf("This is fun3,wrlock.\n");    my_pthread_rwlock_unlock(&rwlock);}int main(){    pthread_t tid1, tid2[5],tid3[5];    int i;    pthread_create(&tid1, NULL, fun1, NULL);    sleep(1);    for(i=0; i<5; ++i)    {        pthread_create(&tid2[i], NULL, fun2, NULL);    }    for(i=0; i<5; ++i)    {        pthread_create(&tid3[i], NULL, fun3, NULL);    }    pthread_join(tid1, NULL);    for(i=0; i<5; ++i)    {        pthread_join(tid2[i], NULL);        pthread_join(tid3[i], NULL);    }    return 0;}

(11)、Makefile

OBJ=test.o pthread_rwlock_rdlock.o pthread_rwlock_unlock.o pthread_rwlock_wrlock.o pthread_rwlock_init.oSRC=test.c pthread_rwlock_rdlock.c pthread_rwlock_unlock.c pthread_rwlock_wrlock.c pthread_rwlock_init.ctest:$(OBJ)    gcc -o test $(OBJ) -lpthreadtest.o:test.c    gcc -o test.o -c test.c -gpthread_rwlock_rdlock.o:pthread_rwlock_rdlock.c    gcc -o pthread_rwlock_rdlock.o -c pthread_rwlock_rdlock.c -gpthread_rwlock_unlock.o:pthread_rwlock_unlock.c    gcc -o pthread_rwlock_unlock.o -c pthread_rwlock_unlock.c -gpthread_rwlock_wrlock.o:pthread_rwlock_wrlock.c    gcc -o pthread_rwlock_wrlock.o -c pthread_rwlock_wrlock.cpthread_rwlock_init.o:pthread_rwlock_init.c    gcc -o pthread_rwlock_init.o -c pthread_rwlock_init.c.PHONY:cleanclean:    rm *.o test

运行结果

此时已经实现了读锁优先(只要对写锁优先熟悉，稍作更改就可以了)。

转载于:https://blog.51cto.com/wait0804/1855595

你可能感兴趣的文章

UVA - 825Walking on the Safe Side(dp)

查看>>

android大概是通过logcat拦截Log

查看>>

android HDMI 清晰度分辨率

查看>>

JQuery发送Put、Delete请求 - 摘自网络

查看>>