多读者多写者

这个代码实现功能是：有写者在写时其他的写者不能再写，当写者全部写完时，读者才能继续读，当读者全部读完时写者才能继续写，写者每个循环写一次，读者每个循环读一次。
#include<pthread.h>
#include<string.h>
#include<stdlib.h>
#include<stdio.h>
#include<semaphore.h>
typedef struct
{
    int value;
    sem_t sem,semw;
    int sign,signw;
}Storage;
void set_data(Storage *s,int value)
{
    s->value=value;
}

int get_data(Storage* s)
{
    return s->value;
}

void* rd1_fn(void *arg)
{
    Storage *s=(Storage*)arg;
    int i=0;
    for(;i<1000;i++)
    {
        sem_wait(&s->sem);
        s->sign++;
        int value=get_data(s);
        usleep(30000);
        printf("rd1(0x)%lx read data :%d
",pthread_self(),value);
        if(s->sign!=3)
        sem_post(&s->sem);
        else
        {
            sem_post(&s->semw);
            s->signw=0;
        }
        usleep(30000);
        //sleep(4);
    }
    return (void*)0;
}
void* rd2_fn(void *arg)
{
    Storage *s=(Storage*)arg;
    int i=0;
    for(;i<1000;i++)
    {
        sem_wait(&s->sem);
        s->sign++;
        int value=get_data(s);
        usleep(30000);
        printf("rd2(0x)%lx read data :%d
",pthread_self(),value);
        if(s->sign!=3)
        sem_post(&s->sem);
        else
        {
            sem_post(&s->semw);
            s->signw=0;
        }
        usleep(30000);
        //sleep(1);
    }
    return (void*)0;
}
void* rd3_fn(void *arg)
{
    Storage *s=(Storage*)arg;
    int i=0;
    for(;i<1000;i++)
    {
        sem_wait(&s->sem);
        s->sign++;
        int value=get_data(s);
        usleep(30000);
        printf("rd3(0x)%lx read data :%d
",pthread_self(),value);
        if(s->sign!=3)
        sem_post(&s->sem);
        else
        {
            sem_post(&s->semw);
            s->signw=0;
        }
        usleep(30000);
        //sleep(2);
    }
    return (void*)0;
}

void* wt_fn(void *arg)
{
    Storage *s=(Storage*)arg;
    int i=0;
    for(;i<1000;i++)
    {
        sem_wait(&s->semw);
        s->sign=0;
        s->signw++;
        set_data(s,i+100);
        usleep(30000);
        printf("wt(0x)%lx wrote data :%d
",pthread_self(),i+100);
        if(s->signw!=2)
        sem_post(&s->semw);
        else
        sem_post(&s->sem);
        usleep(30000);
    //    sleep(5);
    }    
    return (void*)0;
}
void* wt_fn2(void *arg)
{
    Storage *s=(Storage*)arg;
    int i=0;
    for(;i<1000;i++)
    {
        sem_wait(&s->semw);
        s->sign=0;
        s->signw++;
        set_data(s,i+200);
        //sleep(30000);
        printf("wt2(0x)%lx wrote data :%d
",pthread_self(),i+200);
        if(s->signw!=2)
        sem_post(&s->semw);
        else
        sem_post(&s->sem);
        usleep(30000);
    //    sleep(5);
    }    
    return (void*)0;
}
int main(void)
{
    int err;
    pthread_t rd1,rd2,rd3,wt1,wt2;
    Storage s;
    s.value=0;
    s.sign=0;
    s.signw=0;
    sem_init(&s.sem,0,0);
    sem_init(&s.semw,0,1);
    pthread_create(&rd1,NULL,rd1_fn,(void*)&s);
    pthread_create(&rd2,NULL,rd2_fn,(void*)&s);
    pthread_create(&rd3,NULL,rd3_fn,(void*)&s);
    pthread_create(&wt1,NULL,wt_fn,(void*)&s);
    pthread_create(&wt2,NULL,wt_fn2,(void*)&s);
    pthread_join(rd1,NULL);
    pthread_join(rd2,NULL);
    pthread_join(rd3,NULL);
    pthread_join(wt1,NULL);
    pthread_join(wt2,NULL);
    sem_destroy(&s.sem);
    sem_destroy(&s.semw);
    return 0;
}

这个是写一万个数据时CPU的占有率为%1 

这个是写1000个数据时CPU的占有率，都是%1，与前者相同

改变写的数据的类型为字符串

#include<pthread.h>
#include<string.h>
#include<stdlib.h>
#include<stdio.h>
#include<semaphore.h>
typedef struct
{
    char* value;
    sem_t sem,semw;
    int sign,signw;
}Storage;
void set_data(Storage *s,char* value)
{
    s->value=value;
}

char* get_data(Storage* s)
{
    return s->value;
}

void* rd1_fn(void *arg)
{
    Storage *s=(Storage*)arg;
    int i=0;
    for(;i<1000;i++)
    {
        sem_wait(&s->sem);
        s->sign++;
        char* value=get_data(s);
        usleep(30000);
        printf("rd1(0x)%lx read data :%s
",pthread_self(),value);
        if(s->sign!=3)
        sem_post(&s->sem);
        else
        {
            sem_post(&s->semw);
            s->signw=0;
        }
        usleep(30000);
        //sleep(4);
    }
    return (void*)0;
}
void* rd2_fn(void *arg)
{
    Storage *s=(Storage*)arg;
    int i=0;
    for(;i<1000;i++)
    {
        sem_wait(&s->sem);
        s->sign++;
        char* value=get_data(s);
        usleep(30000);
        printf("rd2(0x)%lx read data :%s
",pthread_self(),value);
        if(s->sign!=3)
        sem_post(&s->sem);
        else
        {
            sem_post(&s->semw);
            s->signw=0;
        }
        usleep(30000);
        //sleep(1);
    }
    return (void*)0;
}
void* rd3_fn(void *arg)
{
    Storage *s=(Storage*)arg;
    int i=0;
    for(;i<1000;i++)
    {
        sem_wait(&s->sem);
        s->sign++;
        char* value=get_data(s);
        usleep(30000);
        printf("rd3(0x)%lx read data :%s
",pthread_self(),value);
        if(s->sign!=3)
        sem_post(&s->sem);
        else
        {
            sem_post(&s->semw);
            s->signw=0;
        }
        usleep(30000);
        //sleep(2);
    }
    return (void*)0;
}

void* wt_fn(void *arg)
{
    Storage *s=(Storage*)arg;
    int i=0;
    for(;i<1000;i++)
    {
        sem_wait(&s->semw);
        s->sign=0;
        s->signw++;
        strcat(s->value,"abc");
        //set_data(s,s->value);
        usleep(30000);
        printf("wt(0x)%lx wrote data :%s
",pthread_self(),s->value);
        if(s->signw!=2)
        sem_post(&s->semw);
        else
        sem_post(&s->sem);
        usleep(30000);
    //    sleep(5);
    }    
    return (void*)0;
}
void* wt_fn2(void *arg)
{
    Storage *s=(Storage*)arg;
    int i=0;
    for(;i<1000;i++)
    {
        sem_wait(&s->semw);
        s->sign=0;
        s->signw++;
        strcat(s->value,"cba");
        //set_data(s,i+200);
        //sleep(30000);
        printf("wt2(0x)%lx wrote data :%s
",pthread_self(),s->value);
        if(s->signw!=2)
        sem_post(&s->semw);
        else
        sem_post(&s->sem);
        usleep(30000);
    //    sleep(5);
    }    
    return (void*)0;
}
int main(void)
{
    int err;
    pthread_t rd1,rd2,rd3,wt1,wt2;
    Storage s;
    s.value=(char*)malloc(sizeof(char)*2048);
    s.sign=0;
    s.signw=0;
    sem_init(&s.sem,0,0);
    sem_init(&s.semw,0,1);
    pthread_create(&rd1,NULL,rd1_fn,(void*)&s);
    pthread_create(&rd2,NULL,rd2_fn,(void*)&s);
    pthread_create(&rd3,NULL,rd3_fn,(void*)&s);
    pthread_create(&wt1,NULL,wt_fn,(void*)&s);
    pthread_create(&wt2,NULL,wt_fn2,(void*)&s);
    pthread_join(rd1,NULL);
    pthread_join(rd2,NULL);
    pthread_join(rd3,NULL);
    pthread_join(wt1,NULL);
    pthread_join(wt2,NULL);
    sem_destroy(&s.sem);
    sem_destroy(&s.semw);
    return 0;
}

程序运行时CPU占有率略有提高到%2