线程相关函数(5)-pthread_rwlock_rdlock(),pthread_rwlock_wrlock() 读写锁

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pthread_rwlock_t
pthread_rwlock_init
pthread_rwlock_destroy
pthread_rwlock_rdlock
pthread_rwlock_wrlock
pthread_rwlock_tryrdlock
pthread_rwlock_trywrlock
pthread_rwlock_unlock

示例代码：

#include <pthread.h>
#include <stdio.h>
#include <unistd.h>

static int counter;
static pthread_rwlock_t rwlock;

void *th_write(void *arg)
{
    int t, i;
    for (i=0; i<5; i++) {
        pthread_rwlock_wrlock(&rwlock);
        t = counter;
        usleep(100);
        printf("Write Thread(%x) counter=%d, ++counter=%d
", (int)pthread_self(), t, ++counter);
        pthread_rwlock_unlock(&rwlock);
        usleep(100);
    }

}


void *th_read(void *arg)
{
    while(1) {
        pthread_rwlock_rdlock(&rwlock);
        printf("Read Thread(%x) counter=%d
", (int)pthread_self(), counter);
        pthread_rwlock_unlock(&rwlock);
        usleep(100);
    }
}


int main()
{
    int i;
    pthread_t tid[8];    

    pthread_rwlock_init(&rwlock, NULL);
    for (i=0; i<3; i++)
        pthread_create(&tid[i], NULL, th_write, NULL);
    for (i=0; i<5; i++)
        pthread_create(&tid[i+3], NULL, th_read, NULL);
    for (i=0; i<8; i++)
        pthread_join(tid[i], NULL);

    pthread_rwlock_destroy(&rwlock);    
    return 0;
}

运行结果：

Read Thread(f901e700) counter=0
Read Thread(f981f700) counter=0
Read Thread(f881d700) counter=0
Read Thread(fa020700) counter=0
Read Thread(fa821700) counter=0
Write Thread(fb022700) counter=0, ++counter=1
Write Thread(fb823700) counter=1, ++counter=2
Write Thread(fc024700) counter=2, ++counter=3
Write Thread(fb022700) counter=3, ++counter=4
Write Thread(fb823700) counter=4, ++counter=5
Write Thread(fc024700) counter=5, ++counter=6
Write Thread(fb022700) counter=6, ++counter=7
Write Thread(fb823700) counter=7, ++counter=8
Write Thread(fc024700) counter=8, ++counter=9
Write Thread(fb022700) counter=9, ++counter=10
Write Thread(fb823700) counter=10, ++counter=11
Write Thread(fc024700) counter=11, ++counter=12
Write Thread(fb022700) counter=12, ++counter=13
Write Thread(fb823700) counter=13, ++counter=14
Write Thread(fc024700) counter=14, ++counter=15
Read Thread(f901e700) counter=15
Read Thread(f981f700) counter=15
Read Thread(f881d700) counter=15
Read Thread(fa020700) counter=15
Read Thread(fa821700) counter=15
Read Thread(f901e700) counter=15
Read Thread(f981f700) counter=15
Read Thread(f881d700) counter=15
Read Thread(fa020700) counter=15

...