thread同步测试

代码：

#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <semaphore.h>

#define NUM 5
int queue[NUM];
sem_t blank_number, product_number;

void *producer ( void * arg )
{
    static int p = 0;

    for ( ;; ) {
        sem_wait( &blank_number );
        queue[p] = rand() % 1000;
        printf("Product %d \n", queue[p]);
        p = (p+1) % NUM;
        sleep ( rand() % 5);
        sem_post( &product_number );
    }
}
void *consumer ( void * arg )
{

    static int c = 0;
    for( ;; ) {
        sem_wait( &product_number );
        printf("Consume %d\n", queue[c]);
        c = (c+1) % NUM;
        sleep( rand() % 5 );
        sem_post( &blank_number );
    }
}

int main(int argc, char *argv[] )
{
    pthread_t pid, cid;

    sem_init( &blank_number, 0, NUM );
    sem_init( &product_number, 0, 0);
    pthread_create( &pid, NULL, producer, NULL);
    pthread_create( &cid, NULL, consumer, NULL);
    pthread_join( pid, NULL );
    pthread_join( cid, NULL );
    sem_destroy( &blank_number );
    sem_destroy( &product_number );
    return 0;
}

运行截图：

代码功能：生产者与消费者资源提供和消耗。

修改后代码：

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

#define NUM 3
int queue[NUM];
sem_t blank_number, product_number,mutex;

void *producer ( void * arg )
{
    static int p = 0;

    for ( ;; ) {
        sem_wait( &blank_number );
        sem_wait( &mutex);
        queue[p] = rand() % 1000;
        printf("Product %d \n", queue[p]);
        p = (p+1) % NUM;
        sleep ( rand() % 5);
        sem_post(&mutex); 
        sem_post( &product_number );
    }
}
void *consumer ( void * arg )
{

    static int c = 0;
    for( ;; ) {
        sem_wait( &product_number );
        sem_wait(&mutex);
        printf("Consume %d\n", queue[c]);
        c = (c+1) % NUM;
        sleep( rand() % 5);
        sem_post(&mutex);
        sem_post( &blank_number );
    }
}

int main(int argc, char *argv[] )
{
    pthread_t pid, cid1,cid2,cid3,cid4,cid5;
    sem_init( &blank_number, 0, NUM );
    sem_init( &product_number, 0, 0);
    sem_init( &mutex, 1, 1);
    pthread_create( &pid, NULL, producer, NULL);
    pthread_create( &cid1, NULL, consumer, NULL);
    pthread_create( &cid2, NULL, consumer, NULL);
    pthread_create( &cid3, NULL, consumer, NULL);
    pthread_create( &cid4, NULL, consumer, NULL);
    pthread_create( &cid5, NULL, consumer, NULL);
    pthread_join( pid, NULL );
    pthread_join( cid1, NULL );
    pthread_join( cid2, NULL );
    pthread_join( cid3, NULL );
    pthread_join( cid4, NULL );
    pthread_join( cid5, NULL );
    sem_destroy( &blank_number );
    sem_destroy( &product_number );
    return 0;
}