线程或者进程同步semaphore

1.线程同步实例代码 semaphore.c

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

pthread_t tid1,tid2;
sem_t enablepush,enablepop;
pthread_mutex_t mtx;

volatile int buffer[100];
volatile int count=0;

void* producerFun(void*){
    int item;
    struct timespec t;
    t.tv_nsec=10000000UL;
    t.tv_sec=0UL;
    for(int i=0;i<100;++i){
        item=rand()%10000;
        sem_wait(&enablepush);
        pthread_mutex_lock(&mtx);
            buffer[count]=item;
            printf("Producer push %d into buffer[%d]\n",item,count++);
        pthread_mutex_unlock(&mtx);
        sem_post(&enablepop);
        if(i/10%2==0)
            t.tv_sec=1UL;
        else
            t.tv_sec=0UL;
        nanosleep(&t,NULL);
    }
    return 0;
}
void* consumerFun(void*){
    int item;
    struct timespec t;
    t.tv_nsec=1000000UL;
    t.tv_sec=0UL;
    for(int i=0;i<100;++i)
    {
        sem_wait(&enablepop);
        pthread_mutex_lock(&mtx);
            item=buffer[--count];
            printf("Consumer pop %d from buffer[%d]\n",item,count);
        pthread_mutex_unlock(&mtx);
        sem_post(&enablepush);
        if(i/10%2==1)
            t.tv_sec=1UL;
        else
            t.tv_sec=0UL;
        nanosleep(&t,NULL);
    }
    return 0;
}

int main(){
    pthread_create(&tid1,NULL,producerFun,NULL);
    pthread_create(&tid2,NULL,consumerFun,NULL);
    sem_init(&enablepush,0,100);
    sem_init(&enablepop,0,0);
    pthread_join(tid1,NULL);
    pthread_join(tid2,NULL);
    sem_destroy(&enablepush);
    sem_destroy(&enablepop);
    pthread_mutex_destroy(&mtx);
    return 0;
}

2.进程同步实例代码 producer.c和consumer.c

//producer.c
#include<stdlib.h>
#include<stdio.h>
#include<unistd.h>
#include<fcntl.h>
#include<semaphore.h>
#include<stdbool.h>

sem_t *empty, *full;

int main(){
    empty=sem_open("empty", O_CREAT|O_RDWR, 0666,0);//Create sem_t empty and init 0
    if(SEM_FAILED==empty){
        perror("sem_open_empty");
        exit(EXIT_FAILURE);
    }

    full =sem_open("full",  O_CREAT|O_RDWR, 0666,1);//Create sem_t full and init 1
    if(SEM_FAILED==full){
        perror("sem_open_full");
        exit(EXIT_FAILURE);
    }
    
    int count=0;
    while(true){
        sem_wait(full);
            //Critical Region where proucer goes into and consumer being blocked
            printf("\033[2J\033[H\033[38;2;255;255;125mProducer goes into Critial Region which protected by semaphore for the %dth time.\n",count++);
        sem_post(empty);
        sleep(1);
    }

    return 0;
}

//consumer.c
#include<stdlib.h>
#include<stdio.h>
#include<fcntl.h>
#include<unistd.h>
#include<semaphore.h>
#include<stdbool.h>

sem_t *empty, *full;

int main(){
    empty=sem_open("empty",0);//Access to existing sem_t empty
    if(SEM_FAILED==empty){
        perror("sem_open_empty");
        exit(EXIT_FAILURE);
    }

    full =sem_open("full" ,0);//Access to existing sem_t full
    if(SEM_FAILED==full){
        perror("sem_open_full");
        exit(EXIT_FAILURE);
    }
    
    int count=0;
    while(true){
        sem_wait(empty);
            //Critical Region where consumer goes into and producer being blocked
            printf("\033[2J\033[H\033[38;2;125;255;255mConsumer goes into Critical Region which protected by semaphore for the %dth time.\n",count++);
        sem_post(full);
    }
    
    return 0;
}

运行结果：