c - c中的Producer_consumer使用p线程和信号量

Question

/*Producer_consumer problem in c using semaphores and pthreads*/


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

#define RAND_DIVISOR 100000000
#define TRUE 1

typedef int buffer_item;
#define BUFFER_SIZE 5

/* The mutex lock */
pthread_mutex_t mutex;

/* the semaphores */
sem_t full, empty;

/* the buffer */
buffer_item buffer[BUFFER_SIZE];

/* buffer counter */
int counter;

pthread_t tid;       //Thread ID
pthread_attr_t attr; //Set of thread attributes

void *producer(void *param); /* the producer thread */
void *consumer(void *param); /* the consumer thread */
void initializeData() {

   /* Create the mutex lock */
   pthread_mutex_init(&mutex, NULL);

   /* Create the full semaphore and initialize to 0 */
   sem_init(&full, 0, 0);

   /* Create the empty semaphore and initialize to BUFFER_SIZE */
   sem_init(&empty, 0, BUFFER_SIZE);

   /* Get the default attributes */
   pthread_attr_init(&attr);

   /* init buffer */
   counter = 0;
}

/* Producer Thread */
void *producer(void *param) {
   buffer_item item;

   while(TRUE) {
      /* sleep for a random period of time */
      int rNum = rand() / RAND_DIVISOR;
      sleep(rNum);

      /* generate a random number */
      item = rand();

      /* acquire the empty lock */
      sem_wait(&empty);
      /* acquire the mutex lock */
      pthread_mutex_lock(&mutex);

      if(insert_item(item)) {
         fprintf(stderr, " Producer report error condition\n");
      }
      else {
         printf("producer produced %d\n", item);
      }
      /* release the mutex lock */
      pthread_mutex_unlock(&mutex);
      /* signal full */
      sem_post(&full);
   }
}

/* Consumer Thread */
void *consumer(void *param) {
   buffer_item item;

   while(TRUE) {
      /* sleep for a random period of time */
      int rNum = rand() / RAND_DIVISOR;
      sleep(rNum);

      /* aquire the full lock */
      sem_wait(&full);
      /* aquire the mutex lock */
      pthread_mutex_lock(&mutex);
      if(remove_item(&item)) {
         fprintf(stderr, "Consumer report error condition\n");
      }
      else {
         printf("consumer consumed %d\n", item);
      }
      /* release the mutex lock */
      pthread_mutex_unlock(&mutex);
      /* signal empty */
      sem_post(&empty);
   }
}

/* Add an item to the buffer */
int insert_item(buffer_item item) {
   /* When the buffer is not full add the item
      and increment the counter*/
   if(counter < BUFFER_SIZE) {
      buffer[counter] = item;
      counter++;
      return 0;
   }
   else { /* Error the buffer is full */
      return -1;
   }
}

/* Remove an item from the buffer */
int remove_item(buffer_item *item) {
   /* When the buffer is not empty remove the item
      and decrement the counter */
   if(counter > 0) {
      *item = buffer[(counter-1)];
      counter--;
      return 0;
   }
   else { /* Error buffer empty */
      return -1;
   }
}

int main(int argc, char *argv[]) {
   /* Loop counter */
   int i;

   /* Verify the correct number of arguments were passed in */
   if(argc != 4) {
      fprintf(stderr, "USAGE:./main.out <INT> <INT> <INT>\n");
   }

   int mainSleepTime = atoi(argv[1]); /* Time in seconds for main to sleep */
   int numProd = atoi(argv[2]); /* Number of producer threads */
   int numCons = atoi(argv[3]); /* Number of consumer threads */

   /* Initialize the app */
   initializeData();

   /* Create the producer threads */
   for(i = 0; i < numProd; i++) {
      /* Create the thread */
      pthread_create(&tid,&attr,producer,NULL);
    }

   /* Create the consumer threads */
   for(i = 0; i < numCons; i++) {
      /* Create the thread */
      pthread_create(&tid,&attr,consumer,NULL);
   }

   /* Sleep for the specified amount of time in milliseconds */
   sleep(mainSleepTime);

   /* Exit the program */
   printf("Exit the program\n");
   exit(0);
}

当我使用 gcc 编译它时，出现以下错误:cse@cse-未指定:~/11011P0519$ vi producer_consumer2.c

cse@cse-Not-Specified:~/11011P0519$ gcc producer_consumer2.c

/tmp/ccu6fydZ.o:在函数“initializeData”中:

producer_consumer2.c:(.text+0x32): 对 `sem_init' 的 undefined reference

producer_consumer2.c:(.text+0x4e): 对 `sem_init' 的 undefined reference

/tmp/ccu6fydZ.o: 在函数“生产者”中:

producer_consumer2.c:(.text+0xac): 对 `sem_wait' 的 undefined reference

producer_consumer2.c:(.text+0x11d): 对 `sem_post' 的 undefined reference

/tmp/ccu6fydZ.o:在函数“消费者”中:

producer_consumer2.c:(.text+0x160): 对 `sem_wait' 的 undefined reference

producer_consumer2.c:(.text+0x1d1): 对 `sem_post' 的 undefined reference

/tmp/ccu6fydZ.o: 在函数“main”中:

producer_consumer2.c:(.text+0x2ef): 对 `pthread_create' 的 undefined reference

producer_consumer2.c:(.text+0x32d): 对 `pthread_create' 的 undefined reference

collect2: ld 返回了 1 个退出状态

当我尝试使用 gcc -lpthreads 时，我得到找不到 lpthread。

如何解决这个问题？

Answer 1

在使用 semphore.h 中的函数时，您需要使用 -lrt 或 -pthread 链接

编译如下

gcc producer_consumer2.c -pthread

参见 man sem_init