C语言 使用信号量和pthreads的生产者消费者程序
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Producer Consumer program using semaphores and pthreads
提问by Twity 56876
I have written a code for producer-consumer problem.But I am not getting the output.There is no compilation error,but warning in my program.I am confused.Trying very hard.But can't get it.Please tell me what is wrong in my program.What will be the correct program.I am getting frustrated.Please help guys. Here is the code-
我已经写了一个生产者-消费者问题的代码。但我没有得到输出。没有编译错误，但我的程序中有警告。我很困惑。很努力。但无法得到它。请告诉我什么我的程序有问题。正确的程序是什么。我很沮丧。请帮助伙计们。这是代码-
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include </usr/include/semaphore.h>
#define BUFF_SIZE 5 /* total number of slots */
#define NP 3 /* total number of producers */
#define NC 3 /* total number of consumers */
#define NITERS 4 /* number of items produced/consumed */
typedef struct {
int buf[BUFF_SIZE]; /* shared var */
int in; /* buf[in%BUFF_SIZE] is the first empty slot */
int out; /* buf[out%BUFF_SIZE] is the first full slot */
sem_t full; /* keep track of the number of full spots */
sem_t empty; /* keep track of the number of empty spots */
sem_t mutex; /* enforce mutual exclusion to shared data */
} sbuf_t;
sbuf_t shared;
void *Producer(void *arg) {
int i, item, index;
index = (int) arg;
for (i = 0; i < NITERS; i++) {
/* Produce item */
item = i;
/* Prepare to write item to buf */
/* If there are no empty slots, wait */
sem_wait(&shared.empty);
/* If another thread uses the buffer, wait */
sem_wait(&shared.mutex);
shared.buf[shared.in] = item;
shared.in = (shared.in+1)%BUFF_SIZE;
printf("[P%d] Producing %d ...\n", index, item); fflush(stdout);
/* Release the buffer */
sem_post(&shared.mutex);
/* Increment the number of full slots */
sem_post(&shared.full);
/* Interleave producer and consumer execution */
if (i % 2 == 1) sleep(1);
}
return NULL;
}
void *Consumer(void *arg) {
int i, item, index;
index = (int) arg;
for (i = NITERS; i > 0; i--) {
sem_wait(&shared.full);
sem_wait(&shared.mutex);
item = i;
item = shared.buf[shared.out];
shared.out = (shared.out + 1) % BUFF_SIZE;
printf("[C%d] Consuming %d ...\n", index, item); fflush(stdout);
/* Release the buffer */
sem_post(&shared.mutex);
/* Increment the number of full slots */
sem_post(&shared.empty);
/* Interleave producer and consumer execution */
if (i % 2 == 1) sleep(1);
}
return NULL;
}
int main() {
pthread_t idP, idC;
int index;
sem_init(&shared.full, 0, 0);
sem_init(&shared.empty, 0, BUFF_SIZE);
pthread_mutex_init(&shared.mutex, NULL);
for (index = 0; index < NP; index++) {
/* Create a new producer */
pthread_create(&idP, NULL, Producer, (void*)index);
}
/*create a new Consumer*/
for (index = 0;index < NC;index++) {
pthread_create(&idC, NULL, Consumer, (void*)index);
}
pthread_exit(NULL);
}
回答by user2859193
Maybe you should take the Compiler warnings more serious. Incorrect types and undefined functions are usually shown as warning...
也许您应该更认真地对待编译器警告。不正确的类型和未定义的函数通常显示为警告...
I haven't checked the Logic of your program, but the principle should work:
我还没有检查你程序的逻辑，但原理应该是有效的：
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include </usr/include/semaphore.h>
// for sleep
#include <unistd.h>
#define BUFF_SIZE 5 /* total number of slots */
#define NP 3 /* total number of producers */
#define NC 3 /* total number of consumers */
#define NITERS 4 /* number of items produced/consumed */
typedef struct
{
int buf[BUFF_SIZE]; /* shared var */
int in; /* buf[in%BUFF_SIZE] is the first empty slot */
int out; /* buf[out%BUFF_SIZE] is the first full slot */
sem_t full; /* keep track of the number of full spots */
sem_t empty; /* keep track of the number of empty spots */
// use correct type here
pthread_mutex_t mutex; /* enforce mutual exclusion to shared data */
} sbuf_t;
sbuf_t shared;
void *Producer(void *arg)
{
int i, item, index;
index = (int)arg;
for (i=0; i < NITERS; i++)
{
/* Produce item */
item = i;
/* Prepare to write item to buf */
/* If there are no empty slots, wait */
sem_wait(&shared.empty);
/* If another thread uses the buffer, wait */
pthread_mutex_lock(&shared.mutex);
shared.buf[shared.in] = item;
shared.in = (shared.in+1)%BUFF_SIZE;
printf("[P%d] Producing %d ...\n", index, item);
fflush(stdout);
/* Release the buffer */
pthread_mutex_unlock(&shared.mutex);
/* Increment the number of full slots */
sem_post(&shared.full);
/* Interleave producer and consumer execution */
if (i % 2 == 1) sleep(1);
}
return NULL;
}
void *Consumer(void *arg)
{
int i, item, index;
index = (int)arg;
for (i=NITERS; i > 0; i--) {
sem_wait(&shared.full);
pthread_mutex_lock(&shared.mutex);
item=i;
item=shared.buf[shared.out];
shared.out = (shared.out+1)%BUFF_SIZE;
printf("[C%d] Consuming %d ...\n", index, item);
fflush(stdout);
/* Release the buffer */
pthread_mutex_unlock(&shared.mutex);
/* Increment the number of full slots */
sem_post(&shared.empty);
/* Interleave producer and consumer execution */
if (i % 2 == 1) sleep(1);
}
return NULL;
}
int main()
{
pthread_t idP, idC;
int index;
sem_init(&shared.full, 0, 0);
sem_init(&shared.empty, 0, BUFF_SIZE);
pthread_mutex_init(&shared.mutex, NULL);
for (index = 0; index < NP; index++)
{
/* Create a new producer */
pthread_create(&idP, NULL, Producer, (void*)index);
}
/*create a new Consumer*/
for(index=0; index<NC; index++)
{
pthread_create(&idC, NULL, Consumer, (void*)index);
}
pthread_exit(NULL);
}
I hope this helps.
我希望这有帮助。
回答by typelogic
There are still compiler warnings. The correct way to get the integer value from a void pointer is:
仍然有编译器警告。从 void 指针获取整数值的正确方法是：
index = *(int*)arg;
And, also to pass an integer pointer, is below:
而且，还要传递一个整数指针，如下：
pthread_create(&idC,NULL,Consumer,(void*)&index);
I still have some doubts as to how the Consumer or the Producer thread will receive the passed integer value since that is an address of the index variable in the forloop in the main thread. As soon as index gets incremented, the Consumer or Producer thread is affected by this increment.
我仍然对消费者或生产者线程如何接收传递的整数值有一些疑问，因为这是for主线程中循环中索引变量的地址。一旦索引增加，消费者或生产者线程就会受到这个增量的影响。
