我正在尝试创建一个消费者生产者程序，其中消费者线程生产者编号填充数组，而消费者线程打印填充数组的数字。目前，我可以填充数组并在消费者/生产者线程之间来回传递数据，但我希望生产者创建数字的速度快于消费者处理它们的速度。
此刻，每1秒生成一个数字，每3个消耗一个数字。在消耗一个数字之前应生成两个数字，但我的生产者线程正在等待它生成的数字被消耗。
我试过移动互斥锁和解锁，以及信号，但我还没有开始工作。以下代码生成以下输出：
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>
#include <unistd.h>
struct Data {
int num;
int wait_time;
};
pthread_mutex_t the_mutex;
pthread_cond_t condc, condp;
//int count = 0;
struct Data buffer[32];
void* producer(void *ptr) {
int i, w; /* counter and random wait time */
struct Data data;
int count = 0;
while(1) {
//w = rand() % 5 + 3;
w = 1;
sleep(w); /* Wait between 3 and 7 seconds */
data.num = rand() % 1000; /* Create random number to pass */
//data.wait_time = rand() % 8 + 2;
data.wait_time = 3;
pthread_mutex_lock(&the_mutex); /* lock the buffer */
while (buffer[count].num != 0) { /* while full */
//pthread_cond_signal(&condc);
pthread_cond_wait(&condp, &the_mutex);
}
//pthread_mutex_lock(&the_mutex); /* lock the buffer */
buffer[count] = data;
pthread_cond_signal(&condc); /* signal consumer */
pthread_mutex_unlock(&the_mutex);
printf("Produced %i and slept for %i seconds\n", buffer[count].num, w);
if (count != 31){
count += 1;
//printf("Producer count: %i\n", count);
}
else
count = 0;
//pthread_cond_signal(&condc); /* signal consumer */
//pthread_mutex_unlock(&the_mutex); /* unlock */
}
pthread_exit(0);
}
void* consumer(void *ptr) {
int i;
int count = 0;
//for(i = 1; i <= MAX; i++) {
while(1) {
pthread_mutex_lock(&the_mutex); /* lock th buffer */
while(buffer[count].num == 0){
//pthread_cond_signal(&condp); /* while empty */
pthread_cond_wait(&condc, &the_mutex);
}
//pthread_mutex_lock(&the_mutex);
sleep(buffer[count].wait_time);
printf("Consumed %i and slept for %i seconds\n", buffer[count].num, buffer[count].wait_time);
//pthread_mutex_lock(&the_mutex);
buffer[count].num = 0;
buffer[count].wait_time = 0;
pthread_cond_signal(&condp); /* signal producer */
pthread_mutex_unlock(&the_mutex);
if(count != 31){
count += 1;
//printf("Consumer count: %i\n", count);
}
else
count = 0;
//pthread_cond_signal(&condp); /* signal producer */
//pthread_mutex_unlock(&the_mutex); /* unlock */
}
pthread_exit(0);
}
int main(int argc, char **argv) {
pthread_t pro, con;
srand(time(NULL));
for (int i = 0; i < 32; i++) { /* Initialize buffer */
buffer[i].num = 0;
buffer[i].wait_time = 0;
}
// Initialize the mutex and condition variables
/* What's the NULL for ??? */
pthread_mutex_init(&the_mutex, NULL);
pthread_cond_init(&condc, NULL); /* Initialize consumer condition variable */
pthread_cond_init(&condp, NULL); /* Initialize producer condition variable */
// Create the threads
pthread_create(&con, NULL, consumer, NULL);
pthread_create(&pro, NULL, producer, NULL);
// Wait for the threads to finish
// Otherwise main might run to the end
// and kill the entire process when it exits.
pthread_join(con, NULL);
pthread_join(pro, NULL);
//pthread_join(&con, NULL);
//pthread_join(&pro, NULL);
// Cleanup -- would happen automatically at end of program
pthread_mutex_destroy(&the_mutex); /* Free up the_mutex */
pthread_cond_destroy(&condc); /* Free up consumer condition variable */
pthread_cond_destroy(&condp); /* Free up producer condition variable */
}
输出（程序在1秒后打印第1行，然后在3秒后同时打印第2行和第3行）：
Produced 985 and slept for 1 seconds
Consumed 985 and slept for 3 seconds
Produced 540 and slept for 1 seconds
我希望输出看起来像这样：
Produced 985 and slept for 1 seconds
Produced 540 and slept for 1 seconds
Consumed 985 and slept for 3 seconds
答案 0 :(得分：2)
消费者锁定互斥锁然后睡眠3秒钟。因此，制作人必须等待消费者完成工作/睡眠才能产生其他东西。当锁定到位时，避免睡觉任何一个线程。
编辑： 刚刚编辑了你的代码，这似乎没有信号等工作。试一试：
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>
#include <unistd.h>
struct Data {
int num;
int wait_time;
};
pthread_mutex_t the_mutex;
pthread_cond_t condc, condp;
struct Data buffer[32];
void* producer(void *ptr) {
int i, w; /* counter and random wait time */
struct Data data;
int count = 0;
while(1) {
printf("prod count %d\n",count);
w = 1;
sleep(w);
data.num = rand() % 1000;
data.wait_time = 3;
while (buffer[count].num != 0) {
printf("buffer full, count = %d\n", count);
sleep(1);
}
// Only using the mutex when we want to change the variable.
pthread_mutex_lock(&the_mutex);
buffer[count] = data;
pthread_mutex_unlock(&the_mutex);
printf("Produced %i and slept for %i seconds\n", buffer[count].num, w);
if (count != 31){
count += 1;
}
else
count = 0;
}
pthread_exit(0);
}
void* consumer(void *ptr) {
int i;
int count = 0;
while(1) { /* lock th buffer */
printf("cons count %d\n",count);
while(buffer[count].num == 0){
printf("buffer empty, count = %d\n", count);
sleep(1);
}
sleep(buffer[count].wait_time);
printf("Consumed %i and slept for %i seconds\n", buffer[count].num, buffer[count].wait_time);
pthread_mutex_lock(&the_mutex);
buffer[count].num = 0;
buffer[count].wait_time = 0;
pthread_mutex_unlock(&the_mutex);
if(count != 31){
count += 1;
//printf("Consumer count: %i\n", count);
}
else {
count = 0;
}
}
pthread_exit(0);
}
int main(int argc, char **argv) {
pthread_t pro, con;
srand(time(NULL));
for (int i = 0; i < 32; i++) { /* Initialize buffer */
buffer[i].num = 0;
buffer[i].wait_time = 0;
}
// Initialize the mutex and condition variables
/* What's the NULL for ??? */
pthread_mutex_init(&the_mutex, NULL);
pthread_cond_init(&condc, NULL); /* Initialize consumer condition variable */
pthread_cond_init(&condp, NULL); /* Initialize producer condition variable */
// Create the threads
pthread_create(&con, NULL, consumer, NULL);
pthread_create(&pro, NULL, producer, NULL);
// Wait for the threads to finish
// Otherwise main might run to the end
// and kill the entire process when it exits.
pthread_join(con, NULL);
pthread_join(pro, NULL);
//pthread_join(&con, NULL);
//pthread_join(&pro, NULL);
// Cleanup -- would happen automatically at end of program
pthread_mutex_destroy(&the_mutex); /* Free up the_mutex */
pthread_cond_destroy(&condc); /* Free up consumer condition variable */
pthread_cond_destroy(&condp); /* Free up producer condition variable */
}