生产者，消费者互斥同步参考如下代码：
#include <stdio.h>#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
#include <error.h>
#include <semaphore.h>
#define PRODUCER_NUM 10
#define CONSUMER_MUM 8
#define BUFFER_SIZE 20
#define SLEEP_TIME 1
#define error_exit( _msg_ ) error(EXIT_FAILURE, errno, _msg_)
int print()
void *consumer_thread(void *args)
void *producer_thread(void *args)
sem_t can_produce
sem_t can_consume
pthread_mutex_t mutex
int produce_index = 0
int consume_index = 0
int producer_id = 0
int consumer_id = 0
int buffer[BUFFER_SIZE] = {0}
int main()
{
int i
pthread_t producer[PRODUCER_NUM]
pthread_t consumer[CONSUMER_MUM]
int sinit1 = sem_init(&can_produce, 0, BUFFER_SIZE)
int sinit2 = sem_init(&can_consume, 0, 0)
if(sinit1 || sinit2)
error_exit("sem_init")
if(pthread_mutex_init(&mutex, NULL))
error_exit("pthread_mutex_init")
for(i=0 i<PRODUCER_NUM i++)
if(pthread_create(&producer[i], NULL, producer_thread, NULL))
error_exit("pthread_create")
for(i=0 i<CONSUMER_MUM i++)
if(pthread_create(&consumer[i], NULL, consumer_thread, NULL))
error_exit("pthread_create")
for(i=0 i<PRODUCER_NUM i++)
pthread_join(producer[i], NULL)
for(i=0 i<CONSUMER_MUM i++)
pthread_join(consumer[i], NULL)
}
void *producer_thread(void *args)
{
int id = producer_id++
while(1){
sleep(SLEEP_TIME)
pthread_mutex_lock(&mutex)
sem_wait(&can_produce)
printf("Producer id %d in %d.\n", id, produce_index)
buffer[produce_index] = 1
produce_index = (produce_index + 1) % BUFFER_SIZE
print()
sem_post(&can_consume)
pthread_mutex_unlock(&mutex)
}
return NULL
}
void *consumer_thread(void *args)
{
int id = consumer_id++
while(1){
sleep(SLEEP_TIME)
pthread_mutex_lock(&mutex)
sem_wait(&can_consume)
printf("Consumer id %d in %d.\n", id, consume_index)
buffer[consume_index] = 0
consume_index = (consume_index + 1) % BUFFER_SIZE
print()
sem_post(&can_produce)
pthread_mutex_unlock(&mutex)
}
return NULL
}
int print()
{
int i
printf("Buffer:\n")
for(i = 0 i < BUFFER_SIZE i++)
printf("___")
printf("\n")
for(i = 0 i < BUFFER_SIZE i++)
printf("|%d|", buffer[i])
printf("\n")
for(i = 0 i < BUFFER_SIZE i++)
printf("___")
printf("\n")
return 0
}
如果你将mutex_c换成mutex_p,则不会死锁,因为,你第一个线程锁上后,切换到第二个线程,因为mutex_p未释放,第二个线程无法获取mutex_p,进入等待状态,此时OS将再次调度第一个线程,直到第一个线程释放mutex_p之后,第二个线程才会被激活,然后调试第二线程,获取mutex_p.使用OS提供的互斥量来保护公共资源还是比较安全的,但如果用二值信号量的话,就可能会有优先级反转的情况.
