这是在C ++中创建线程安全队列的正确方法,它可以处理二进制数据的 unsigned char * arrays 吗?
请注意,数据是从主线程生成的,而不是创建的pthread,这让我怀疑pthread_mutex_t是否会在push和pop上正常工作。
线程安全队列
#include <queue>
#include <pthread.h>
class ts_queue
{
private:
std::queue<unsigned char*> _queue_;
pthread_mutex_t mutex;
pthread_cond_t cond;
public:
ts_queue()
{
pthread_mutex_init(&mutex, NULL);
pthread_cond_init(&cond, NULL);
}
void push(unsigned char* data)
{
pthread_mutex_lock(&mutex);
_queue_.push(data);
pthread_cond_signal(&cond);
pthread_mutex_unlock(&mutex);
}
void pop(unsigned char** popped_data)
{
pthread_mutex_lock(&mutex);
while (_queue_.empty() == true)
{
pthread_cond_wait(&cond, &mutex);
}
*popped_data = _queue_.front();
_queue_.pop();
pthread_mutex_unlock(&mutex);
}
};
消费者测试:
void *consumer_thread(void *arguments)
{
ts_queue *tsq = static_cast<ts_queue*>(arguments);
while (true)
{
unsigned char* data = NULL;
tsq->pop(&data);
if (data != NULL)
{
// Eureka! Received from the other thread!!!
// Delete it so memory keeps free.
// NOTE: In the real scenario for which I need
// this class, the data received are bitmap pixels
// and at this point it would be processed
delete[] data;
}
}
return 0;
}
生产者测试:
void main()
{
ts_queue tsq;
// Create the consumer
pthread_t consumer;
pthread_create(&consumer, NULL, consumer_thread, &tsq));
// Start producing
while(true)
{
// Push data.
// Expected behaviour: memory should never run out, as the
// consumer should receive the data and delete it.
// NOTE: test_data in the real purpose scenario for which I
// need this class would hold bitmap pixels, so it's meant to
// hold binary data and not a string
unsigned char* test_data = new unsigned char [8192];
tsq.push(test_data);
}
return 0;
}
答案 0 :(得分:1)
您如何知道消费者永远不会获得数据?当我尝试你的程序时,我得到一个分段错误,GDB告诉我消费者确实得到了一个指针,但它是一个无效的。
我相信您的问题是您在_queue_
成员上进行了数据竞争。在push()
和_queue_.push(data)
来电_queue_
时,push_mutex
拨打pop()
(写在_queue_.front()
上)(阅读_queue_
)并且_queue_.pop()
(另一个写在_queue_
上)同时持有pop_mutex
,但push()
和pop()
可以同时发生,导致两个线程都在写(和阅读)_queue_
同时是一个经典的数据竞赛。