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POProblem with thread-safe queue?
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copied!<p>I'm trying to write a thread-safe queue using pthreads in c++. My program works 93% of the time. The other 7% of the time it other spits out garbage, OR seems to fall asleep. I'm wondering if there is some flaw in my queue where a context-switch would break it?</p> <pre><code>// thread-safe queue // inspired by http://msmvps.com/blogs/vandooren/archive/2007/01/05/creating-a-thread-safe-producer-consumer-queue-in-c-without-using-locks.aspx // only works with one producer and one consumer #include <pthread.h> #include <exception> template<class T> class tsqueue { private: volatile int m_ReadIndex, m_WriteIndex; volatile T *m_Data; volatile bool m_Done; const int m_Size; pthread_mutex_t m_ReadMutex, m_WriteMutex; pthread_cond_t m_ReadCond, m_WriteCond; public: tsqueue(const int &size); ~tsqueue(); void push(const T &elem); T pop(); void terminate(); bool isDone() const; }; template <class T> tsqueue<T>::tsqueue(const int &size) : m_ReadIndex(0), m_WriteIndex(0), m_Size(size), m_Done(false) { m_Data = new T[size]; pthread_mutex_init(&m_ReadMutex, NULL); pthread_mutex_init(&m_WriteMutex, NULL); pthread_cond_init(&m_WriteCond, NULL); pthread_cond_init(&m_WriteCond, NULL); } template <class T> tsqueue<T>::~tsqueue() { delete[] m_Data; pthread_mutex_destroy(&m_ReadMutex); pthread_mutex_destroy(&m_WriteMutex); pthread_cond_destroy(&m_ReadCond); pthread_cond_destroy(&m_WriteCond); } template <class T> void tsqueue<T>::push(const T &elem) { int next = (m_WriteIndex + 1) % m_Size; if(next == m_ReadIndex) { pthread_mutex_lock(&m_WriteMutex); pthread_cond_wait(&m_WriteCond, &m_WriteMutex); pthread_mutex_unlock(&m_WriteMutex); } m_Data[m_WriteIndex] = elem; m_WriteIndex = next; pthread_cond_signal(&m_ReadCond); } template <class T> T tsqueue<T>::pop() { if(m_ReadIndex == m_WriteIndex) { pthread_mutex_lock(&m_ReadMutex); pthread_cond_wait(&m_ReadCond, &m_ReadMutex); pthread_mutex_unlock(&m_ReadMutex); if(m_Done && m_ReadIndex == m_WriteIndex) throw "queue empty and terminated"; } int next = (m_ReadIndex +1) % m_Size; T elem = m_Data[m_ReadIndex]; m_ReadIndex = next; pthread_cond_signal(&m_WriteCond); return elem; } template <class T> void tsqueue<T>::terminate() { m_Done = true; pthread_cond_signal(&m_ReadCond); } template <class T> bool tsqueue<T>::isDone() const { return (m_Done && m_ReadIndex == m_WriteIndex); } </code></pre> <p>This could be used like this:</p> <pre><code>// thread 1 while(cin.get(c)) { queue1.push(c); } queue1.terminate(); // thread 2 while(!queue1.isDone()) { try{ c = queue1.pop(); } catch(char const* str){break;} cout.put(c); } </code></pre> <p>If anyone sees a problem with this, please say so :)</p>

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