您需要的是条件变量。
所有工作线程都调用wait（），这将暂停它们。
然后，父线程将工作项放在队列中，并在条件变量上调用signal。这将唤醒正在hibernate的一个线程。它可以从队列中删除该作业，然后执行该作业，然后在条件变量上调用wait以返回睡眠状态。
尝试：
#include <pthread.h>#include <memory>#include <list>// Use RAII to do the lock/unlockstruct MutexLock{ MutexLock(pthread_mutex_t& m) : mutex(m) { pthread_mutex_lock(&mutex); } ~MutexLock() { pthread_mutex_unlock(&mutex); } private: pthread_mutex_t& mutex;};// The base class of all work we want to do.struct Job{ virtual void doWork() = 0;};// pthreads is a C library the call back must be a C function.extern "C" void* threadPoolThreadStart(void*);// The very basre minimal part of a thread pool// It does not create the workers. You need to create the work threads// then make them call workerStart(). I leave that as an exercise for you.class ThreadPool{ public: ThreadPool(unsigned int threadCount=1); ~ThreadPool(); void addWork(std::auto_ptr<Job> job); private: friend void* threadPoolThreadStart(void*); void workerStart(); std::auto_ptr<Job> getJob(); bool finished; // Threads will re-wait while this is true. pthread_mutex_t mutex; // A lock so that we can sequence accesses. pthread_cond_t cond; // The condition variable that is used to hold worker threads. std::list<Job*> workQueue; // A queue of jobs. std::vector<pthread_t>threads;};// Create the thread poolThreadPool::ThreadPool(int unsigned threadCount) : finished(false) , threads(threadCount){ // If we fail creating either pthread object than throw a fit. if (pthread_mutex_init(&mutex, NULL) != 0) { throw int(1); } if (pthread_cond_init(&cond, NULL) != 0) { pthread_mutex_destroy(&mutex); throw int(2); } for(unsigned int loop=0; loop < threadCount;++loop) { if (pthread_create(threads[loop], NULL, threadPoolThreadStart, this) != 0) { // One thread failed: clean up for(unsigned int kill = loop -1; kill < loop ;--kill) { pthread_kill(threads[kill], 9); } throw int(3); } }}// Cleanup any left overs.// Note. This does not deal with worker threads.// You need to add a method to flush all worker threads// out of this pobject before you let the destructor destroy it.ThreadPool::~ThreadPool(){ finished = true; for(std::vector<pthread_t>::iterator loop = threads.begin();loop != threads.end(); ++loop) { // Send enough signals to free all threads. pthread_cond_signal(&cond); } for(std::vector<pthread_t>::iterator loop = threads.begin();loop != threads.end(); ++loop) { // Wait for all threads to exit (they will as finished is true and // we sent enough signals to make sure // they are running). void* result; pthread_join(*loop, &result); } // Destroy the pthread objects. pthread_cond_destroy(&cond); pthread_mutex_destroy(&mutex); // Delete all re-maining jobs. // Notice how we took ownership of the jobs. for(std::list<Job*>::const_iterator loop = workQueue.begin(); loop != workQueue.end();++loop) { delete *loop; }}// Add a new job to the queue// Signal the condition variable. This will flush a waiting worker// otherwise the job will wait for a worker to finish processing its current job.void ThreadPool::addWork(std::auto_ptr<Job> job){ MutexLock lock(mutex); workQueue.push_back(job.release()); pthread_cond_signal(&cond);}// Start a thread.// Make sure no exceptions escape as that is bad.void* threadPoolThreadStart(void* data){ ThreadPool* pool = reinterpret_cast<ThreadPool*>(workerStart); try { pool->workerStart(); } catch(...){} return NULL;}// This is the main worker loop.void ThreadPool::workerStart(){ while(!finished) { std::auto_ptr<Job> job = getJob(); if (job.get() != NULL) { job->doWork(); } }}// The workers come here to get a job.// If there are non in the queue they are suspended waiting on cond// until a new job is added above.std::auto_ptr<Job> ThreadPool::getJob(){ MutexLock lock(mutex); while((workQueue.empty()) && (!finished)) { pthread_cond_wait(&cond, &mutex); // The wait releases the mutex lock and suspends the thread (until a signal). // When a thread wakes up it is help until it can acquire the mutex so when we // get here the mutex is again locked. // // Note: You must use while() here. This is because of the situation. // Two workers: Worker A processing job A. // Worker B suspended on condition variable. // Parent adds a new job and calls signal. // This wakes up thread B. But it is possible for Worker A to finish its // work and lock the mutex before the Worker B is released from the above call. // // If that happens then Worker A will see that the queue is not empty // and grab the work item in the queue and start processing. Worker B will // then lock the mutext and proceed here. If the above is not a while then // it would try and remove an item from an empty queue. With a while it sees // that the queue is empty and re-suspends on the condition variable above. } std::auto_ptr<Job> result; if (!finished) { result.reset(workQueue.front()); workQueue.pop_front(); } return result;}
