common/worker.h

   1 /*
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  30  */
  31
  32 // Worker thread class
  33 // Used by some of the multi-threaded demos.
  34
  35 #ifndef NATIVE_CLIENT_TESTS_COMMON_WORKER_H_
  36 #define NATIVE_CLIENT_TESTS_COMMON_WORKER_H_
  37
  38 // typdef helper for pthread_create
  39 typedef void* (*Entry)(void *data);
  40
  41 // WorkerThreadManager is a class to manage N worker threads
  42 // It includes a mutex protected counter so each thread
  43 // can derive work from a uid.  It also includes two semaphores
  44 // used to synchronize the workers and the main thread.
  45
  46 class WorkerThreadManager {
  47 #if defined(HAVE_THREADS)
  48  public:
  49   void SetCounter(int v);
  50   int DecCounter();
  51   void PostWork() { sem_post(&work_); }
  52   void PostWorkAll()
  53     { for (int i = 0; i < num_threads_; ++i) sem_post(&work_); }
  54   void WaitWork() { sem_wait(&work_); }
  55   void PostDone() { sem_post(&done_); }
  56   void WaitDone() { sem_wait(&done_); }
  57   bool CreateThreadPool(int num, void *(*entry)(void *data), void *data);
  58   void JoinAll();
  59   WorkerThreadManager();
  60   ~WorkerThreadManager() { ; }
  61  private:
  62   // pthread_attr_t attr_;
  63   pthread_t *threads_;
  64   pthread_mutex_t mutex_;
  65   int counter_;
  66   int num_threads_;
  67   sem_t work_;
  68   sem_t done_;
  69 #else
  70  public:
  71   void SetCounter(int v) { ; }
  72   int DecCounter() { ; }
  73   void PostWork() { ; }
  74   void PostWorkAll() { ; }
  75   void WaitWork() { ; }
  76   void PostDone() { ; }
  77   void WaitDone() { ; }
  78   bool CreateThreadPool(int num, void *(*entry)(void *data), void *data) { ; }
  79   void JoinAll() { ; }
  80   WorkerThreadManager() { ; }
  81   ~WorkerThreadManager() { ; }
  82 #endif  // HAVE_THREADS
  83 };
  84
  85
  86 #if defined(HAVE_THREADS)
  87
  88 // Sets the mutex protected counter to specified value.
  89 inline void WorkerThreadManager::SetCounter(int v) {
  90   pthread_mutex_lock(&mutex_);
  91   { counter_ = v; }
  92   pthread_mutex_unlock(&mutex_);
  93 }
  94
  95
  96 // Decrements and get the value of the mutex protected counter
  97 inline int WorkerThreadManager::DecCounter() {
  98   int v;
  99   pthread_mutex_lock(&mutex_);
 100   { v = --counter_; }
 101   pthread_mutex_unlock(&mutex_);
 102   return v;
 103 }
 104
 105
 106 // Initializes mutex & semaphores used by worker manager.
 107 // The thread poll will be created later.
 108 inline WorkerThreadManager::WorkerThreadManager()
 109 : threads_(NULL), counter_(0), num_threads_(0) {
 110   int status;
 111   status = pthread_mutex_init(&mutex_, NULL);
 112   if (0 != status) {
 113     fprintf(stderr, "Failed to initialize mutex!\n");
 114     exit(-1);
 115   }
 116   status = sem_init(&work_, 0, 0);
 117   if (-1 == status) {
 118     fprintf(stderr, "Failed to initialize semaphore!\n");
 119     exit(-1);
 120   }
 121   status = sem_init(&done_, 0, 0);
 122   if (-1 == status) {
 123     fprintf(stderr, "Failed to initialize semaphore!\n");
 124     exit(-1);
 125   }
 126 }
 127
 128
 129 // Creates a pool of detached worker threads.
 130 inline bool WorkerThreadManager::CreateThreadPool(int num,
 131                                                   Entry entry, void *data) {
 132   if (NULL != threads_) {
 133     // shouldn't happen, but we should at least tell user
 134     fprintf(stderr, "WARNING: A thread pool has already been created!\n");
 135     return true;
 136   }
 137   // create worker threads
 138   threads_ = new pthread_t[num];
 139   num_threads_ = num;
 140   printf("Starting up %d worker threads.\n", num);
 141   for (int i = 0; i < num; ++i) {
 142     int status = pthread_create(&threads_[i], NULL, entry, data);
 143     if (0 != status) {
 144       fprintf(stderr, "Failed to allocate thread %d!\n", i);
 145       return false;
 146     }
 147   }
 148   return true;
 149 }
 150
 151
 152 // join up all the threads in the pool
 153 inline void WorkerThreadManager::JoinAll() {
 154   void *retval;
 155   for (int i = 0; i < num_threads_; ++i) {
 156     pthread_join(threads_[i], &retval);
 157   }
 158 }
 159
 160 #endif  // HAVE_THREADS
 161 #endif  // NATIVE_CLIENT_TESTS_COMMON_WORKER_H_