/src/FreeImage/Source/OpenEXR/IlmThread/IlmThreadPool.cpp

  1///////////////////////////////////////////////////////////////////////////
  2//
  3// Copyright (c) 2005, Industrial Light & Magic, a division of Lucas
  4// Digital Ltd. LLC
  5// 
  6// All rights reserved.
  7// 
  8// Redistribution and use in source and binary forms, with or without
  9// modification, are permitted provided that the following conditions are
 10// met:
 11// *       Redistributions of source code must retain the above copyright
 12// notice, this list of conditions and the following disclaimer.
 13// *       Redistributions in binary form must reproduce the above
 14// copyright notice, this list of conditions and the following disclaimer
 15// in the documentation and/or other materials provided with the
 16// distribution.
 17// *       Neither the name of Industrial Light & Magic nor the names of
 18// its contributors may be used to endorse or promote products derived
 19// from this software without specific prior written permission. 
 20// 
 21// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 22// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 23// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 24// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 25// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 26// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 27// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 28// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 29// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 30// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 31// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 32//
 33///////////////////////////////////////////////////////////////////////////
 34
 35//-----------------------------------------------------------------------------
 36//
 37//	class Task, class ThreadPool, class TaskGroup
 38//
 39//-----------------------------------------------------------------------------
 40
 41#include "IlmThread.h"
 42#include "IlmThreadMutex.h"
 43#include "IlmThreadSemaphore.h"
 44#include "IlmThreadPool.h"
 45#include "Iex.h"
 46#include <list>
 47
 48using namespace std;
 49
 50namespace IlmThread {
 51namespace {
 52
 53class WorkerThread: public Thread
 54{
 55  public:
 56
 57    WorkerThread (ThreadPool::Data* data);
 58
 59    virtual void	run ();
 60    
 61  private:
 62
 63    ThreadPool::Data *	_data;
 64};
 65
 66} //namespace
 67
 68
 69struct TaskGroup::Data
 70{
 71     Data ();
 72    ~Data ();
 73    
 74    void	addTask () ;
 75    void	removeTask ();
 76    
 77    Semaphore	isEmpty;	// used to signal that the taskgroup is empty
 78    int		numPending;	// number of pending tasks to still execute
 79};
 80
 81
 82struct ThreadPool::Data
 83{
 84     Data ();
 85    ~Data();
 86    
 87    void	finish ();
 88    bool	stopped () const;
 89    void	stop ();
 90
 91    Semaphore taskSemaphore;        // threads wait on this for ready tasks
 92    Mutex taskMutex;                // mutual exclusion for the tasks list
 93    list<Task*> tasks;              // the list of tasks to execute
 94    size_t numTasks;                // fast access to list size
 95                                    //   (list::size() can be O(n))
 96
 97    Semaphore threadSemaphore;      // signaled when a thread starts executing
 98    Mutex threadMutex;              // mutual exclusion for threads list
 99    list<WorkerThread*> threads;    // the list of all threads
100    size_t numThreads;              // fast access to list size
101    
102    bool stopping;                  // flag indicating whether to stop threads
103    Mutex stopMutex;                // mutual exclusion for stopping flag
104};
105
106
107
108//
109// class WorkerThread
110//
111
112WorkerThread::WorkerThread (ThreadPool::Data* data):
113    _data (data)
114{
115    start();
116}
117
118
119void
120WorkerThread::run ()
121{
122    //
123    // Signal that the thread has started executing
124    //
125
126    _data->threadSemaphore.post();
127
128    while (true)
129    {
130	//
131        // Wait for a task to become available
132	//
133
134        _data->taskSemaphore.wait();
135
136        {
137            Lock taskLock (_data->taskMutex);
138    
139	    //
140            // If there is a task pending, pop off the next task in the FIFO
141	    //
142
143            if (_data->numTasks > 0)
144            {
145                Task* task = _data->tasks.front();
146		TaskGroup* taskGroup = task->group();
147                _data->tasks.pop_front();
148                _data->numTasks--;
149
150                taskLock.release();
151                task->execute();
152                taskLock.acquire();
153
154                delete task;
155                taskGroup->_data->removeTask();
156            }
157            else if (_data->stopped())
158	    {
159                break;
160	    }
161        }
162    }
163}
164
165
166//
167// struct TaskGroup::Data
168//
169
170TaskGroup::Data::Data (): isEmpty (1), numPending (0)
171{
172    // empty
173}
174
175
176TaskGroup::Data::~Data ()
177{
178    //
179    // A TaskGroup acts like an "inverted" semaphore: if the count
180    // is above 0 then waiting on the taskgroup will block.  This
181    // destructor waits until the taskgroup is empty before returning.
182    //
183
184    isEmpty.wait ();
185}
186
187
188void
189TaskGroup::Data::addTask () 
190{
191    //
192    // Any access to the taskgroup is protected by a mutex that is
193    // held by the threadpool.  Therefore it is safe to access
194    // numPending before we wait on the semaphore.
195    //
196
197    if (numPending++ == 0)
198	isEmpty.wait ();
199}
200
201
202void
203TaskGroup::Data::removeTask ()
204{
205    if (--numPending == 0)
206	isEmpty.post ();
207}
208    
209
210//
211// struct ThreadPool::Data
212//
213
214ThreadPool::Data::Data (): numTasks (0), numThreads (0), stopping (false)
215{
216    // empty
217}
218
219
220ThreadPool::Data::~Data()
221{
222    Lock lock (threadMutex);
223    finish ();
224}
225
226
227void
228ThreadPool::Data::finish ()
229{
230    stop();
231
232    //
233    // Signal enough times to allow all threads to stop.
234    //
235    // Wait until all threads have started their run functions.
236    // If we do not wait before we destroy the threads then it's
237    // possible that the threads have not yet called their run
238    // functions.
239    // If this happens then the run function will be called off
240    // of an invalid object and we will crash, most likely with
241    // an error like: "pure virtual method called"
242    //
243
244    for (size_t i = 0; i < numThreads; i++)
245    {
246	taskSemaphore.post();
247	threadSemaphore.wait();
248    }
249
250    //
251    // Join all the threads
252    //
253
254    for (list<WorkerThread*>::iterator i = threads.begin();
255	 i != threads.end();
256	 ++i)
257    {
258	delete (*i);
259    }
260
261    Lock lock1 (taskMutex);
262    Lock lock2 (stopMutex);
263    threads.clear();
264    tasks.clear();
265    numThreads = 0;
266    numTasks = 0;
267    stopping = false;
268}
269
270
271bool
272ThreadPool::Data::stopped () const
273{
274    Lock lock (stopMutex);
275    return stopping;
276}
277
278
279void
280ThreadPool::Data::stop ()
281{
282    Lock lock (stopMutex);
283    stopping = true;
284}
285
286
287//
288// class Task
289//
290
291Task::Task (TaskGroup* g): _group(g)
292{
293    // empty
294}
295
296
297Task::~Task()
298{
299    // empty
300}
301
302
303TaskGroup*
304Task::group ()
305{
306    return _group;
307}
308
309
310TaskGroup::TaskGroup ():
311    _data (new Data())
312{
313    // empty
314}
315
316
317TaskGroup::~TaskGroup ()
318{
319    delete _data;
320}
321
322
323//
324// class ThreadPool
325//
326
327ThreadPool::ThreadPool (unsigned nthreads):
328    _data (new Data())
329{
330    setNumThreads (nthreads);
331}
332
333
334ThreadPool::~ThreadPool ()
335{
336    delete _data;
337}
338
339
340int
341ThreadPool::numThreads () const
342{
343    Lock lock (_data->threadMutex);
344    return _data->numThreads;
345}
346
347
348void
349ThreadPool::setNumThreads (int count)
350{
351    if (count < 0)
352        throw Iex::ArgExc ("Attempt to set the number of threads "
353			   "in a thread pool to a negative value.");
354
355    //
356    // Lock access to thread list and size
357    //
358
359    Lock lock (_data->threadMutex);
360
361    if ((size_t)count > _data->numThreads)
362    {
363	//
364        // Add more threads
365	//
366
367        while (_data->numThreads < (size_t)count)
368        {
369            _data->threads.push_back (new WorkerThread (_data));
370            _data->numThreads++;
371        }
372    }
373    else if ((size_t)count < _data->numThreads)
374    {
375	//
376	// Wait until all existing threads are finished processing,
377	// then delete all threads.
378	//
379
380        _data->finish ();
381
382	//
383        // Add in new threads
384	//
385
386        while (_data->numThreads < (size_t)count)
387        {
388            _data->threads.push_back (new WorkerThread (_data));
389            _data->numThreads++;
390        }
391    }
392}
393
394
395void
396ThreadPool::addTask (Task* task) 
397{
398    //
399    // Lock the threads, needed to access numThreads
400    //
401
402    Lock lock (_data->threadMutex);
403
404    if (_data->numThreads == 0)
405    {
406        task->execute ();
407        delete task;
408    }
409    else
410    {
411	//
412        // Get exclusive access to the tasks queue
413	//
414
415        {
416            Lock taskLock (_data->taskMutex);
417
418	    //
419            // Push the new task into the FIFO
420	    //
421
422            _data->tasks.push_back (task);
423            _data->numTasks++;
424            task->group()->_data->addTask();
425        }
426        
427	//
428        // Signal that we have a new task to process
429	//
430
431        _data->taskSemaphore.post ();
432    }
433}
434
435
436ThreadPool&
437ThreadPool::globalThreadPool ()
438{
439    //
440    // The global thread pool
441    //
442    
443    static ThreadPool gThreadPool (0);
444
445    return gThreadPool;
446}
447
448
449void
450ThreadPool::addGlobalTask (Task* task)
451{
452    globalThreadPool().addTask (task);
453}
454
455
456} // namespace IlmThread