summaryrefslogtreecommitdiffstats
path: root/base/condition_variable_unittest.cc
blob: 95756e0c96468031c8f5bc94b802ac002c5aa3a2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Multi-threaded tests of ConditionVariable class.

#include <time.h>
#include <algorithm>
#include <vector>

#include "base/condition_variable.h"
#include "base/lock.h"
#include "base/logging.h"
#include "base/platform_thread.h"
#include "base/scoped_ptr.h"
#include "base/spin_wait.h"
#include "base/thread_collision_warner.h"
#include "base/time.h"
#include "testing/gtest/include/gtest/gtest.h"
#include "testing/platform_test.h"

using base::TimeDelta;
using base::TimeTicks;

namespace {
//------------------------------------------------------------------------------
// Define our test class, with several common variables.
//------------------------------------------------------------------------------

class ConditionVariableTest : public PlatformTest {
 public:
  const TimeDelta kZeroMs;
  const TimeDelta kTenMs;
  const TimeDelta kThirtyMs;
  const TimeDelta kFortyFiveMs;
  const TimeDelta kSixtyMs;
  const TimeDelta kOneHundredMs;

  explicit ConditionVariableTest()
    : kZeroMs(TimeDelta::FromMilliseconds(0)),
      kTenMs(TimeDelta::FromMilliseconds(10)),
      kThirtyMs(TimeDelta::FromMilliseconds(30)),
      kFortyFiveMs(TimeDelta::FromMilliseconds(45)),
      kSixtyMs(TimeDelta::FromMilliseconds(60)),
      kOneHundredMs(TimeDelta::FromMilliseconds(100)) {
  }
};

//------------------------------------------------------------------------------
// Define a class that will control activities an several multi-threaded tests.
// The general structure of multi-threaded tests is that a test case will
// construct an instance of a WorkQueue.  The WorkQueue will spin up some
// threads and control them throughout their lifetime, as well as maintaining
// a central repository of the work thread's activity.  Finally, the WorkQueue
// will command the the worker threads to terminate.  At that point, the test
// cases will validate that the WorkQueue has records showing that the desired
// activities were performed.
//------------------------------------------------------------------------------

// Callers are responsible for synchronizing access to the following class.
// The WorkQueue::lock_, as accessed via WorkQueue::lock(), should be used for
// all synchronized access.
class WorkQueue : public PlatformThread::Delegate {
 public:
  explicit WorkQueue(int thread_count);
  ~WorkQueue();

  // PlatformThread::Delegate interface.
  void ThreadMain();

  //----------------------------------------------------------------------------
  // Worker threads only call the following methods.
  // They should use the lock to get exclusive access.
  int GetThreadId();  // Get an ID assigned to a thread..
  bool EveryIdWasAllocated() const;  // Indicates that all IDs were handed out.
  TimeDelta GetAnAssignment(int thread_id);  // Get a work task duration.
  void WorkIsCompleted(int thread_id);

  int task_count() const;
  bool allow_help_requests() const;  // Workers can signal more workers.
  bool shutdown() const;  // Check if shutdown has been requested.

  void thread_shutting_down();


  //----------------------------------------------------------------------------
  // Worker threads can call them but not needed to acquire a lock.
  Lock* lock();

  ConditionVariable* work_is_available();
  ConditionVariable* all_threads_have_ids();
  ConditionVariable* no_more_tasks();

  //----------------------------------------------------------------------------
  // The rest of the methods are for use by the controlling master thread (the
  // test case code).
  void ResetHistory();
  int GetMinCompletionsByWorkerThread() const;
  int GetMaxCompletionsByWorkerThread() const;
  int GetNumThreadsTakingAssignments() const;
  int GetNumThreadsCompletingTasks() const;
  int GetNumberOfCompletedTasks() const;
  TimeDelta GetWorkTime() const;

  void SetWorkTime(TimeDelta delay);
  void SetTaskCount(int count);
  void SetAllowHelp(bool allow);

  // Caller must acquire lock before calling.
  void SetShutdown();

  // Compares the |shutdown_task_count_| to the |thread_count| and returns true
  // if they are equal.  This check will acquire the |lock_| so the caller
  // should not hold the lock when calling this method.
  bool ThreadSafeCheckShutdown(int thread_count);

 private:
  // Both worker threads and controller use the following to synchronize.
  Lock lock_;
  ConditionVariable work_is_available_;  // To tell threads there is work.

  // Conditions to notify the controlling process (if it is interested).
  ConditionVariable all_threads_have_ids_;  // All threads are running.
  ConditionVariable no_more_tasks_;  // Task count is zero.

  const int thread_count_;
  scoped_array<PlatformThreadHandle> thread_handles_;
  std::vector<int> assignment_history_;  // Number of assignment per worker.
  std::vector<int> completion_history_;  // Number of completions per worker.
  int thread_started_counter_;  // Used to issue unique id to workers.
  int shutdown_task_count_;  // Number of tasks told to shutdown
  int task_count_;  // Number of assignment tasks waiting to be processed.
  TimeDelta worker_delay_;  // Time each task takes to complete.
  bool allow_help_requests_;  // Workers can signal more workers.
  bool shutdown_;  // Set when threads need to terminate.

  DFAKE_MUTEX(locked_methods_);
};

//------------------------------------------------------------------------------
// The next section contains the actual tests.
//------------------------------------------------------------------------------

TEST_F(ConditionVariableTest, StartupShutdownTest) {
  Lock lock;

  // First try trivial startup/shutdown.
  {
    ConditionVariable cv1(&lock);
  }  // Call for cv1 destruction.

  // Exercise with at least a few waits.
  ConditionVariable cv(&lock);

  lock.Acquire();
  cv.TimedWait(kTenMs);  // Wait for 10 ms.
  cv.TimedWait(kTenMs);  // Wait for 10 ms.
  lock.Release();

  lock.Acquire();
  cv.TimedWait(kTenMs);  // Wait for 10 ms.
  cv.TimedWait(kTenMs);  // Wait for 10 ms.
  cv.TimedWait(kTenMs);  // Wait for 10 ms.
  lock.Release();
}  // Call for cv destruction.

TEST_F(ConditionVariableTest, TimeoutTest) {
  Lock lock;
  ConditionVariable cv(&lock);
  lock.Acquire();

  TimeTicks start = TimeTicks::Now();
  const TimeDelta WAIT_TIME = TimeDelta::FromMilliseconds(300);
  // Allow for clocking rate granularity.
  const TimeDelta FUDGE_TIME = TimeDelta::FromMilliseconds(50);

  cv.TimedWait(WAIT_TIME + FUDGE_TIME);
  TimeDelta duration = TimeTicks::Now() - start;
  // We can't use EXPECT_GE here as the TimeDelta class does not support the
  // required stream conversion.
  EXPECT_TRUE(duration >= WAIT_TIME);

  lock.Release();
}

// Test serial task servicing, as well as two parallel task servicing methods.
// TODO(maruel): This test is flaky, see http://crbug.com/10607
TEST_F(ConditionVariableTest, FLAKY_MultiThreadConsumerTest) {
  const int kThreadCount = 10;
  WorkQueue queue(kThreadCount);  // Start the threads.

  const int kTaskCount = 10;  // Number of tasks in each mini-test here.

  base::Time start_time;  // Used to time task processing.

  {
    AutoLock auto_lock(*queue.lock());
    while (!queue.EveryIdWasAllocated())
      queue.all_threads_have_ids()->Wait();
  }

  // Wait a bit more to allow threads to reach their wait state.
  // If threads aren't in a wait state, they may start to gobble up tasks in
  // parallel, short-circuiting (breaking) this test.
  PlatformThread::Sleep(100);

  {
    // Since we have no tasks yet, all threads should be waiting by now.
    AutoLock auto_lock(*queue.lock());
    EXPECT_EQ(0, queue.GetNumThreadsTakingAssignments());
    EXPECT_EQ(0, queue.GetNumThreadsCompletingTasks());
    EXPECT_EQ(0, queue.task_count());
    EXPECT_EQ(0, queue.GetMaxCompletionsByWorkerThread());
    EXPECT_EQ(0, queue.GetMinCompletionsByWorkerThread());
    EXPECT_EQ(0, queue.GetNumberOfCompletedTasks());

    // Set up to make one worker do 30ms tasks sequentially.
    queue.ResetHistory();
    queue.SetTaskCount(kTaskCount);
    queue.SetWorkTime(kThirtyMs);
    queue.SetAllowHelp(false);

    start_time = base::Time::Now();
  }

  queue.work_is_available()->Signal();  // Start up one thread.


  {
    // Wait until all 10 work tasks have at least been assigned.
    AutoLock auto_lock(*queue.lock());
    while (queue.task_count())
      queue.no_more_tasks()->Wait();
    // The last of the tasks *might* still be running, but... all but one should
    // be done by now, since tasks are being done serially.
    EXPECT_LE(queue.GetWorkTime().InMilliseconds() * (kTaskCount - 1),
              (base::Time::Now() - start_time).InMilliseconds());

    EXPECT_EQ(1, queue.GetNumThreadsTakingAssignments());
    EXPECT_EQ(1, queue.GetNumThreadsCompletingTasks());
    EXPECT_LE(kTaskCount - 1, queue.GetMaxCompletionsByWorkerThread());
    EXPECT_EQ(0, queue.GetMinCompletionsByWorkerThread());
    EXPECT_LE(kTaskCount - 1, queue.GetNumberOfCompletedTasks());
  }

  // Wait to be sure all tasks are done.
  while (1) {
    {
      AutoLock auto_lock(*queue.lock());
      if (kTaskCount == queue.GetNumberOfCompletedTasks())
        break;
    }
    PlatformThread::Sleep(30);  // Wait a little.
  }

  {
    // Check that all work was done by one thread id.
    AutoLock auto_lock(*queue.lock());
    EXPECT_EQ(1, queue.GetNumThreadsTakingAssignments());
    EXPECT_EQ(1, queue.GetNumThreadsCompletingTasks());
    EXPECT_EQ(0, queue.task_count());
    EXPECT_EQ(kTaskCount, queue.GetMaxCompletionsByWorkerThread());
    EXPECT_EQ(0, queue.GetMinCompletionsByWorkerThread());
    EXPECT_EQ(kTaskCount, queue.GetNumberOfCompletedTasks());

    // Set up to make each task include getting help from another worker, so
    // so that the work gets done in paralell.
    queue.ResetHistory();
    queue.SetTaskCount(kTaskCount);
    queue.SetWorkTime(kThirtyMs);
    queue.SetAllowHelp(true);

    start_time = base::Time::Now();
  }

  queue.work_is_available()->Signal();  // But each worker can signal another.
  // Wait to allow the all workers to get done.
  while (1) {
    {
      AutoLock auto_lock(*queue.lock());
      if (kTaskCount == queue.GetNumberOfCompletedTasks())
        break;
    }
    PlatformThread::Sleep(30);  // Wait a little.
  }

  {
    // Wait until all work tasks have at least been assigned.
    AutoLock auto_lock(*queue.lock());
    while (queue.task_count())
      queue.no_more_tasks()->Wait();
    // Since they can all run almost in parallel, there is no guarantee that all
    // tasks are finished, but we should have gotten here faster than it would
    // take to run all tasks serially.
    EXPECT_GT(queue.GetWorkTime().InMilliseconds() * (kTaskCount - 1),
              (base::Time::Now() - start_time).InMilliseconds());

    // To avoid racy assumptions, we'll just assert that at least 2 threads
    // did work.
    EXPECT_LE(2, queue.GetNumThreadsTakingAssignments());
    EXPECT_EQ(kTaskCount, queue.GetNumberOfCompletedTasks());

    // Try to ask all workers to help, and only a few will do the work.
    queue.ResetHistory();
    queue.SetTaskCount(3);
    queue.SetWorkTime(kThirtyMs);
    queue.SetAllowHelp(false);
  }
  queue.work_is_available()->Broadcast();  // Make them all try.
  // Wait to allow the 3 workers to get done.
  PlatformThread::Sleep(45);

  {
    AutoLock auto_lock(*queue.lock());
    EXPECT_EQ(3, queue.GetNumThreadsTakingAssignments());
    EXPECT_EQ(3, queue.GetNumThreadsCompletingTasks());
    EXPECT_EQ(0, queue.task_count());
    EXPECT_EQ(1, queue.GetMaxCompletionsByWorkerThread());
    EXPECT_EQ(0, queue.GetMinCompletionsByWorkerThread());
    EXPECT_EQ(3, queue.GetNumberOfCompletedTasks());

    // Set up to make each task get help from another worker.
    queue.ResetHistory();
    queue.SetTaskCount(3);
    queue.SetWorkTime(kThirtyMs);
    queue.SetAllowHelp(true);  // Allow (unnecessary) help requests.
  }
  queue.work_is_available()->Broadcast();  // We already signal all threads.
  // Wait to allow the 3 workers to get done.
  PlatformThread::Sleep(100);

  {
    AutoLock auto_lock(*queue.lock());
    EXPECT_EQ(3, queue.GetNumThreadsTakingAssignments());
    EXPECT_EQ(3, queue.GetNumThreadsCompletingTasks());
    EXPECT_EQ(0, queue.task_count());
    EXPECT_EQ(1, queue.GetMaxCompletionsByWorkerThread());
    EXPECT_EQ(0, queue.GetMinCompletionsByWorkerThread());
    EXPECT_EQ(3, queue.GetNumberOfCompletedTasks());

    // Set up to make each task get help from another worker.
    queue.ResetHistory();
    queue.SetTaskCount(20);
    queue.SetWorkTime(kThirtyMs);
    queue.SetAllowHelp(true);
  }
  queue.work_is_available()->Signal();  // But each worker can signal another.
  // Wait to allow the 10 workers to get done.
  PlatformThread::Sleep(100);  // Should take about 60 ms.

  {
    AutoLock auto_lock(*queue.lock());
    EXPECT_EQ(10, queue.GetNumThreadsTakingAssignments());
    EXPECT_EQ(10, queue.GetNumThreadsCompletingTasks());
    EXPECT_EQ(0, queue.task_count());
    EXPECT_EQ(2, queue.GetMaxCompletionsByWorkerThread());
    EXPECT_EQ(2, queue.GetMinCompletionsByWorkerThread());
    EXPECT_EQ(20, queue.GetNumberOfCompletedTasks());

    // Same as last test, but with Broadcast().
    queue.ResetHistory();
    queue.SetTaskCount(20);  // 2 tasks per process.
    queue.SetWorkTime(kThirtyMs);
    queue.SetAllowHelp(true);
  }
  queue.work_is_available()->Broadcast();
  // Wait to allow the 10 workers to get done.
  PlatformThread::Sleep(100);  // Should take about 60 ms.

  {
    AutoLock auto_lock(*queue.lock());
    EXPECT_EQ(10, queue.GetNumThreadsTakingAssignments());
    EXPECT_EQ(10, queue.GetNumThreadsCompletingTasks());
    EXPECT_EQ(0, queue.task_count());
    EXPECT_EQ(2, queue.GetMaxCompletionsByWorkerThread());
    EXPECT_EQ(2, queue.GetMinCompletionsByWorkerThread());
    EXPECT_EQ(20, queue.GetNumberOfCompletedTasks());

    queue.SetShutdown();
  }
  queue.work_is_available()->Broadcast();  // Force check for shutdown.

  SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(TimeDelta::FromMinutes(1),
                                   queue.ThreadSafeCheckShutdown(kThreadCount));
  PlatformThread::Sleep(10);  // Be sure they're all shutdown.
}

TEST_F(ConditionVariableTest, LargeFastTaskTest) {
  const int kThreadCount = 200;
  WorkQueue queue(kThreadCount);  // Start the threads.

  Lock private_lock;  // Used locally for master to wait.
  AutoLock private_held_lock(private_lock);
  ConditionVariable private_cv(&private_lock);

  {
    AutoLock auto_lock(*queue.lock());
    while (!queue.EveryIdWasAllocated())
      queue.all_threads_have_ids()->Wait();
  }

  // Wait a bit more to allow threads to reach their wait state.
  private_cv.TimedWait(kThirtyMs);

  {
    // Since we have no tasks, all threads should be waiting by now.
    AutoLock auto_lock(*queue.lock());
    EXPECT_EQ(0, queue.GetNumThreadsTakingAssignments());
    EXPECT_EQ(0, queue.GetNumThreadsCompletingTasks());
    EXPECT_EQ(0, queue.task_count());
    EXPECT_EQ(0, queue.GetMaxCompletionsByWorkerThread());
    EXPECT_EQ(0, queue.GetMinCompletionsByWorkerThread());
    EXPECT_EQ(0, queue.GetNumberOfCompletedTasks());

    // Set up to make all workers do (an average of) 20 tasks.
    queue.ResetHistory();
    queue.SetTaskCount(20 * kThreadCount);
    queue.SetWorkTime(kFortyFiveMs);
    queue.SetAllowHelp(false);
  }
  queue.work_is_available()->Broadcast();  // Start up all threads.
  // Wait until we've handed out all tasks.
  {
    AutoLock auto_lock(*queue.lock());
    while (queue.task_count() != 0)
      queue.no_more_tasks()->Wait();
  }

  // Wait till the last of the tasks complete.
  // Don't bother to use locks: We may not get info in time... but we'll see it
  // eventually.
  SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(TimeDelta::FromMinutes(1),
                                    20 * kThreadCount ==
                                      queue.GetNumberOfCompletedTasks());

  {
    // With Broadcast(), every thread should have participated.
    // but with racing.. they may not all have done equal numbers of tasks.
    AutoLock auto_lock(*queue.lock());
    EXPECT_EQ(kThreadCount, queue.GetNumThreadsTakingAssignments());
    EXPECT_EQ(kThreadCount, queue.GetNumThreadsCompletingTasks());
    EXPECT_EQ(0, queue.task_count());
    EXPECT_LE(20, queue.GetMaxCompletionsByWorkerThread());
    EXPECT_EQ(20 * kThreadCount, queue.GetNumberOfCompletedTasks());

    // Set up to make all workers do (an average of) 4 tasks.
    queue.ResetHistory();
    queue.SetTaskCount(kThreadCount * 4);
    queue.SetWorkTime(kFortyFiveMs);
    queue.SetAllowHelp(true);  // Might outperform Broadcast().
  }
  queue.work_is_available()->Signal();  // Start up one thread.

  // Wait until we've handed out all tasks
  {
    AutoLock auto_lock(*queue.lock());
    while (queue.task_count() != 0)
      queue.no_more_tasks()->Wait();
  }

  // Wait till the last of the tasks complete.
  // Don't bother to use locks: We may not get info in time... but we'll see it
  // eventually.
  SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(TimeDelta::FromMinutes(1),
                                    4 * kThreadCount ==
                                      queue.GetNumberOfCompletedTasks());

  {
    // With Signal(), every thread should have participated.
    // but with racing.. they may not all have done four tasks.
    AutoLock auto_lock(*queue.lock());
    EXPECT_EQ(kThreadCount, queue.GetNumThreadsTakingAssignments());
    EXPECT_EQ(kThreadCount, queue.GetNumThreadsCompletingTasks());
    EXPECT_EQ(0, queue.task_count());
    EXPECT_LE(4, queue.GetMaxCompletionsByWorkerThread());
    EXPECT_EQ(4 * kThreadCount, queue.GetNumberOfCompletedTasks());

    queue.SetShutdown();
  }
  queue.work_is_available()->Broadcast();  // Force check for shutdown.

  // Wait for shutdowns to complete.
  SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(TimeDelta::FromMinutes(1),
                                   queue.ThreadSafeCheckShutdown(kThreadCount));
  PlatformThread::Sleep(10);  // Be sure they're all shutdown.
}

//------------------------------------------------------------------------------
// Finally we provide the implementation for the methods in the WorkQueue class.
//------------------------------------------------------------------------------

WorkQueue::WorkQueue(int thread_count)
  : lock_(),
    work_is_available_(&lock_),
    all_threads_have_ids_(&lock_),
    no_more_tasks_(&lock_),
    thread_count_(thread_count),
    thread_handles_(new PlatformThreadHandle[thread_count]),
    assignment_history_(thread_count),
    completion_history_(thread_count),
    thread_started_counter_(0),
    shutdown_task_count_(0),
    task_count_(0),
    allow_help_requests_(false),
    shutdown_(false) {
  EXPECT_GE(thread_count_, 1);
  ResetHistory();
  SetTaskCount(0);
  SetWorkTime(TimeDelta::FromMilliseconds(30));

  for (int i = 0; i < thread_count_; ++i) {
    PlatformThreadHandle pth;
    EXPECT_TRUE(PlatformThread::Create(0, this, &pth));
    thread_handles_[i] = pth;
  }
}

WorkQueue::~WorkQueue() {
  {
    AutoLock auto_lock(lock_);
    SetShutdown();
  }
  work_is_available_.Broadcast();  // Tell them all to terminate.

  for (int i = 0; i < thread_count_; ++i) {
    PlatformThread::Join(thread_handles_[i]);
  }
}

int WorkQueue::GetThreadId() {
  DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
  DCHECK(!EveryIdWasAllocated());
  return thread_started_counter_++;  // Give out Unique IDs.
}

bool WorkQueue::EveryIdWasAllocated() const {
  DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
  return thread_count_ == thread_started_counter_;
}

TimeDelta WorkQueue::GetAnAssignment(int thread_id) {
  DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
  DCHECK_LT(0, task_count_);
  assignment_history_[thread_id]++;
  if (0 == --task_count_) {
    no_more_tasks_.Signal();
  }
  return worker_delay_;
}

void WorkQueue::WorkIsCompleted(int thread_id) {
  DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
  completion_history_[thread_id]++;
}

int WorkQueue::task_count() const {
  DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
  return task_count_;
}

bool WorkQueue::allow_help_requests() const {
  DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
  return allow_help_requests_;
}

bool WorkQueue::shutdown() const {
  lock_.AssertAcquired();
  DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
  return shutdown_;
}

// Because this method is called from the test's main thread we need to actually
// take the lock.  Threads will call the thread_shutting_down() method with the
// lock already acquired.
bool WorkQueue::ThreadSafeCheckShutdown(int thread_count) {
  bool all_shutdown;
  AutoLock auto_lock(lock_);
  {
    // Declare in scope so DFAKE is guranteed to be destroyed before AutoLock.
    DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
    all_shutdown = (shutdown_task_count_ == thread_count);
  }
  return all_shutdown;
}

void WorkQueue::thread_shutting_down() {
  lock_.AssertAcquired();
  DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
  shutdown_task_count_++;
}

Lock* WorkQueue::lock() {
  return &lock_;
}

ConditionVariable* WorkQueue::work_is_available() {
  return &work_is_available_;
}

ConditionVariable* WorkQueue::all_threads_have_ids() {
  return &all_threads_have_ids_;
}

ConditionVariable* WorkQueue::no_more_tasks() {
  return &no_more_tasks_;
}

void WorkQueue::ResetHistory() {
  for (int i = 0; i < thread_count_; ++i) {
    assignment_history_[i] = 0;
    completion_history_[i] = 0;
  }
}

int WorkQueue::GetMinCompletionsByWorkerThread() const {
  int minumum = completion_history_[0];
  for (int i = 0; i < thread_count_; ++i)
    minumum = std::min(minumum, completion_history_[i]);
  return minumum;
}

int WorkQueue::GetMaxCompletionsByWorkerThread() const {
  int maximum = completion_history_[0];
  for (int i = 0; i < thread_count_; ++i)
    maximum = std::max(maximum, completion_history_[i]);
  return maximum;
}

int WorkQueue::GetNumThreadsTakingAssignments() const {
  int count = 0;
  for (int i = 0; i < thread_count_; ++i)
    if (assignment_history_[i])
      count++;
  return count;
}

int WorkQueue::GetNumThreadsCompletingTasks() const {
  int count = 0;
  for (int i = 0; i < thread_count_; ++i)
    if (completion_history_[i])
      count++;
  return count;
}

int WorkQueue::GetNumberOfCompletedTasks() const {
  int total = 0;
  for (int i = 0; i < thread_count_; ++i)
    total += completion_history_[i];
  return total;
}

TimeDelta WorkQueue::GetWorkTime() const {
  return worker_delay_;
}

void WorkQueue::SetWorkTime(TimeDelta delay) {
  worker_delay_ = delay;
}

void WorkQueue::SetTaskCount(int count) {
  task_count_ = count;
}

void WorkQueue::SetAllowHelp(bool allow) {
  allow_help_requests_ = allow;
}

void WorkQueue::SetShutdown() {
  lock_.AssertAcquired();
  shutdown_ = true;
}

//------------------------------------------------------------------------------
// Define the standard worker task. Several tests will spin out many of these
// threads.
//------------------------------------------------------------------------------

// The multithread tests involve several threads with a task to perform as
// directed by an instance of the class WorkQueue.
// The task is to:
// a) Check to see if there are more tasks (there is a task counter).
//    a1) Wait on condition variable if there are no tasks currently.
// b) Call a function to see what should be done.
// c) Do some computation based on the number of milliseconds returned in (b).
// d) go back to (a).

// WorkQueue::ThreadMain() implements the above task for all threads.
// It calls the controlling object to tell the creator about progress, and to
// ask about tasks.

void WorkQueue::ThreadMain() {
  int thread_id;
  {
    AutoLock auto_lock(lock_);
    thread_id = GetThreadId();
    if (EveryIdWasAllocated())
      all_threads_have_ids()->Signal();  // Tell creator we're ready.
  }

  Lock private_lock;  // Used to waste time on "our work".
  while (1) {  // This is the main consumer loop.
    TimeDelta work_time;
    bool could_use_help;
    {
      AutoLock auto_lock(lock_);
      while (0 == task_count() && !shutdown()) {
        work_is_available()->Wait();
      }
      if (shutdown()) {
        // Ack the notification of a shutdown message back to the controller.
        thread_shutting_down();
        return;  // Terminate.
      }
      // Get our task duration from the queue.
      work_time = GetAnAssignment(thread_id);
      could_use_help = (task_count() > 0) && allow_help_requests();
    }  // Release lock

    // Do work (outside of locked region.
    if (could_use_help)
      work_is_available()->Signal();  // Get help from other threads.

    if (work_time > TimeDelta::FromMilliseconds(0)) {
      // We could just sleep(), but we'll instead further exercise the
      // condition variable class, and do a timed wait.
      AutoLock auto_lock(private_lock);
      ConditionVariable private_cv(&private_lock);
      private_cv.TimedWait(work_time);  // Unsynchronized waiting.
    }

    {
      AutoLock auto_lock(lock_);
      // Send notification that we completed our "work."
      WorkIsCompleted(thread_id);
    }
  }
}

}  // namespace