base/synchronization/condition_variable_unittest.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // Multi-threaded tests of ConditionVariable class.
   6
   7 #include <time.h>
   8 #include <algorithm>
   9 #include <vector>
  10
  11 #include "base/bind.h"
  12 #include "base/logging.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "base/synchronization/condition_variable.h"
  15 #include "base/synchronization/lock.h"
  16 #include "base/synchronization/spin_wait.h"
  17 #include "base/threading/platform_thread.h"
  18 #include "base/threading/thread.h"
  19 #include "base/threading/thread_collision_warner.h"
  20 #include "base/time/time.h"
  21 #include "testing/gtest/include/gtest/gtest.h"
  22 #include "testing/platform_test.h"
  23
  24 namespace base {
  25
  26 namespace {
  27 //------------------------------------------------------------------------------
  28 // Define our test class, with several common variables.
  29 //------------------------------------------------------------------------------
  30
  31 class ConditionVariableTest : public PlatformTest {
  32  public:
  33   const TimeDelta kZeroMs;
  34   const TimeDelta kTenMs;
  35   const TimeDelta kThirtyMs;
  36   const TimeDelta kFortyFiveMs;
  37   const TimeDelta kSixtyMs;
  38   const TimeDelta kOneHundredMs;
  39
  40   ConditionVariableTest()
  41       : kZeroMs(TimeDelta::FromMilliseconds(0)),
  42         kTenMs(TimeDelta::FromMilliseconds(10)),
  43         kThirtyMs(TimeDelta::FromMilliseconds(30)),
  44         kFortyFiveMs(TimeDelta::FromMilliseconds(45)),
  45         kSixtyMs(TimeDelta::FromMilliseconds(60)),
  46         kOneHundredMs(TimeDelta::FromMilliseconds(100)) {
  47   }
  48 };
  49
  50 //------------------------------------------------------------------------------
  51 // Define a class that will control activities an several multi-threaded tests.
  52 // The general structure of multi-threaded tests is that a test case will
  53 // construct an instance of a WorkQueue.  The WorkQueue will spin up some
  54 // threads and control them throughout their lifetime, as well as maintaining
  55 // a central repository of the work thread's activity.  Finally, the WorkQueue
  56 // will command the the worker threads to terminate.  At that point, the test
  57 // cases will validate that the WorkQueue has records showing that the desired
  58 // activities were performed.
  59 //------------------------------------------------------------------------------
  60
  61 // Callers are responsible for synchronizing access to the following class.
  62 // The WorkQueue::lock_, as accessed via WorkQueue::lock(), should be used for
  63 // all synchronized access.
  64 class WorkQueue : public PlatformThread::Delegate {
  65  public:
  66   explicit WorkQueue(int thread_count);
  67   ~WorkQueue() override;
  68
  69   // PlatformThread::Delegate interface.
  70   void ThreadMain() override;
  71
  72   //----------------------------------------------------------------------------
  73   // Worker threads only call the following methods.
  74   // They should use the lock to get exclusive access.
  75   int GetThreadId();  // Get an ID assigned to a thread..
  76   bool EveryIdWasAllocated() const;  // Indicates that all IDs were handed out.
  77   TimeDelta GetAnAssignment(int thread_id);  // Get a work task duration.
  78   void WorkIsCompleted(int thread_id);
  79
  80   int task_count() const;
  81   bool allow_help_requests() const;  // Workers can signal more workers.
  82   bool shutdown() const;  // Check if shutdown has been requested.
  83
  84   void thread_shutting_down();
  85
  86
  87   //----------------------------------------------------------------------------
  88   // Worker threads can call them but not needed to acquire a lock.
  89   Lock* lock();
  90
  91   ConditionVariable* work_is_available();
  92   ConditionVariable* all_threads_have_ids();
  93   ConditionVariable* no_more_tasks();
  94
  95   //----------------------------------------------------------------------------
  96   // The rest of the methods are for use by the controlling master thread (the
  97   // test case code).
  98   void ResetHistory();
  99   int GetMinCompletionsByWorkerThread() const;
 100   int GetMaxCompletionsByWorkerThread() const;
 101   int GetNumThreadsTakingAssignments() const;
 102   int GetNumThreadsCompletingTasks() const;
 103   int GetNumberOfCompletedTasks() const;
 104
 105   void SetWorkTime(TimeDelta delay);
 106   void SetTaskCount(int count);
 107   void SetAllowHelp(bool allow);
 108
 109   // The following must be called without locking, and will spin wait until the
 110   // threads are all in a wait state.
 111   void SpinUntilAllThreadsAreWaiting();
 112   void SpinUntilTaskCountLessThan(int task_count);
 113
 114   // Caller must acquire lock before calling.
 115   void SetShutdown();
 116
 117   // Compares the |shutdown_task_count_| to the |thread_count| and returns true
 118   // if they are equal.  This check will acquire the |lock_| so the caller
 119   // should not hold the lock when calling this method.
 120   bool ThreadSafeCheckShutdown(int thread_count);
 121
 122  private:
 123   // Both worker threads and controller use the following to synchronize.
 124   Lock lock_;
 125   ConditionVariable work_is_available_;  // To tell threads there is work.
 126
 127   // Conditions to notify the controlling process (if it is interested).
 128   ConditionVariable all_threads_have_ids_;  // All threads are running.
 129   ConditionVariable no_more_tasks_;  // Task count is zero.
 130
 131   const int thread_count_;
 132   int waiting_thread_count_;
 133   scoped_ptr<PlatformThreadHandle[]> thread_handles_;
 134   std::vector<int> assignment_history_;  // Number of assignment per worker.
 135   std::vector<int> completion_history_;  // Number of completions per worker.
 136   int thread_started_counter_;  // Used to issue unique id to workers.
 137   int shutdown_task_count_;  // Number of tasks told to shutdown
 138   int task_count_;  // Number of assignment tasks waiting to be processed.
 139   TimeDelta worker_delay_;  // Time each task takes to complete.
 140   bool allow_help_requests_;  // Workers can signal more workers.
 141   bool shutdown_;  // Set when threads need to terminate.
 142
 143   DFAKE_MUTEX(locked_methods_);
 144 };
 145
 146 //------------------------------------------------------------------------------
 147 // The next section contains the actual tests.
 148 //------------------------------------------------------------------------------
 149
 150 TEST_F(ConditionVariableTest, StartupShutdownTest) {
 151   Lock lock;
 152
 153   // First try trivial startup/shutdown.
 154   {
 155     ConditionVariable cv1(&lock);
 156   }  // Call for cv1 destruction.
 157
 158   // Exercise with at least a few waits.
 159   ConditionVariable cv(&lock);
 160
 161   lock.Acquire();
 162   cv.TimedWait(kTenMs);  // Wait for 10 ms.
 163   cv.TimedWait(kTenMs);  // Wait for 10 ms.
 164   lock.Release();
 165
 166   lock.Acquire();
 167   cv.TimedWait(kTenMs);  // Wait for 10 ms.
 168   cv.TimedWait(kTenMs);  // Wait for 10 ms.
 169   cv.TimedWait(kTenMs);  // Wait for 10 ms.
 170   lock.Release();
 171 }  // Call for cv destruction.
 172
 173 TEST_F(ConditionVariableTest, TimeoutTest) {
 174   Lock lock;
 175   ConditionVariable cv(&lock);
 176   lock.Acquire();
 177
 178   TimeTicks start = TimeTicks::Now();
 179   const TimeDelta WAIT_TIME = TimeDelta::FromMilliseconds(300);
 180   // Allow for clocking rate granularity.
 181   const TimeDelta FUDGE_TIME = TimeDelta::FromMilliseconds(50);
 182
 183   cv.TimedWait(WAIT_TIME + FUDGE_TIME);
 184   TimeDelta duration = TimeTicks::Now() - start;
 185   // We can't use EXPECT_GE here as the TimeDelta class does not support the
 186   // required stream conversion.
 187   EXPECT_TRUE(duration >= WAIT_TIME);
 188
 189   lock.Release();
 190 }
 191
 192 #if defined(OS_POSIX)
 193 const int kDiscontinuitySeconds = 2;
 194
 195 void BackInTime(Lock* lock) {
 196   AutoLock auto_lock(*lock);
 197
 198   timeval tv;
 199   gettimeofday(&tv, NULL);
 200   tv.tv_sec -= kDiscontinuitySeconds;
 201   settimeofday(&tv, NULL);
 202 }
 203
 204 // Tests that TimedWait ignores changes to the system clock.
 205 // Test is disabled by default, because it needs to run as root to muck with the
 206 // system clock.
 207 // http://crbug.com/293736
 208 TEST_F(ConditionVariableTest, DISABLED_TimeoutAcrossSetTimeOfDay) {
 209   timeval tv;
 210   gettimeofday(&tv, NULL);
 211   tv.tv_sec += kDiscontinuitySeconds;
 212   if (settimeofday(&tv, NULL) < 0) {
 213     PLOG(ERROR) << "Could not set time of day. Run as root?";
 214     return;
 215   }
 216
 217   Lock lock;
 218   ConditionVariable cv(&lock);
 219   lock.Acquire();
 220
 221   Thread thread("Helper");
 222   thread.Start();
 223   thread.message_loop()->PostTask(FROM_HERE, base::Bind(&BackInTime, &lock));
 224
 225   TimeTicks start = TimeTicks::Now();
 226   const TimeDelta kWaitTime = TimeDelta::FromMilliseconds(300);
 227   // Allow for clocking rate granularity.
 228   const TimeDelta kFudgeTime = TimeDelta::FromMilliseconds(50);
 229
 230   cv.TimedWait(kWaitTime + kFudgeTime);
 231   TimeDelta duration = TimeTicks::Now() - start;
 232
 233   thread.Stop();
 234   // We can't use EXPECT_GE here as the TimeDelta class does not support the
 235   // required stream conversion.
 236   EXPECT_TRUE(duration >= kWaitTime);
 237   EXPECT_TRUE(duration <= TimeDelta::FromSeconds(kDiscontinuitySeconds));
 238
 239   lock.Release();
 240 }
 241 #endif
 242
 243
 244 // Suddenly got flaky on Win, see http://crbug.com/10607 (starting at
 245 // comment #15).
 246 #if defined(OS_WIN)
 247 #define MAYBE_MultiThreadConsumerTest DISABLED_MultiThreadConsumerTest
 248 #else
 249 #define MAYBE_MultiThreadConsumerTest MultiThreadConsumerTest
 250 #endif
 251 // Test serial task servicing, as well as two parallel task servicing methods.
 252 TEST_F(ConditionVariableTest, MAYBE_MultiThreadConsumerTest) {
 253   const int kThreadCount = 10;
 254   WorkQueue queue(kThreadCount);  // Start the threads.
 255
 256   const int kTaskCount = 10;  // Number of tasks in each mini-test here.
 257
 258   Time start_time;  // Used to time task processing.
 259
 260   {
 261     base::AutoLock auto_lock(*queue.lock());
 262     while (!queue.EveryIdWasAllocated())
 263       queue.all_threads_have_ids()->Wait();
 264   }
 265
 266   // If threads aren't in a wait state, they may start to gobble up tasks in
 267   // parallel, short-circuiting (breaking) this test.
 268   queue.SpinUntilAllThreadsAreWaiting();
 269
 270   {
 271     // Since we have no tasks yet, all threads should be waiting by now.
 272     base::AutoLock auto_lock(*queue.lock());
 273     EXPECT_EQ(0, queue.GetNumThreadsTakingAssignments());
 274     EXPECT_EQ(0, queue.GetNumThreadsCompletingTasks());
 275     EXPECT_EQ(0, queue.task_count());
 276     EXPECT_EQ(0, queue.GetMaxCompletionsByWorkerThread());
 277     EXPECT_EQ(0, queue.GetMinCompletionsByWorkerThread());
 278     EXPECT_EQ(0, queue.GetNumberOfCompletedTasks());
 279
 280     // Set up to make each task include getting help from another worker, so
 281     // so that the work gets done in paralell.
 282     queue.ResetHistory();
 283     queue.SetTaskCount(kTaskCount);
 284     queue.SetWorkTime(kThirtyMs);
 285     queue.SetAllowHelp(true);
 286
 287     start_time = Time::Now();
 288   }
 289
 290   queue.work_is_available()->Signal();  // But each worker can signal another.
 291   // Wait till we at least start to handle tasks (and we're not all waiting).
 292   queue.SpinUntilTaskCountLessThan(kTaskCount);
 293   // Wait to allow the all workers to get done.
 294   queue.SpinUntilAllThreadsAreWaiting();
 295
 296   {
 297     // Wait until all work tasks have at least been assigned.
 298     base::AutoLock auto_lock(*queue.lock());
 299     while (queue.task_count())
 300       queue.no_more_tasks()->Wait();
 301
 302     // To avoid racy assumptions, we'll just assert that at least 2 threads
 303     // did work.  We know that the first worker should have gone to sleep, and
 304     // hence a second worker should have gotten an assignment.
 305     EXPECT_LE(2, queue.GetNumThreadsTakingAssignments());
 306     EXPECT_EQ(kTaskCount, queue.GetNumberOfCompletedTasks());
 307
 308     // Try to ask all workers to help, and only a few will do the work.
 309     queue.ResetHistory();
 310     queue.SetTaskCount(3);
 311     queue.SetWorkTime(kThirtyMs);
 312     queue.SetAllowHelp(false);
 313   }
 314   queue.work_is_available()->Broadcast();  // Make them all try.
 315   // Wait till we at least start to handle tasks (and we're not all waiting).
 316   queue.SpinUntilTaskCountLessThan(3);
 317   // Wait to allow the 3 workers to get done.
 318   queue.SpinUntilAllThreadsAreWaiting();
 319
 320   {
 321     base::AutoLock auto_lock(*queue.lock());
 322     EXPECT_EQ(3, queue.GetNumThreadsTakingAssignments());
 323     EXPECT_EQ(3, queue.GetNumThreadsCompletingTasks());
 324     EXPECT_EQ(0, queue.task_count());
 325     EXPECT_EQ(1, queue.GetMaxCompletionsByWorkerThread());
 326     EXPECT_EQ(0, queue.GetMinCompletionsByWorkerThread());
 327     EXPECT_EQ(3, queue.GetNumberOfCompletedTasks());
 328
 329     // Set up to make each task get help from another worker.
 330     queue.ResetHistory();
 331     queue.SetTaskCount(3);
 332     queue.SetWorkTime(kThirtyMs);
 333     queue.SetAllowHelp(true);  // Allow (unnecessary) help requests.
 334   }
 335   queue.work_is_available()->Broadcast();  // Signal all threads.
 336   // Wait till we at least start to handle tasks (and we're not all waiting).
 337   queue.SpinUntilTaskCountLessThan(3);
 338   // Wait to allow the 3 workers to get done.
 339   queue.SpinUntilAllThreadsAreWaiting();
 340
 341   {
 342     base::AutoLock auto_lock(*queue.lock());
 343     EXPECT_EQ(3, queue.GetNumThreadsTakingAssignments());
 344     EXPECT_EQ(3, queue.GetNumThreadsCompletingTasks());
 345     EXPECT_EQ(0, queue.task_count());
 346     EXPECT_EQ(1, queue.GetMaxCompletionsByWorkerThread());
 347     EXPECT_EQ(0, queue.GetMinCompletionsByWorkerThread());
 348     EXPECT_EQ(3, queue.GetNumberOfCompletedTasks());
 349
 350     // Set up to make each task get help from another worker.
 351     queue.ResetHistory();
 352     queue.SetTaskCount(20);  // 2 tasks per thread.
 353     queue.SetWorkTime(kThirtyMs);
 354     queue.SetAllowHelp(true);
 355   }
 356   queue.work_is_available()->Signal();  // But each worker can signal another.
 357   // Wait till we at least start to handle tasks (and we're not all waiting).
 358   queue.SpinUntilTaskCountLessThan(20);
 359   // Wait to allow the 10 workers to get done.
 360   queue.SpinUntilAllThreadsAreWaiting();  // Should take about 60 ms.
 361
 362   {
 363     base::AutoLock auto_lock(*queue.lock());
 364     EXPECT_EQ(10, queue.GetNumThreadsTakingAssignments());
 365     EXPECT_EQ(10, queue.GetNumThreadsCompletingTasks());
 366     EXPECT_EQ(0, queue.task_count());
 367     EXPECT_EQ(20, queue.GetNumberOfCompletedTasks());
 368
 369     // Same as last test, but with Broadcast().
 370     queue.ResetHistory();
 371     queue.SetTaskCount(20);  // 2 tasks per thread.
 372     queue.SetWorkTime(kThirtyMs);
 373     queue.SetAllowHelp(true);
 374   }
 375   queue.work_is_available()->Broadcast();
 376   // Wait till we at least start to handle tasks (and we're not all waiting).
 377   queue.SpinUntilTaskCountLessThan(20);
 378   // Wait to allow the 10 workers to get done.
 379   queue.SpinUntilAllThreadsAreWaiting();  // Should take about 60 ms.
 380
 381   {
 382     base::AutoLock auto_lock(*queue.lock());
 383     EXPECT_EQ(10, queue.GetNumThreadsTakingAssignments());
 384     EXPECT_EQ(10, queue.GetNumThreadsCompletingTasks());
 385     EXPECT_EQ(0, queue.task_count());
 386     EXPECT_EQ(20, queue.GetNumberOfCompletedTasks());
 387
 388     queue.SetShutdown();
 389   }
 390   queue.work_is_available()->Broadcast();  // Force check for shutdown.
 391
 392   SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(TimeDelta::FromMinutes(1),
 393                                    queue.ThreadSafeCheckShutdown(kThreadCount));
 394 }
 395
 396 TEST_F(ConditionVariableTest, LargeFastTaskTest) {
 397   const int kThreadCount = 200;
 398   WorkQueue queue(kThreadCount);  // Start the threads.
 399
 400   Lock private_lock;  // Used locally for master to wait.
 401   base::AutoLock private_held_lock(private_lock);
 402   ConditionVariable private_cv(&private_lock);
 403
 404   {
 405     base::AutoLock auto_lock(*queue.lock());
 406     while (!queue.EveryIdWasAllocated())
 407       queue.all_threads_have_ids()->Wait();
 408   }
 409
 410   // Wait a bit more to allow threads to reach their wait state.
 411   queue.SpinUntilAllThreadsAreWaiting();
 412
 413   {
 414     // Since we have no tasks, all threads should be waiting by now.
 415     base::AutoLock auto_lock(*queue.lock());
 416     EXPECT_EQ(0, queue.GetNumThreadsTakingAssignments());
 417     EXPECT_EQ(0, queue.GetNumThreadsCompletingTasks());
 418     EXPECT_EQ(0, queue.task_count());
 419     EXPECT_EQ(0, queue.GetMaxCompletionsByWorkerThread());
 420     EXPECT_EQ(0, queue.GetMinCompletionsByWorkerThread());
 421     EXPECT_EQ(0, queue.GetNumberOfCompletedTasks());
 422
 423     // Set up to make all workers do (an average of) 20 tasks.
 424     queue.ResetHistory();
 425     queue.SetTaskCount(20 * kThreadCount);
 426     queue.SetWorkTime(kFortyFiveMs);
 427     queue.SetAllowHelp(false);
 428   }
 429   queue.work_is_available()->Broadcast();  // Start up all threads.
 430   // Wait until we've handed out all tasks.
 431   {
 432     base::AutoLock auto_lock(*queue.lock());
 433     while (queue.task_count() != 0)
 434       queue.no_more_tasks()->Wait();
 435   }
 436
 437   // Wait till the last of the tasks complete.
 438   queue.SpinUntilAllThreadsAreWaiting();
 439
 440   {
 441     // With Broadcast(), every thread should have participated.
 442     // but with racing.. they may not all have done equal numbers of tasks.
 443     base::AutoLock auto_lock(*queue.lock());
 444     EXPECT_EQ(kThreadCount, queue.GetNumThreadsTakingAssignments());
 445     EXPECT_EQ(kThreadCount, queue.GetNumThreadsCompletingTasks());
 446     EXPECT_EQ(0, queue.task_count());
 447     EXPECT_LE(20, queue.GetMaxCompletionsByWorkerThread());
 448     EXPECT_EQ(20 * kThreadCount, queue.GetNumberOfCompletedTasks());
 449
 450     // Set up to make all workers do (an average of) 4 tasks.
 451     queue.ResetHistory();
 452     queue.SetTaskCount(kThreadCount * 4);
 453     queue.SetWorkTime(kFortyFiveMs);
 454     queue.SetAllowHelp(true);  // Might outperform Broadcast().
 455   }
 456   queue.work_is_available()->Signal();  // Start up one thread.
 457
 458   // Wait until we've handed out all tasks
 459   {
 460     base::AutoLock auto_lock(*queue.lock());
 461     while (queue.task_count() != 0)
 462       queue.no_more_tasks()->Wait();
 463   }
 464
 465   // Wait till the last of the tasks complete.
 466   queue.SpinUntilAllThreadsAreWaiting();
 467
 468   {
 469     // With Signal(), every thread should have participated.
 470     // but with racing.. they may not all have done four tasks.
 471     base::AutoLock auto_lock(*queue.lock());
 472     EXPECT_EQ(kThreadCount, queue.GetNumThreadsTakingAssignments());
 473     EXPECT_EQ(kThreadCount, queue.GetNumThreadsCompletingTasks());
 474     EXPECT_EQ(0, queue.task_count());
 475     EXPECT_LE(4, queue.GetMaxCompletionsByWorkerThread());
 476     EXPECT_EQ(4 * kThreadCount, queue.GetNumberOfCompletedTasks());
 477
 478     queue.SetShutdown();
 479   }
 480   queue.work_is_available()->Broadcast();  // Force check for shutdown.
 481
 482   // Wait for shutdowns to complete.
 483   SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(TimeDelta::FromMinutes(1),
 484                                    queue.ThreadSafeCheckShutdown(kThreadCount));
 485 }
 486
 487 //------------------------------------------------------------------------------
 488 // Finally we provide the implementation for the methods in the WorkQueue class.
 489 //------------------------------------------------------------------------------
 490
 491 WorkQueue::WorkQueue(int thread_count)
 492   : lock_(),
 493     work_is_available_(&lock_),
 494     all_threads_have_ids_(&lock_),
 495     no_more_tasks_(&lock_),
 496     thread_count_(thread_count),
 497     waiting_thread_count_(0),
 498     thread_handles_(new PlatformThreadHandle[thread_count]),
 499     assignment_history_(thread_count),
 500     completion_history_(thread_count),
 501     thread_started_counter_(0),
 502     shutdown_task_count_(0),
 503     task_count_(0),
 504     allow_help_requests_(false),
 505     shutdown_(false) {
 506   EXPECT_GE(thread_count_, 1);
 507   ResetHistory();
 508   SetTaskCount(0);
 509   SetWorkTime(TimeDelta::FromMilliseconds(30));
 510
 511   for (int i = 0; i < thread_count_; ++i) {
 512     PlatformThreadHandle pth;
 513     EXPECT_TRUE(PlatformThread::Create(0, this, &pth));
 514     thread_handles_[i] = pth;
 515   }
 516 }
 517
 518 WorkQueue::~WorkQueue() {
 519   {
 520     base::AutoLock auto_lock(lock_);
 521     SetShutdown();
 522   }
 523   work_is_available_.Broadcast();  // Tell them all to terminate.
 524
 525   for (int i = 0; i < thread_count_; ++i) {
 526     PlatformThread::Join(thread_handles_[i]);
 527   }
 528   EXPECT_EQ(0, waiting_thread_count_);
 529 }
 530
 531 int WorkQueue::GetThreadId() {
 532   DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
 533   DCHECK(!EveryIdWasAllocated());
 534   return thread_started_counter_++;  // Give out Unique IDs.
 535 }
 536
 537 bool WorkQueue::EveryIdWasAllocated() const {
 538   DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
 539   return thread_count_ == thread_started_counter_;
 540 }
 541
 542 TimeDelta WorkQueue::GetAnAssignment(int thread_id) {
 543   DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
 544   DCHECK_LT(0, task_count_);
 545   assignment_history_[thread_id]++;
 546   if (0 == --task_count_) {
 547     no_more_tasks_.Signal();
 548   }
 549   return worker_delay_;
 550 }
 551
 552 void WorkQueue::WorkIsCompleted(int thread_id) {
 553   DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
 554   completion_history_[thread_id]++;
 555 }
 556
 557 int WorkQueue::task_count() const {
 558   DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
 559   return task_count_;
 560 }
 561
 562 bool WorkQueue::allow_help_requests() const {
 563   DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
 564   return allow_help_requests_;
 565 }
 566
 567 bool WorkQueue::shutdown() const {
 568   lock_.AssertAcquired();
 569   DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
 570   return shutdown_;
 571 }
 572
 573 // Because this method is called from the test's main thread we need to actually
 574 // take the lock.  Threads will call the thread_shutting_down() method with the
 575 // lock already acquired.
 576 bool WorkQueue::ThreadSafeCheckShutdown(int thread_count) {
 577   bool all_shutdown;
 578   base::AutoLock auto_lock(lock_);
 579   {
 580     // Declare in scope so DFAKE is guranteed to be destroyed before AutoLock.
 581     DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
 582     all_shutdown = (shutdown_task_count_ == thread_count);
 583   }
 584   return all_shutdown;
 585 }
 586
 587 void WorkQueue::thread_shutting_down() {
 588   lock_.AssertAcquired();
 589   DFAKE_SCOPED_RECURSIVE_LOCK(locked_methods_);
 590   shutdown_task_count_++;
 591 }
 592
 593 Lock* WorkQueue::lock() {
 594   return &lock_;
 595 }
 596
 597 ConditionVariable* WorkQueue::work_is_available() {
 598   return &work_is_available_;
 599 }
 600
 601 ConditionVariable* WorkQueue::all_threads_have_ids() {
 602   return &all_threads_have_ids_;
 603 }
 604
 605 ConditionVariable* WorkQueue::no_more_tasks() {
 606   return &no_more_tasks_;
 607 }
 608
 609 void WorkQueue::ResetHistory() {
 610   for (int i = 0; i < thread_count_; ++i) {
 611     assignment_history_[i] = 0;
 612     completion_history_[i] = 0;
 613   }
 614 }
 615
 616 int WorkQueue::GetMinCompletionsByWorkerThread() const {
 617   int minumum = completion_history_[0];
 618   for (int i = 0; i < thread_count_; ++i)
 619     minumum = std::min(minumum, completion_history_[i]);
 620   return minumum;
 621 }
 622
 623 int WorkQueue::GetMaxCompletionsByWorkerThread() const {
 624   int maximum = completion_history_[0];
 625   for (int i = 0; i < thread_count_; ++i)
 626     maximum = std::max(maximum, completion_history_[i]);
 627   return maximum;
 628 }
 629
 630 int WorkQueue::GetNumThreadsTakingAssignments() const {
 631   int count = 0;
 632   for (int i = 0; i < thread_count_; ++i)
 633     if (assignment_history_[i])
 634       count++;
 635   return count;
 636 }
 637
 638 int WorkQueue::GetNumThreadsCompletingTasks() const {
 639   int count = 0;
 640   for (int i = 0; i < thread_count_; ++i)
 641     if (completion_history_[i])
 642       count++;
 643   return count;
 644 }
 645
 646 int WorkQueue::GetNumberOfCompletedTasks() const {
 647   int total = 0;
 648   for (int i = 0; i < thread_count_; ++i)
 649     total += completion_history_[i];
 650   return total;
 651 }
 652
 653 void WorkQueue::SetWorkTime(TimeDelta delay) {
 654   worker_delay_ = delay;
 655 }
 656
 657 void WorkQueue::SetTaskCount(int count) {
 658   task_count_ = count;
 659 }
 660
 661 void WorkQueue::SetAllowHelp(bool allow) {
 662   allow_help_requests_ = allow;
 663 }
 664
 665 void WorkQueue::SetShutdown() {
 666   lock_.AssertAcquired();
 667   shutdown_ = true;
 668 }
 669
 670 void WorkQueue::SpinUntilAllThreadsAreWaiting() {
 671   while (true) {
 672     {
 673       base::AutoLock auto_lock(lock_);
 674       if (waiting_thread_count_ == thread_count_)
 675         break;
 676     }
 677     PlatformThread::Sleep(TimeDelta::FromMilliseconds(30));
 678   }
 679 }
 680
 681 void WorkQueue::SpinUntilTaskCountLessThan(int task_count) {
 682   while (true) {
 683     {
 684       base::AutoLock auto_lock(lock_);
 685       if (task_count_ < task_count)
 686         break;
 687     }
 688     PlatformThread::Sleep(TimeDelta::FromMilliseconds(30));
 689   }
 690 }
 691
 692
 693 //------------------------------------------------------------------------------
 694 // Define the standard worker task. Several tests will spin out many of these
 695 // threads.
 696 //------------------------------------------------------------------------------
 697
 698 // The multithread tests involve several threads with a task to perform as
 699 // directed by an instance of the class WorkQueue.
 700 // The task is to:
 701 // a) Check to see if there are more tasks (there is a task counter).
 702 //    a1) Wait on condition variable if there are no tasks currently.
 703 // b) Call a function to see what should be done.
 704 // c) Do some computation based on the number of milliseconds returned in (b).
 705 // d) go back to (a).
 706
 707 // WorkQueue::ThreadMain() implements the above task for all threads.
 708 // It calls the controlling object to tell the creator about progress, and to
 709 // ask about tasks.
 710
 711 void WorkQueue::ThreadMain() {
 712   int thread_id;
 713   {
 714     base::AutoLock auto_lock(lock_);
 715     thread_id = GetThreadId();
 716     if (EveryIdWasAllocated())
 717       all_threads_have_ids()->Signal();  // Tell creator we're ready.
 718   }
 719
 720   Lock private_lock;  // Used to waste time on "our work".
 721   while (1) {  // This is the main consumer loop.
 722     TimeDelta work_time;
 723     bool could_use_help;
 724     {
 725       base::AutoLock auto_lock(lock_);
 726       while (0 == task_count() && !shutdown()) {
 727         ++waiting_thread_count_;
 728         work_is_available()->Wait();
 729         --waiting_thread_count_;
 730       }
 731       if (shutdown()) {
 732         // Ack the notification of a shutdown message back to the controller.
 733         thread_shutting_down();
 734         return;  // Terminate.
 735       }
 736       // Get our task duration from the queue.
 737       work_time = GetAnAssignment(thread_id);
 738       could_use_help = (task_count() > 0) && allow_help_requests();
 739     }  // Release lock
 740
 741     // Do work (outside of locked region.
 742     if (could_use_help)
 743       work_is_available()->Signal();  // Get help from other threads.
 744
 745     if (work_time > TimeDelta::FromMilliseconds(0)) {
 746       // We could just sleep(), but we'll instead further exercise the
 747       // condition variable class, and do a timed wait.
 748       base::AutoLock auto_lock(private_lock);
 749       ConditionVariable private_cv(&private_lock);
 750       private_cv.TimedWait(work_time);  // Unsynchronized waiting.
 751     }
 752
 753     {
 754       base::AutoLock auto_lock(lock_);
 755       // Send notification that we completed our "work."
 756       WorkIsCompleted(thread_id);
 757     }
 758   }
 759 }
 760
 761 }  // namespace
 762
 763 }  // namespace base