Move unittests that had a _test filename to _unittest. Update some missing tests in the SCons build.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@1375 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 658 insertions, 0 deletions

diff --git a/base/condition_variable_unittest.cc b/base/condition_variable_unittest.cc
new file mode 100644
index 0000000..3632f11a8
--- /dev/null
+++ b/base/condition_variable_unittest.cc
@@ -0,0 +1,658 @@
+// 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/logging.h"
+#include "base/platform_thread.h"
+#include "base/scoped_ptr.h"
+#include "base/spin_wait.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+//------------------------------------------------------------------------------
+// Define our test class, with several common variables.
+//------------------------------------------------------------------------------
+
+class ConditionVariableTest : public testing::Test {
+ 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.
+  int shutdown_task_count() const;
+
+  void thread_shutting_down();
+  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;
+
+  void SetWorkTime(TimeDelta delay);
+  void SetTaskCount(int count);
+  void SetAllowHelp(bool allow);
+
+  void SetShutdown();
+
+ 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.
+};
+
+//------------------------------------------------------------------------------
+// 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_F(ConditionVariableTest, MultiThreadConsumerTest) {
+  const int kThreadCount = 10;
+  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(kTenMs);
+
+  {
+    // 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 one worker do 3 30ms tasks.
+    queue.ResetHistory();
+    queue.SetTaskCount(3);
+    queue.SetWorkTime(kThirtyMs);
+    queue.SetAllowHelp(false);
+  }
+  queue.work_is_available()->Signal();  // Start up one thread.
+  // Wait to allow solo worker insufficient time to get done.
+  private_cv.TimedWait(kFortyFiveMs);  // Should take about 90 ms.
+
+  {
+    // Check that all work HASN'T completed yet.
+    AutoLock auto_lock(*queue.lock());
+    EXPECT_EQ(1, queue.GetNumThreadsTakingAssignments());
+    EXPECT_EQ(1, queue.GetNumThreadsCompletingTasks());
+    EXPECT_GT(2, queue.task_count());  // 2 should have started.
+    EXPECT_GT(3, queue.GetMaxCompletionsByWorkerThread());
+    EXPECT_EQ(0, queue.GetMinCompletionsByWorkerThread());
+    EXPECT_EQ(1, queue.GetNumberOfCompletedTasks());
+  }
+  // Wait to allow solo workers to get done.
+  private_cv.TimedWait(kSixtyMs);  // Should take about 45ms more.
+
+  {
+    // 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(3, queue.GetMaxCompletionsByWorkerThread());
+    EXPECT_EQ(0, queue.GetMinCompletionsByWorkerThread());
+    EXPECT_EQ(3, queue.GetNumberOfCompletedTasks());
+
+    // Set up to make each task include getting help from another worker.
+    queue.ResetHistory();
+    queue.SetTaskCount(3);
+    queue.SetWorkTime(kThirtyMs);
+    queue.SetAllowHelp(true);
+  }
+  queue.work_is_available()->Signal();  // But each worker can signal another.
+  // Wait to allow the 3 workers to get done.
+  private_cv.TimedWait(kFortyFiveMs);  // Should  take about 30 ms.
+
+  {
+    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());
+
+    // 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.
+  private_cv.TimedWait(kFortyFiveMs);
+
+  {
+    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.
+  private_cv.TimedWait(kOneHundredMs);
+
+  {
+    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.
+  private_cv.TimedWait(kOneHundredMs);  // 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.
+  private_cv.TimedWait(kOneHundredMs);  // 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.shutdown_task_count() == 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.shutdown_task_count() == 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() {
+  DCHECK(!EveryIdWasAllocated());
+  return thread_started_counter_++;  // Give out Unique IDs.
+}
+
+bool WorkQueue::EveryIdWasAllocated() const {
+  return thread_count_ == thread_started_counter_;
+}
+
+TimeDelta WorkQueue::GetAnAssignment(int thread_id) {
+  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) {
+  completion_history_[thread_id]++;
+}
+
+int WorkQueue::task_count() const {
+  return task_count_;
+}
+
+bool WorkQueue::allow_help_requests() const {
+  return allow_help_requests_;
+}
+
+bool WorkQueue::shutdown() const {
+  return shutdown_;
+}
+
+int WorkQueue::shutdown_task_count() const {
+  return shutdown_task_count_;
+}
+
+void WorkQueue::thread_shutting_down() {
+  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;
+}
+
+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() {
+  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
+