Re-land: cc: Remove WorkerPool class and instead use TaskGraphRunner directly.

cc/resources/worker_pool.cc

Index: cc/resources/worker_pool.cc
diff --git a/cc/resources/worker_pool.cc b/cc/resources/worker_pool.cc
deleted file mode 100644
index aa1a948ec0a2638e5d37a13e184eb4e80b549def..0000000000000000000000000000000000000000
--- a/cc/resources/worker_pool.cc
+++ /dev/null
@@ -1,601 +0,0 @@
-// Copyright 2013 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.
-
-#include "cc/resources/worker_pool.h"
-
-#include <algorithm>
-
-#include "base/bind.h"
-#include "base/containers/hash_tables.h"
-#include "base/debug/trace_event.h"
-#include "base/lazy_instance.h"
-#include "base/memory/linked_ptr.h"
-#include "base/strings/stringprintf.h"
-#include "base/synchronization/condition_variable.h"
-#include "base/threading/simple_thread.h"
-#include "base/threading/thread_restrictions.h"
-#include "cc/base/scoped_ptr_deque.h"
-
-namespace cc {
-
-namespace {
-
-// TaskGraphRunners can process task graphs from multiple
-// workerpool instances. All members are guarded by |lock_|.
-class TaskGraphRunner : public base::DelegateSimpleThread::Delegate {
- public:
-  typedef WorkerPool::TaskGraph TaskGraph;
-  typedef WorkerPool::TaskVector TaskVector;
-
-  TaskGraphRunner(size_t num_threads, const std::string& thread_name_prefix);
-  virtual ~TaskGraphRunner();
-
-  void Register(const WorkerPool* worker_pool);
-  void Unregister(const WorkerPool* worker_pool);
-  // Schedule running of tasks in |graph|. Tasks previously scheduled but
-  // no longer needed will be canceled unless already running. Canceled
-  // tasks are moved to |completed_tasks| without being run. The result
-  // is that once scheduled, a task is guaranteed to end up in the
-  // |completed_tasks| queue even if it later get canceled by another
-  // call to SetTaskGraph().
-  void SetTaskGraph(const WorkerPool* worker_pool, TaskGraph* graph);
-
-  // Wait for all scheduled tasks to finish running.
-  void WaitForTasksToFinishRunning(const WorkerPool* worker_pool);
-
-  // Collect all completed tasks in |completed_tasks|.
-  void CollectCompletedTasks(const WorkerPool* worker_pool,
-                             TaskVector* completed_tasks);
-
- private:
-  static bool CompareTaskPriority(const internal::GraphNode* a,
-                                  const internal::GraphNode* b) {
-    // In this system, numerically lower priority is run first.
-    if (a->priority() != b->priority())
-      return a->priority() > b->priority();
-
-    // Run task with most dependents first when priority is the same.
-    return a->dependents().size() < b->dependents().size();
-  }
-
-  struct TaskNamespace {
-    // This set contains all pending tasks.
-    TaskGraph pending_tasks;
-    // This set contains all currently running tasks.
-    TaskGraph running_tasks;
-    // Completed tasks not yet collected by origin thread.
-    TaskVector completed_tasks;
-    // Ordered set of tasks that are ready to run.
-    internal::GraphNode::Vector ready_to_run_tasks;
-  };
-
-  static bool CompareTaskNamespacePriority(const TaskNamespace* a,
-                                           const TaskNamespace* b) {
-    DCHECK(!a->ready_to_run_tasks.empty());
-    DCHECK(!b->ready_to_run_tasks.empty());
-
-    // Compare based on task priority of the ready_to_run_tasks heap
-    // .front() will hold the max element of the heap,
-    // except after pop_heap, when max element is moved to .back().
-    return CompareTaskPriority(a->ready_to_run_tasks.front(),
-                               b->ready_to_run_tasks.front());
-  }
-
-  typedef std::map<const WorkerPool*, linked_ptr<TaskNamespace> >
-      TaskNamespaceMap;
-
-  // Overridden from base::DelegateSimpleThread:
-  virtual void Run() OVERRIDE;
-
-  inline bool has_finished_running_tasks(TaskNamespace* task_namespace) {
-    return (task_namespace->pending_tasks.empty() &&
-            task_namespace->running_tasks.empty());
-  }
-
-  // This lock protects all members of this class except
-  // |worker_pool_on_origin_thread_|. Do not read or modify anything
-  // without holding this lock. Do not block while holding this lock.
-  mutable base::Lock lock_;
-
-  // Condition variable that is waited on by worker threads until new
-  // tasks are ready to run or shutdown starts.
-  base::ConditionVariable has_ready_to_run_tasks_cv_;
-
-  // Condition variable that is waited on by origin threads until a
-  // namespace has finished running all associated tasks.
-  base::ConditionVariable has_namespaces_with_finished_running_tasks_cv_;
-
-  // Provides each running thread loop with a unique index. First thread
-  // loop index is 0.
-  unsigned next_thread_index_;
-
-  // Set during shutdown. Tells workers to exit when no more tasks
-  // are pending.
-  bool shutdown_;
-
-  // This set contains all registered namespaces.
-  TaskNamespaceMap namespaces_;
-
-  // Ordered set of task namespaces that have ready to run tasks.
-  std::vector<TaskNamespace*> ready_to_run_namespaces_;
-
-  ScopedPtrDeque<base::DelegateSimpleThread> workers_;
-
-  DISALLOW_COPY_AND_ASSIGN(TaskGraphRunner);
-};
-
-TaskGraphRunner::TaskGraphRunner(
-    size_t num_threads, const std::string& thread_name_prefix)
-    : lock_(),
-      has_ready_to_run_tasks_cv_(&lock_),
-      has_namespaces_with_finished_running_tasks_cv_(&lock_),
-      next_thread_index_(0),
-      shutdown_(false) {
-  base::AutoLock lock(lock_);
-
-  while (workers_.size() < num_threads) {
-    scoped_ptr<base::DelegateSimpleThread> worker = make_scoped_ptr(
-        new base::DelegateSimpleThread(
-            this,
-            thread_name_prefix +
-            base::StringPrintf(
-                "Worker%u",
-                static_cast<unsigned>(workers_.size() + 1)).c_str()));
-    worker->Start();
-#if defined(OS_ANDROID) || defined(OS_LINUX)
-    worker->SetThreadPriority(base::kThreadPriority_Background);
-#endif
-    workers_.push_back(worker.Pass());
-  }
-}
-
-TaskGraphRunner::~TaskGraphRunner() {
-  {
-    base::AutoLock lock(lock_);
-
-    DCHECK_EQ(0u, ready_to_run_namespaces_.size());
-    DCHECK_EQ(0u, namespaces_.size());
-
-    DCHECK(!shutdown_);
-    shutdown_ = true;
-
-    // Wake up a worker so it knows it should exit. This will cause all workers
-    // to exit as each will wake up another worker before exiting.
-    has_ready_to_run_tasks_cv_.Signal();
-  }
-
-  while (workers_.size()) {
-    scoped_ptr<base::DelegateSimpleThread> worker = workers_.take_front();
-    // http://crbug.com/240453 - Join() is considered IO and will block this
-    // thread. See also http://crbug.com/239423 for further ideas.
-    base::ThreadRestrictions::ScopedAllowIO allow_io;
-    worker->Join();
-  }
-}
-
-void TaskGraphRunner::Register(const WorkerPool* worker_pool) {
-  base::AutoLock lock(lock_);
-
-  DCHECK(namespaces_.find(worker_pool) == namespaces_.end());
-  linked_ptr<TaskNamespace> task_set = make_linked_ptr(new TaskNamespace());
-  namespaces_[worker_pool] = task_set;
-}
-
-void TaskGraphRunner::Unregister(const WorkerPool* worker_pool) {
-  base::AutoLock lock(lock_);
-
-  DCHECK(namespaces_.find(worker_pool) != namespaces_.end());
-  DCHECK_EQ(0u, namespaces_[worker_pool]->pending_tasks.size());
-  DCHECK_EQ(0u, namespaces_[worker_pool]->ready_to_run_tasks.size());
-  DCHECK_EQ(0u, namespaces_[worker_pool]->running_tasks.size());
-  DCHECK_EQ(0u, namespaces_[worker_pool]->completed_tasks.size());
-
-  namespaces_.erase(worker_pool);
-}
-
-void TaskGraphRunner::WaitForTasksToFinishRunning(
-    const WorkerPool* worker_pool) {
-  base::AutoLock lock(lock_);
-
-  DCHECK(namespaces_.find(worker_pool) != namespaces_.end());
-  TaskNamespace* task_namespace = namespaces_[worker_pool].get();
-
-  while (!has_finished_running_tasks(task_namespace))
-    has_namespaces_with_finished_running_tasks_cv_.Wait();
-
-  // There may be other namespaces that have finished running
-  // tasks, so wake up another origin thread.
-  has_namespaces_with_finished_running_tasks_cv_.Signal();
-}
-
-void TaskGraphRunner::SetTaskGraph(const WorkerPool* worker_pool,
-                                   TaskGraph* graph) {
-  TaskGraph new_pending_tasks;
-  TaskGraph new_running_tasks;
-
-  new_pending_tasks.swap(*graph);
-
-  {
-    base::AutoLock lock(lock_);
-
-    DCHECK(!shutdown_);
-    DCHECK(namespaces_.find(worker_pool) != namespaces_.end());
-    TaskNamespace* task_namespace = namespaces_[worker_pool].get();
-
-    // First remove all completed tasks from |new_pending_tasks| and
-    // adjust number of dependencies.
-    for (TaskVector::iterator it = task_namespace->completed_tasks.begin();
-         it != task_namespace->completed_tasks.end(); ++it) {
-      internal::WorkerPoolTask* task = it->get();
-
-      scoped_ptr<internal::GraphNode> node = new_pending_tasks.take_and_erase(
-          task);
-      if (node) {
-        for (internal::GraphNode::Vector::const_iterator it =
-                 node->dependents().begin();
-             it != node->dependents().end(); ++it) {
-          internal::GraphNode* dependent_node = *it;
-          dependent_node->remove_dependency();
-        }
-      }
-    }
-
-    // Build new running task set.
-    for (TaskGraph::iterator it = task_namespace->running_tasks.begin();
-         it != task_namespace->running_tasks.end(); ++it) {
-      internal::WorkerPoolTask* task = it->first;
-      // Transfer scheduled task value from |new_pending_tasks| to
-      // |new_running_tasks| if currently running. Value must be set to
-      // NULL if |new_pending_tasks| doesn't contain task. This does
-      // the right in both cases.
-      new_running_tasks.set(task, new_pending_tasks.take_and_erase(task));
-    }
-
-    // Build new "ready to run" tasks queue.
-    task_namespace->ready_to_run_tasks.clear();
-    for (TaskGraph::iterator it = new_pending_tasks.begin();
-         it != new_pending_tasks.end(); ++it) {
-      internal::WorkerPoolTask* task = it->first;
-      DCHECK(task);
-      internal::GraphNode* node = it->second;
-
-      // Completed tasks should not exist in |new_pending_tasks|.
-      DCHECK(!task->HasFinishedRunning());
-
-      // Call DidSchedule() to indicate that this task has been scheduled.
-      // Note: This is only for debugging purposes.
-      task->DidSchedule();
-
-      if (!node->num_dependencies())
-        task_namespace->ready_to_run_tasks.push_back(node);
-
-      // Erase the task from old pending tasks.
-      task_namespace->pending_tasks.erase(task);
-    }
-
-    // Rearrange the elements in |ready_to_run_tasks| in such a way that
-    // they form a heap.
-    std::make_heap(task_namespace->ready_to_run_tasks.begin(),
-                   task_namespace->ready_to_run_tasks.end(),
-                   CompareTaskPriority);
-
-    task_namespace->completed_tasks.reserve(
-        task_namespace->completed_tasks.size() +
-        task_namespace->pending_tasks.size());
-
-    // The items left in |pending_tasks| need to be canceled.
-    for (TaskGraph::const_iterator it = task_namespace->pending_tasks.begin();
-         it != task_namespace->pending_tasks.end(); ++it) {
-      task_namespace->completed_tasks.push_back(it->first);
-    }
-
-    // Swap task sets.
-    // Note: old tasks are intentionally destroyed after releasing |lock_|.
-    task_namespace->pending_tasks.swap(new_pending_tasks);
-    task_namespace->running_tasks.swap(new_running_tasks);
-
-    // If |ready_to_run_tasks| is empty, it means we either have
-    // running tasks, or we have no pending tasks.
-    DCHECK(!task_namespace->ready_to_run_tasks.empty() ||
-           (task_namespace->pending_tasks.empty() ||
-            !task_namespace->running_tasks.empty()));
-
-    // Build new "ready to run" task namespaces queue.
-    ready_to_run_namespaces_.clear();
-    for (TaskNamespaceMap::iterator it = namespaces_.begin();
-         it != namespaces_.end(); ++it) {
-      if (!it->second->ready_to_run_tasks.empty())
-        ready_to_run_namespaces_.push_back(it->second.get());
-    }
-
-    // Rearrange the task namespaces in |ready_to_run_namespaces_|
-    // in such a way that they form a heap.
-    std::make_heap(ready_to_run_namespaces_.begin(),
-                   ready_to_run_namespaces_.end(),
-                   CompareTaskNamespacePriority);
-
-    // If there is more work available, wake up worker thread.
-    if (!ready_to_run_namespaces_.empty())
-      has_ready_to_run_tasks_cv_.Signal();
-  }
-}
-
-void TaskGraphRunner::CollectCompletedTasks(
-    const WorkerPool* worker_pool, TaskVector* completed_tasks) {
-  base::AutoLock lock(lock_);
-
-  DCHECK_EQ(0u, completed_tasks->size());
-  DCHECK(namespaces_.find(worker_pool) != namespaces_.end());
-  completed_tasks->swap(namespaces_[worker_pool]->completed_tasks);
-}
-
-void TaskGraphRunner::Run() {
-  base::AutoLock lock(lock_);
-
-  // Get a unique thread index.
-  int thread_index = next_thread_index_++;
-
-  while (true) {
-    if (ready_to_run_namespaces_.empty()) {
-      // Exit when shutdown is set and no more tasks are pending.
-      if (shutdown_)
-        break;
-
-      // Wait for more tasks.
-      has_ready_to_run_tasks_cv_.Wait();
-      continue;
-    }
-
-    // Take top priority TaskNamespace from |ready_to_run_namespaces_|.
-    std::pop_heap(ready_to_run_namespaces_.begin(),
-                  ready_to_run_namespaces_.end(),
-                  CompareTaskNamespacePriority);
-    TaskNamespace* task_namespace = ready_to_run_namespaces_.back();
-    ready_to_run_namespaces_.pop_back();
-    DCHECK(!task_namespace->ready_to_run_tasks.empty());
-
-    // Take top priority task from |ready_to_run_tasks|.
-    std::pop_heap(task_namespace->ready_to_run_tasks.begin(),
-                  task_namespace->ready_to_run_tasks.end(),
-                  CompareTaskPriority);
-    scoped_refptr<internal::WorkerPoolTask> task(
-        task_namespace->ready_to_run_tasks.back()->task());
-    task_namespace->ready_to_run_tasks.pop_back();
-
-    // Add task namespace back to |ready_to_run_namespaces_| if not
-    // empty after taking top priority task.
-    if (!task_namespace->ready_to_run_tasks.empty()) {
-      ready_to_run_namespaces_.push_back(task_namespace);
-      std::push_heap(ready_to_run_namespaces_.begin(),
-                     ready_to_run_namespaces_.end(),
-                     CompareTaskNamespacePriority);
-    }
-
-    // Move task from |pending_tasks| to |running_tasks|.
-    DCHECK(task_namespace->pending_tasks.contains(task.get()));
-    DCHECK(!task_namespace->running_tasks.contains(task.get()));
-    task_namespace->running_tasks.set(
-        task.get(),
-        task_namespace->pending_tasks.take_and_erase(task.get()));
-
-    // There may be more work available, so wake up another worker thread.
-    has_ready_to_run_tasks_cv_.Signal();
-
-    // Call WillRun() before releasing |lock_| and running task.
-    task->WillRun();
-
-    {
-      base::AutoUnlock unlock(lock_);
-
-      task->RunOnWorkerThread(thread_index);
-    }
-
-    // This will mark task as finished running.
-    task->DidRun();
-
-    // Now iterate over all dependents to remove dependency and check
-    // if they are ready to run.
-    scoped_ptr<internal::GraphNode> node =
-        task_namespace->running_tasks.take_and_erase(task.get());
-    if (node) {
-      bool ready_to_run_namespaces_has_heap_properties = true;
-
-      for (internal::GraphNode::Vector::const_iterator it =
-               node->dependents().begin();
-           it != node->dependents().end(); ++it) {
-        internal::GraphNode* dependent_node = *it;
-
-        dependent_node->remove_dependency();
-        // Task is ready if it has no dependencies. Add it to
-        // |ready_to_run_tasks_|.
-        if (!dependent_node->num_dependencies()) {
-          bool was_empty = task_namespace->ready_to_run_tasks.empty();
-          task_namespace->ready_to_run_tasks.push_back(dependent_node);
-          std::push_heap(task_namespace->ready_to_run_tasks.begin(),
-                         task_namespace->ready_to_run_tasks.end(),
-                         CompareTaskPriority);
-          // Task namespace is ready if it has at least one ready
-          // to run task. Add it to |ready_to_run_namespaces_| if
-          // it just become ready.
-          if (was_empty) {
-            DCHECK(std::find(ready_to_run_namespaces_.begin(),
-                             ready_to_run_namespaces_.end(),
-                             task_namespace) ==
-                   ready_to_run_namespaces_.end());
-            ready_to_run_namespaces_.push_back(task_namespace);
-          }
-          ready_to_run_namespaces_has_heap_properties = false;
-        }
-      }
-
-      // Rearrange the task namespaces in |ready_to_run_namespaces_|
-      // in such a way that they yet again form a heap.
-      if (!ready_to_run_namespaces_has_heap_properties) {
-        std::make_heap(ready_to_run_namespaces_.begin(),
-                       ready_to_run_namespaces_.end(),
-                       CompareTaskNamespacePriority);
-      }
-    }
-
-    // Finally add task to |completed_tasks_|.
-    task_namespace->completed_tasks.push_back(task);
-
-    // If namespace has finished running all tasks, wake up origin thread.
-    if (has_finished_running_tasks(task_namespace))
-      has_namespaces_with_finished_running_tasks_cv_.Signal();
-  }
-
-  // We noticed we should exit. Wake up the next worker so it knows it should
-  // exit as well (because the Shutdown() code only signals once).
-  has_ready_to_run_tasks_cv_.Signal();
-}
-
-class CompositorRasterTaskGraphRunner
-    : public TaskGraphRunner {
- public:
-  CompositorRasterTaskGraphRunner() : TaskGraphRunner(
-      WorkerPool::GetNumRasterThreads(), "CompositorRaster") {
-  }
-};
-
-base::LazyInstance<CompositorRasterTaskGraphRunner>
-    g_task_graph_runner = LAZY_INSTANCE_INITIALIZER;
-
-const int kDefaultNumRasterThreads = 1;
-
-int g_num_raster_threads = 0;
-
-}  // namespace
-
-namespace internal {
-
-WorkerPoolTask::WorkerPoolTask()
-    : did_schedule_(false),
-      did_run_(false),
-      did_complete_(false) {
-}
-
-WorkerPoolTask::~WorkerPoolTask() {
-  DCHECK_EQ(did_schedule_, did_complete_);
-  DCHECK(!did_run_ || did_schedule_);
-  DCHECK(!did_run_ || did_complete_);
-}
-
-void WorkerPoolTask::DidSchedule() {
-  DCHECK(!did_complete_);
-  did_schedule_ = true;
-}
-
-void WorkerPoolTask::WillRun() {
-  DCHECK(did_schedule_);
-  DCHECK(!did_complete_);
-  DCHECK(!did_run_);
-}
-
-void WorkerPoolTask::DidRun() {
-  did_run_ = true;
-}
-
-void WorkerPoolTask::WillComplete() {
-  DCHECK(!did_complete_);
-}
-
-void WorkerPoolTask::DidComplete() {
-  DCHECK(did_schedule_);
-  DCHECK(!did_complete_);
-  did_complete_ = true;
-}
-
-bool WorkerPoolTask::HasFinishedRunning() const {
-  return did_run_;
-}
-
-bool WorkerPoolTask::HasCompleted() const {
-  return did_complete_;
-}
-
-GraphNode::GraphNode(internal::WorkerPoolTask* task, unsigned priority)
-    : task_(task),
-      priority_(priority),
-      num_dependencies_(0) {
-}
-
-GraphNode::~GraphNode() {
-}
-
-}  // namespace internal
-
-// static
-void WorkerPool::SetNumRasterThreads(int num_threads) {
-  DCHECK_LT(0, num_threads);
-  DCHECK_EQ(0, g_num_raster_threads);
-
-  g_num_raster_threads = num_threads;
-}
-
-// static
-int WorkerPool::GetNumRasterThreads() {
-  if (!g_num_raster_threads)
-    g_num_raster_threads = kDefaultNumRasterThreads;
-
-  return g_num_raster_threads;
-}
-
-WorkerPool::WorkerPool() : in_dispatch_completion_callbacks_(false) {
-  g_task_graph_runner.Pointer()->Register(this);
-}
-
-WorkerPool::~WorkerPool() {
-  g_task_graph_runner.Pointer()->Unregister(this);
-}
-
-void WorkerPool::Shutdown() {
-  TRACE_EVENT0("cc", "WorkerPool::Shutdown");
-
-  DCHECK(!in_dispatch_completion_callbacks_);
-
-  g_task_graph_runner.Pointer()->WaitForTasksToFinishRunning(this);
-}
-
-void WorkerPool::SetTaskGraph(TaskGraph* graph) {
-  TRACE_EVENT1("cc", "WorkerPool::SetTaskGraph",
-               "num_tasks", graph->size());
-
-  DCHECK(!in_dispatch_completion_callbacks_);
-
-  g_task_graph_runner.Pointer()->SetTaskGraph(this, graph);
-}
-
-void WorkerPool::CheckForCompletedWorkerTasks() {
-  TRACE_EVENT0("cc", "WorkerPool::CheckForCompletedWorkerTasks");
-
-  DCHECK(!in_dispatch_completion_callbacks_);
-
-  TaskVector completed_tasks;
-  g_task_graph_runner.Pointer()->CollectCompletedTasks(this, &completed_tasks);
-  ProcessCompletedTasks(completed_tasks);
-}
-
-void WorkerPool::ProcessCompletedTasks(
-    const TaskVector& completed_tasks) {
-  TRACE_EVENT1("cc", "WorkerPool::ProcessCompletedTasks",
-               "completed_task_count", completed_tasks.size());
-
-  // Worker pool instance is not reentrant while processing completed tasks.
-  in_dispatch_completion_callbacks_ = true;
-
-  for (TaskVector::const_iterator it = completed_tasks.begin();
-       it != completed_tasks.end();
-       ++it) {
-    internal::WorkerPoolTask* task = it->get();
-
-    task->WillComplete();
-    task->CompleteOnOriginThread();
-    task->DidComplete();
-  }
-
-  in_dispatch_completion_callbacks_ = false;
-}
-
-}  // namespace cc