Revert of Revert "Allow SequencedTaskRunnerHandle::Get() while running unsequenced tasks."

base/threading/sequenced_worker_pool.cc

 // Copyright (c) 2012 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 "base/threading/sequenced_worker_pool.h"
 
 #include <stdint.h>
 
 #include <list>
 #include <map>
@@ skipping 308 matching lines @@
                 SequenceToken sequence_token,
                 WorkerShutdown shutdown_behavior,
                 const tracked_objects::Location& from_here,
                 const Closure& task,
                 TimeDelta delay);
 
   bool RunsTasksOnCurrentThread() const;
 
   bool IsRunningSequenceOnCurrentThread(SequenceToken sequence_token) const;
 
+  bool IsRunningSequence(SequenceToken sequence_token) const;
+
+  void SetRunningTaskInfoForCurrentThread(SequenceToken sequence_token,
+                                          WorkerShutdown shutdown_behavior);
+
   void CleanupForTesting();
 
   void SignalHasWorkForTesting();
 
   int GetWorkSignalCountForTesting() const;
 
   void Shutdown(int max_blocking_tasks_after_shutdown);
 
   bool IsShutdownInProgress();
 
@@ skipping 355 matching lines @@
 bool SequencedWorkerPool::Inner::IsRunningSequenceOnCurrentThread(
     SequenceToken sequence_token) const {
   AutoLock lock(lock_);
   ThreadMap::const_iterator found = threads_.find(PlatformThread::CurrentId());
   if (found == threads_.end())
     return false;
   return found->second->is_processing_task() &&
          sequence_token.Equals(found->second->task_sequence_token());
 }
 
+bool SequencedWorkerPool::Inner::IsRunningSequence(
+    SequenceToken sequence_token) const {
+  DCHECK(sequence_token.IsValid());
+  AutoLock lock(lock_);
+  return !IsSequenceTokenRunnable(sequence_token.id_);
+}
+
+void SequencedWorkerPool::Inner::SetRunningTaskInfoForCurrentThread(
+    SequenceToken sequence_token,
+    WorkerShutdown shutdown_behavior) {
+  AutoLock lock(lock_);
+  ThreadMap::const_iterator found = threads_.find(PlatformThread::CurrentId());
+  DCHECK(found != threads_.end());
+  DCHECK(found->second->is_processing_task());
+  DCHECK(!found->second->task_sequence_token().IsValid());
+  found->second->set_running_task_info(sequence_token, shutdown_behavior);
+
+  // Mark the sequence token as in use.
+  bool success = current_sequences_.insert(sequence_token.id_).second;
+  DCHECK(success);
+}
+
 // See https://code.google.com/p/chromium/issues/detail?id=168415
 void SequencedWorkerPool::Inner::CleanupForTesting() {
   DCHECK(!RunsTasksOnCurrentThread());
   base::ThreadRestrictions::ScopedAllowWait allow_wait;
   AutoLock lock(lock_);
   CHECK_EQ(CLEANUP_DONE, cleanup_state_);
   if (shutdown_called_)
     return;
   if (pending_tasks_.empty() && waiting_thread_count_ == threads_.size())
     return;
@@ skipping 105 matching lines @@
               SequenceToken(task.sequence_token_id), task.shutdown_behavior);
 
           tracked_objects::TaskStopwatch stopwatch;
           stopwatch.Start();
           task.task.Run();
           stopwatch.Stop();
 
           tracked_objects::ThreadData::TallyRunOnNamedThreadIfTracking(
               task, stopwatch);
 
+          // Update the sequence token in case it has been set from within the
+          // task, so it can be removed from the set of currently running
+          // sequences in DidRunWorkerTask() below.
+          task.sequence_token_id = this_worker->task_sequence_token().id_;
+
           // Make sure our task is erased outside the lock for the
           // same reason we do this with delete_these_oustide_lock.
           // Also, do it before calling reset_running_task_info() so
           // that sequence-checking from within the task's destructor
           // still works.
           task.task = Closure();
 
           this_worker->reset_running_task_info();
         }
         DidRunWorkerTask(task);  // Must be done inside the lock.
@@ skipping 363 matching lines @@
 // static
 scoped_refptr<SequencedWorkerPool>
 SequencedWorkerPool::GetWorkerPoolForCurrentThread() {
   Worker* worker = Worker::GetForCurrentThread();
   if (!worker)
     return nullptr;
 
   return worker->worker_pool();
 }
 
+// static
+scoped_refptr<SequencedTaskRunner>
+SequencedWorkerPool::GetSequencedTaskRunnerForCurrentThread() {
+  Worker* worker = Worker::GetForCurrentThread();
+
+  // If there is no worker, this thread is not a worker thread. Otherwise, it is
+  // currently running a task (sequenced or unsequenced).
+  if (!worker)
+    return nullptr;
+
+  scoped_refptr<SequencedWorkerPool> pool = worker->worker_pool();
+  SequenceToken sequence_token = worker->task_sequence_token();
+  WorkerShutdown shutdown_behavior = worker->task_shutdown_behavior();
+  if (!sequence_token.IsValid()) {
+    // Create a new sequence token and bind this thread to it, to make sure that
+    // a task posted to the SequencedTaskRunner we are going to return is not
+    // immediately going to run on a different thread.
+    sequence_token = Inner::GetSequenceToken();
+    pool->inner_->SetRunningTaskInfoForCurrentThread(sequence_token,
+                                                     shutdown_behavior);
+  }
+
+  DCHECK(pool->IsRunningSequenceOnCurrentThread(sequence_token));
+  return new SequencedWorkerPoolSequencedTaskRunner(
+      std::move(pool), sequence_token, shutdown_behavior);
+}
+
 SequencedWorkerPool::SequencedWorkerPool(size_t max_threads,
                                          const std::string& thread_name_prefix,
                                          base::TaskPriority task_priority)
     : constructor_task_runner_(ThreadTaskRunnerHandle::Get()),
       inner_(new Inner(this,
                        max_threads,
                        thread_name_prefix,
                        task_priority,
                        NULL)) {}
 
@@ skipping 124 matching lines @@
 
 bool SequencedWorkerPool::RunsTasksOnCurrentThread() const {
   return inner_->RunsTasksOnCurrentThread();
 }
 
 bool SequencedWorkerPool::IsRunningSequenceOnCurrentThread(
     SequenceToken sequence_token) const {
   return inner_->IsRunningSequenceOnCurrentThread(sequence_token);
 }
 
+bool SequencedWorkerPool::IsRunningSequence(
+    SequenceToken sequence_token) const {
+  return inner_->IsRunningSequence(sequence_token);
+}
+
 void SequencedWorkerPool::FlushForTesting() {
   inner_->CleanupForTesting();
 }
 
 void SequencedWorkerPool::SignalHasWorkForTesting() {
   inner_->SignalHasWorkForTesting();
 }
 
 void SequencedWorkerPool::Shutdown(int max_new_blocking_tasks_after_shutdown) {
   DCHECK(constructor_task_runner_->BelongsToCurrentThread());
   inner_->Shutdown(max_new_blocking_tasks_after_shutdown);
 }
 
 bool SequencedWorkerPool::IsShutdownInProgress() {
   return inner_->IsShutdownInProgress();
 }
 
 }  // namespace base