Make SchedulerSingleThreadTaskRunner::RunsTasksOnCurrentThread sequence-affine.

base/task_scheduler/scheduler_worker_pool_impl.cc

 // Copyright 2016 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/task_scheduler/scheduler_worker_pool_impl.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <utility>
@@ skipping 23 matching lines @@
 
 constexpr char kPoolNameSuffix[] = "Pool";
 constexpr char kDetachDurationHistogramPrefix[] =
     "TaskScheduler.DetachDuration.";
 constexpr char kNumTasksBeforeDetachHistogramPrefix[] =
     "TaskScheduler.NumTasksBeforeDetach.";
 constexpr char kNumTasksBetweenWaitsHistogramPrefix[] =
     "TaskScheduler.NumTasksBetweenWaits.";
 constexpr char kTaskLatencyHistogramPrefix[] = "TaskScheduler.TaskLatency.";
 
-// SchedulerWorker that owns the current thread, if any.
-LazyInstance<ThreadLocalPointer<const SchedulerWorker>>::Leaky
-    tls_current_worker = LAZY_INSTANCE_INITIALIZER;
-
 // SchedulerWorkerPool that owns the current thread, if any.
 LazyInstance<ThreadLocalPointer<const SchedulerWorkerPool>>::Leaky
     tls_current_worker_pool = LAZY_INSTANCE_INITIALIZER;
 
 // A task runner that runs tasks with the PARALLEL ExecutionMode.
 class SchedulerParallelTaskRunner : public TaskRunner {
  public:
   // Constructs a SchedulerParallelTaskRunner which can be used to post tasks so
   // long as |worker_pool| is alive.
   // TODO(robliao): Find a concrete way to manage |worker_pool|'s memory.
@@ skipping 136 matching lines @@
   }
 
   bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
                                   const Closure& closure,
                                   base::TimeDelta delay) override {
     // Tasks are never nested within the task scheduler.
     return PostDelayedTask(from_here, closure, delay);
   }
 
   bool RunsTasksOnCurrentThread() const override {
-    return tls_current_worker.Get().Get() == worker_;
+    // Even though this is a SingleThreadTaskRunner, test the actual sequence
+    // instead of the assigned worker so that another task randomly assigned
+    // to the same worker doesn't return true by happenstance.

[robliao, 2016/11/03 22:59:56]

Nit: s/happenstance/coincidence/ ?

+    return sequence_->token() == SequenceToken::GetForCurrentThread();
   }
 
  private:
   ~SchedulerSingleThreadTaskRunner() override;
 
   // Sequence for all Tasks posted through this TaskRunner.
   const scoped_refptr<Sequence> sequence_ = new Sequence;
 
   const TaskTraits traits_;
   SchedulerWorkerPool* const worker_pool_;
@@ skipping 283 matching lines @@
   DCHECK_EQ(num_tasks_since_last_wait_, 0U);
 
   if (!last_detach_time_.is_null()) {
     outer_->detach_duration_histogram_->AddTime(TimeTicks::Now() -
                                                 last_detach_time_);
   }
 
   PlatformThread::SetName(
       StringPrintf("TaskScheduler%sWorker%d", outer_->name_.c_str(), index_));
 
-  DCHECK(!tls_current_worker.Get().Get());
   DCHECK(!tls_current_worker_pool.Get().Get());
-  tls_current_worker.Get().Set(worker);
   tls_current_worker_pool.Get().Set(outer_);
 
   // New threads haven't run GetWork() yet, so reset the |idle_start_time_|.
   idle_start_time_ = TimeTicks();
 
   ThreadRestrictions::SetIOAllowed(
       outer_->io_restriction_ ==
           SchedulerWorkerPoolParams::IORestriction::ALLOWED);
 }
 
@@ skipping 272 matching lines @@
   AutoSchedulerLock auto_lock(idle_workers_stack_lock_);
   idle_workers_stack_.Remove(worker);
 }
 
 bool SchedulerWorkerPoolImpl::CanWorkerDetachForTesting() {
   return !worker_detachment_disallowed_.IsSet();
 }
 
 }  // namespace internal
 }  // namespace base