TaskScheduler: List posted Sequences on SchedulerParallelTaskRunner

Bug: 889029
Change-Id: I189f7a33aec070d882712f7360223cdc804b0fbf
Reviewed-on: https://chromium-review.googlesource.com/c/1312929
Commit-Queue: Jesse McKenna <jessemckenna@google.com>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605103}

base/task/task_scheduler/scheduler_parallel_task_runner.cc

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "base/task/task_scheduler/scheduler_parallel_task_runner.h"
+#include "base/task/task_scheduler/scheduler_task_runner_delegate.h"
 
 #include "base/task/task_scheduler/sequence.h"
 
@@ -24,14 +25,27 @@ bool SchedulerParallelTaskRunner::PostDelayedTask(const Location& from_here,
     return false;
 
   // Post the task as part of a one-off single-task Sequence.
+  scoped_refptr<Sequence> sequence = MakeRefCounted<Sequence>(traits_, this);
+
+  {
+    AutoSchedulerLock auto_lock(lock_);
+    sequences_.insert(sequence.get());
+  }
+
   return scheduler_task_runner_delegate_->PostTaskWithSequence(
-      Task(from_here, std::move(closure), delay),
-      MakeRefCounted<Sequence>(traits_));
+      Task(from_here, std::move(closure), delay), std::move(sequence));
 }
 
 bool SchedulerParallelTaskRunner::RunsTasksInCurrentSequence() const {
   return scheduler_task_runner_delegate_->IsRunningPoolWithTraits(traits_);
 }
 
+void SchedulerParallelTaskRunner::UnregisterSequence(Sequence* sequence) {
+  DCHECK(sequence);
+
+  AutoSchedulerLock auto_lock(lock_);
+  sequences_.erase(sequence);
+}
+
 }  // namespace internal
 }  // namespace base

base/task/task_scheduler/scheduler_parallel_task_runner.h

@@ -7,8 +7,9 @@
 
 #include "base/base_export.h"
 #include "base/callback_forward.h"
+#include "base/containers/flat_set.h"
 #include "base/location.h"
-#include "base/task/task_scheduler/scheduler_task_runner_delegate.h"
+#include "base/task/task_scheduler/scheduler_lock.h"
 #include "base/task/task_traits.h"
 #include "base/task_runner.h"
 #include "base/time/time.h"
@@ -16,6 +17,9 @@
 namespace base {
 namespace internal {
 
+class Sequence;
+class SchedulerTaskRunnerDelegate;
+
 // A task runner that runs tasks in parallel.
 class BASE_EXPORT SchedulerParallelTaskRunner : public TaskRunner {
  public:
@@ -31,12 +35,23 @@ class BASE_EXPORT SchedulerParallelTaskRunner : public TaskRunner {
 
   bool RunsTasksInCurrentSequence() const override;
 
+  // Removes |sequence| from |sequences_|.
+  void UnregisterSequence(Sequence* sequence);
+
  private:
   ~SchedulerParallelTaskRunner() override;
 
   const TaskTraits traits_;
   SchedulerTaskRunnerDelegate* const scheduler_task_runner_delegate_;
 
+  // Synchronizes access to |sequences_|.
+  SchedulerLock lock_;
+
+  // List of alive Sequences instantiated by this SchedulerParallelTaskRunner.
+  // Sequences are added when they are instantiated, and removed when they are
+  // destroyed.
+  base::flat_set<Sequence*> sequences_;
+
   DISALLOW_COPY_AND_ASSIGN(SchedulerParallelTaskRunner);
 };
 

base/task/task_scheduler/sequence.cc

@@ -13,7 +13,11 @@
 namespace base {
 namespace internal {
 
-Sequence::Sequence(const TaskTraits& traits) : traits_(traits) {}
+Sequence::Sequence(
+    const TaskTraits& traits,
+    scoped_refptr<SchedulerParallelTaskRunner> scheduler_parallel_task_runner)
+    : traits_(traits),
+      scheduler_parallel_task_runner_(scheduler_parallel_task_runner) {}
 
 bool Sequence::PushTask(Task task) {
   // Use CHECK instead of DCHECK to crash earlier. See http://crbug.com/711167
@@ -64,7 +68,11 @@ SequenceSortKey Sequence::GetSortKey() const {
   return SequenceSortKey(traits_.priority(), next_task_sequenced_time);
 }
 
-Sequence::~Sequence() = default;
+Sequence::~Sequence() {
+  if (scheduler_parallel_task_runner_) {
+    scheduler_parallel_task_runner_->UnregisterSequence(this);
+  }
+}
 
 }  // namespace internal
 }  // namespace base

base/task/task_scheduler/sequence.h

@@ -14,6 +14,7 @@
 #include "base/optional.h"
 #include "base/sequence_token.h"
 #include "base/task/task_scheduler/scheduler_lock.h"
+#include "base/task/task_scheduler/scheduler_parallel_task_runner.h"
 #include "base/task/task_scheduler/sequence_sort_key.h"
 #include "base/task/task_scheduler/task.h"
 #include "base/task/task_traits.h"
@@ -43,7 +44,11 @@ namespace internal {
 class BASE_EXPORT Sequence : public RefCountedThreadSafe<Sequence> {
  public:
   // |traits| is metadata that applies to all Tasks in the Sequence.
-  explicit Sequence(const TaskTraits& traits);
+  // |scheduler_parallel_task_runner| is a reference to the
+  // SchedulerParallelTaskRunner that created this Sequence, if any.
+  Sequence(const TaskTraits& traits,
+           scoped_refptr<SchedulerParallelTaskRunner>
+               scheduler_parallel_task_runner = nullptr);
 
   // Adds |task| in a new slot at the end of the Sequence. Returns true if the
   // Sequence was empty before this operation.
@@ -97,6 +102,12 @@ class BASE_EXPORT Sequence : public RefCountedThreadSafe<Sequence> {
   // The TaskTraits of all Tasks in the Sequence.
   const TaskTraits traits_;
 
+  // A reference to the SchedulerParallelTaskRunner that created this Sequence,
+  // if any. Used to remove Sequence from the TaskRunner's list of Sequence
+  // references when Sequence is deleted.
+  const scoped_refptr<SchedulerParallelTaskRunner>
+      scheduler_parallel_task_runner_;
+
   DISALLOW_COPY_AND_ASSIGN(Sequence);
 };
 

base/task/task_scheduler/task_tracker_posix_unittest.cc

@@ -56,7 +56,7 @@ TEST_F(TaskSchedulerTaskTrackerPosixTest, RunTask) {
   Task task(FROM_HERE,
             Bind([](bool* did_run) { *did_run = true; }, Unretained(&did_run)),
             TimeDelta());
-  TaskTraits default_traits = {};
+  constexpr TaskTraits default_traits = {};
 
   EXPECT_TRUE(tracker_.WillPostTask(&task, default_traits.shutdown_behavior()));
 
@@ -78,7 +78,7 @@ TEST_F(TaskSchedulerTaskTrackerPosixTest, FileDescriptorWatcher) {
             Bind(IgnoreResult(&FileDescriptorWatcher::WatchReadable), fds[0],
                  DoNothing()),
             TimeDelta());
-  TaskTraits default_traits = {};
+  constexpr TaskTraits default_traits = {};
   // FileDescriptorWatcher::WatchReadable needs a SequencedTaskRunnerHandle.
   task.sequenced_task_runner_ref = MakeRefCounted<NullTaskRunner>();