SchedulerWorker Refcounting for Destruction in Production

base/task_scheduler/scheduler_worker_unittest.cc

Index: base/task_scheduler/scheduler_worker_unittest.cc
diff --git a/base/task_scheduler/scheduler_worker_unittest.cc b/base/task_scheduler/scheduler_worker_unittest.cc
index b65d50c07c3fb5db64ba8df08031bc6934ef10a5..b8dea8e7454e5a41c432e49180e893e0e074d788 100644
--- a/base/task_scheduler/scheduler_worker_unittest.cc
+++ b/base/task_scheduler/scheduler_worker_unittest.cc
@@ -13,13 +13,16 @@
 #include "base/bind_helpers.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
+#include "base/memory/ref_counted.h"
 #include "base/synchronization/condition_variable.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/task_scheduler/scheduler_lock.h"
 #include "base/task_scheduler/sequence.h"
 #include "base/task_scheduler/task.h"
 #include "base/task_scheduler/task_tracker.h"
+#include "base/test/test_timeouts.h"
 #include "base/threading/platform_thread.h"
+#include "base/threading/simple_thread.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "testing/gmock/include/gmock/gmock.h"
@@ -121,7 +124,7 @@ class TaskSchedulerWorkerTest : public testing::TestWithParam<size_t> {
     return re_enqueued_sequences_;
   }
 
-  std::unique_ptr<SchedulerWorker> worker_;
+  scoped_refptr<SchedulerWorker> worker_;
 
  private:
   class TestSchedulerWorkerDelegate : public SchedulerWorkerDefaultDelegate {
@@ -355,34 +358,92 @@ namespace {
 
 class ControllableDetachDelegate : public SchedulerWorkerDefaultDelegate {
  public:
-  ControllableDetachDelegate(TaskTracker* task_tracker)
-      : task_tracker_(task_tracker),
-        work_processed_(WaitableEvent::ResetPolicy::MANUAL,
-                        WaitableEvent::InitialState::NOT_SIGNALED),
-        detach_requested_(WaitableEvent::ResetPolicy::MANUAL,
+  class Controls : public RefCountedThreadSafe<Controls> {
+   public:
+    Controls()
+        : work_running_(WaitableEvent::ResetPolicy::MANUAL,
+                        WaitableEvent::InitialState::SIGNALED),
+          work_processed_(WaitableEvent::ResetPolicy::MANUAL,
                           WaitableEvent::InitialState::NOT_SIGNALED),
-        detached_(WaitableEvent::ResetPolicy::MANUAL,
-                  WaitableEvent::InitialState::NOT_SIGNALED) {
-    EXPECT_TRUE(task_tracker_);
-  }
+          detach_requested_(WaitableEvent::ResetPolicy::MANUAL,
+                            WaitableEvent::InitialState::NOT_SIGNALED),
+          detached_(WaitableEvent::ResetPolicy::MANUAL,
+                    WaitableEvent::InitialState::NOT_SIGNALED),
+          can_detach_block_(WaitableEvent::ResetPolicy::MANUAL,
+                            WaitableEvent::InitialState::SIGNALED),
+          destroyed_(WaitableEvent::ResetPolicy::MANUAL,
+                     WaitableEvent::InitialState::NOT_SIGNALED) {}
 
-  ~ControllableDetachDelegate() override = default;
+    void HaveWorkBlock() { work_running_.Reset(); }
 
-  // SchedulerWorker::Delegate:
-  MOCK_METHOD1(OnMainEntry, void(SchedulerWorker* worker));
+    void UnblockWork() { work_running_.Signal(); }
+
+    void MakeCanDetachBlock() { can_detach_block_.Reset(); }
+
+    void UnblockCanDetach() { can_detach_block_.Signal(); }
+
+    void WaitForWorkToRun() { work_processed_.Wait(); }
+
+    void WaitForDetachRequest() { detach_requested_.Wait(); }
+
+    void WaitForDetach() { detached_.Wait(); }
+
+    void WaitForDelegateDestroy() { destroyed_.Wait(); }
+
+    void ResetState() {
+      work_running_.Signal();
+      work_processed_.Reset();
+      detach_requested_.Reset();
+      can_detach_block_.Signal();
+      work_requested_ = false;
+    }
+
+    void set_can_detach(bool can_detach) { can_detach_ = can_detach; }
+
+   private:
+    friend class ControllableDetachDelegate;
+    friend class RefCountedThreadSafe<Controls>;
+    ~Controls() = default;
+
+    WaitableEvent work_running_;
+    WaitableEvent work_processed_;
+    WaitableEvent detach_requested_;
+    WaitableEvent detached_;
+    WaitableEvent can_detach_block_;
+    WaitableEvent destroyed_;
+
+    bool can_detach_ = false;
+    bool work_requested_ = false;
+
+    DISALLOW_COPY_AND_ASSIGN(Controls);
+  };
+
+  ControllableDetachDelegate(TaskTracker* task_tracker)
+      : task_tracker_(task_tracker), controls_(new Controls()) {}
+
+  ~ControllableDetachDelegate() override { controls_->destroyed_.Signal(); }
 
   scoped_refptr<Sequence> GetWork(SchedulerWorker* worker)
       override {
     // Sends one item of work to signal |work_processed_|. On subsequent calls,
     // sends nullptr to indicate there's no more work to be done.
-    if (work_requested_)
+    if (controls_->work_requested_)
       return nullptr;
 
-    work_requested_ = true;
+    controls_->work_requested_ = true;
     scoped_refptr<Sequence> sequence(new Sequence);
     std::unique_ptr<Task> task(new Task(
-        FROM_HERE, Bind(&WaitableEvent::Signal, Unretained(&work_processed_)),
-        TaskTraits(), TimeDelta()));
+        FROM_HERE,
+        Bind(
+            [](WaitableEvent* work_processed, WaitableEvent* work_running) {
+              work_processed->Signal();
+              work_running->Wait();
+            },
+            Unretained(&controls_->work_processed_),
+            Unretained(&controls_->work_running_)),
+        TaskTraits().WithBaseSyncPrimitives().WithShutdownBehavior(
+            TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN),
+        TimeDelta()));
     EXPECT_TRUE(task_tracker_->WillPostTask(task.get()));
     sequence->PushTask(std::move(task));
     return sequence;
@@ -391,43 +452,42 @@ class ControllableDetachDelegate : public SchedulerWorkerDefaultDelegate {
   void DidRunTask() override {}
 
   bool CanDetach(SchedulerWorker* worker) override {
-    detach_requested_.Signal();
-    return can_detach_;
+    // Saving |can_detach_| now so that callers waiting on |detach_requested_|
+    // have the thread go to sleep and then allow detachment.
+    bool can_detach = controls_->can_detach_;
+    controls_->detach_requested_.Signal();
+    controls_->can_detach_block_.Wait();
+    return can_detach;
   }
 
   void OnDetach() override {
-    EXPECT_TRUE(can_detach_);
-    EXPECT_TRUE(detach_requested_.IsSignaled());
-    detached_.Signal();
+    EXPECT_TRUE(controls_->can_detach_);
+    EXPECT_TRUE(controls_->detach_requested_.IsSignaled());
+    controls_->detached_.Signal();
   }
 
-  void WaitForWorkToRun() {
-    work_processed_.Wait();
-  }
+  // ControllableDetachDelegate:
+  scoped_refptr<Controls> controls() { return controls_; }
 
-  void WaitForDetachRequest() {
-    detach_requested_.Wait();
-  }
+ private:
+  scoped_refptr<Sequence> work_sequence_;
+  TaskTracker* const task_tracker_;
+  scoped_refptr<Controls> controls_;
 
-  void WaitForDetach() { detached_.Wait(); }
+  DISALLOW_COPY_AND_ASSIGN(ControllableDetachDelegate);
+};
 
-  void ResetState() {
-    work_requested_ = false;
-    work_processed_.Reset();
-    detach_requested_.Reset();
-  }
+class MockedControllableDetachDelegate : public ControllableDetachDelegate {
+ public:
+  MockedControllableDetachDelegate(TaskTracker* task_tracker)
+      : ControllableDetachDelegate(task_tracker){};
+  ~MockedControllableDetachDelegate() = default;
 
-  void set_can_detach(bool can_detach) { can_detach_ = can_detach; }
+  // SchedulerWorker::Delegate:
+  MOCK_METHOD1(OnMainEntry, void(SchedulerWorker* worker));
 
  private:
-  TaskTracker* const task_tracker_;
-  bool work_requested_ = false;
-  bool can_detach_ = false;
-  WaitableEvent work_processed_;
-  WaitableEvent detach_requested_;
-  WaitableEvent detached_;
-
-  DISALLOW_COPY_AND_ASSIGN(ControllableDetachDelegate);
+  DISALLOW_COPY_AND_ASSIGN(MockedControllableDetachDelegate);
 };
 
 }  // namespace
@@ -435,50 +495,232 @@ class ControllableDetachDelegate : public SchedulerWorkerDefaultDelegate {
 TEST(TaskSchedulerWorkerTest, WorkerDetaches) {
   TaskTracker task_tracker;
   // Will be owned by SchedulerWorker.
-  ControllableDetachDelegate* delegate =
-      new StrictMock<ControllableDetachDelegate>(&task_tracker);
-  delegate->set_can_detach(true);
+  MockedControllableDetachDelegate* delegate =
+      new StrictMock<MockedControllableDetachDelegate>(&task_tracker);
+  scoped_refptr<ControllableDetachDelegate::Controls> controls =
+      delegate->controls();
+  controls->set_can_detach(true);
   EXPECT_CALL(*delegate, OnMainEntry(_));
-  std::unique_ptr<SchedulerWorker> worker =
-      SchedulerWorker::Create(
-          ThreadPriority::NORMAL, WrapUnique(delegate), &task_tracker,
-          SchedulerWorker::InitialState::ALIVE);
+  scoped_refptr<SchedulerWorker> worker = SchedulerWorker::Create(
+      ThreadPriority::NORMAL, WrapUnique(delegate), &task_tracker,
+      SchedulerWorker::InitialState::ALIVE);
   worker->WakeUp();
-  delegate->WaitForWorkToRun();
+  controls->WaitForWorkToRun();
   Mock::VerifyAndClear(delegate);
-  delegate->WaitForDetachRequest();
-  delegate->WaitForDetach();
+  controls->WaitForDetachRequest();
+  controls->WaitForDetach();
   ASSERT_FALSE(worker->ThreadAliveForTesting());
 }
 
+TEST(TaskSchedulerWorkerTest, WorkerCleanupBeforeDetach) {
+  TaskTracker task_tracker;
+  // Will be owned by SchedulerWorker.
+  // No mock here as that's reasonably covered by other tests and the delegate
+  // may destroy on a different thread. Mocks aren't designed with that in mind.
+  std::unique_ptr<ControllableDetachDelegate> delegate =
+      MakeUnique<ControllableDetachDelegate>(&task_tracker);
+  scoped_refptr<ControllableDetachDelegate::Controls> controls =
+      delegate->controls();
+
+  controls->set_can_detach(true);
+  controls->MakeCanDetachBlock();
+
+  scoped_refptr<SchedulerWorker> worker = SchedulerWorker::Create(
+      ThreadPriority::NORMAL, std::move(delegate), &task_tracker,
+      SchedulerWorker::InitialState::ALIVE);
+  worker->WakeUp();
+
+  controls->WaitForDetachRequest();
+  worker->Cleanup();
+  worker = nullptr;
+  controls->UnblockCanDetach();
+  controls->WaitForDelegateDestroy();
+}
+
+TEST(TaskSchedulerWorkerTest, WorkerCleanupAfterDetach) {
+  TaskTracker task_tracker;
+  // Will be owned by SchedulerWorker.
+  // No mock here as that's reasonably covered by other tests and the delegate
+  // may destroy on a different thread. Mocks aren't designed with that in mind.
+  std::unique_ptr<ControllableDetachDelegate> delegate =
+      MakeUnique<ControllableDetachDelegate>(&task_tracker);
+  scoped_refptr<ControllableDetachDelegate::Controls> controls =
+      delegate->controls();
+
+  controls->set_can_detach(true);
+
+  scoped_refptr<SchedulerWorker> worker = SchedulerWorker::Create(
+      ThreadPriority::NORMAL, std::move(delegate), &task_tracker,
+      SchedulerWorker::InitialState::ALIVE);
+  worker->WakeUp();
+
+  controls->WaitForDetach();
+  worker->Cleanup();
+  worker = nullptr;
+  controls->WaitForDelegateDestroy();
+}
+
+TEST(TaskSchedulerWorkerTest, WorkerCleanupDuringWork) {
+  TaskTracker task_tracker;
+  // Will be owned by SchedulerWorker.
+  // No mock here as that's reasonably covered by other tests and the delegate
+  // may destroy on a different thread. Mocks aren't designed with that in mind.
+  std::unique_ptr<ControllableDetachDelegate> delegate =
+      MakeUnique<ControllableDetachDelegate>(&task_tracker);
+  scoped_refptr<ControllableDetachDelegate::Controls> controls =
+      delegate->controls();
+
+  controls->HaveWorkBlock();
+
+  scoped_refptr<SchedulerWorker> worker = SchedulerWorker::Create(
+      ThreadPriority::NORMAL, std::move(delegate), &task_tracker,
+      SchedulerWorker::InitialState::ALIVE);
+  worker->WakeUp();
+
+  controls->WaitForWorkToRun();
+  worker->Cleanup();
+  worker = nullptr;
+  controls->UnblockWork();
+  controls->WaitForDelegateDestroy();
+}
+
+TEST(TaskSchedulerWorkerTest, WorkerCleanupDuringWait) {
+  TaskTracker task_tracker;
+  // Will be owned by SchedulerWorker.
+  // No mock here as that's reasonably covered by other tests and the delegate
+  // may destroy on a different thread. Mocks aren't designed with that in mind.
+  std::unique_ptr<ControllableDetachDelegate> delegate =
+      MakeUnique<ControllableDetachDelegate>(&task_tracker);
+  scoped_refptr<ControllableDetachDelegate::Controls> controls =
+      delegate->controls();
+
+  scoped_refptr<SchedulerWorker> worker = SchedulerWorker::Create(
+      ThreadPriority::NORMAL, std::move(delegate), &task_tracker,
+      SchedulerWorker::InitialState::ALIVE);
+  worker->WakeUp();
+
+  controls->WaitForDetachRequest();
+  worker->Cleanup();
+  worker = nullptr;
+  controls->WaitForDelegateDestroy();
+}
+
+TEST(TaskSchedulerWorkerTest, WorkerCleanupDuringShutdown) {
+  TaskTracker task_tracker;
+  // Will be owned by SchedulerWorker.
+  // No mock here as that's reasonably covered by other tests and the delegate
+  // may destroy on a different thread. Mocks aren't designed with that in mind.
+  std::unique_ptr<ControllableDetachDelegate> delegate =
+      MakeUnique<ControllableDetachDelegate>(&task_tracker);
+  scoped_refptr<ControllableDetachDelegate::Controls> controls =
+      delegate->controls();
+
+  controls->HaveWorkBlock();
+
+  scoped_refptr<SchedulerWorker> worker = SchedulerWorker::Create(
+      ThreadPriority::NORMAL, std::move(delegate), &task_tracker,
+      SchedulerWorker::InitialState::ALIVE);
+  worker->WakeUp();
+
+  controls->WaitForWorkToRun();
+  task_tracker.Shutdown();
+  worker->Cleanup();
+  worker = nullptr;
+  controls->UnblockWork();
+  controls->WaitForDelegateDestroy();
+}
+
+namespace {
+
+class CallJoinFromDifferentThread : public SimpleThread {
+ public:
+  CallJoinFromDifferentThread(SchedulerWorker* worker_to_join)
+      : SimpleThread("SchedulerWorkerJoinThread"),
+        worker_to_join_(worker_to_join),
+        run_started_event_(WaitableEvent::ResetPolicy::MANUAL,
+                           WaitableEvent::InitialState::NOT_SIGNALED) {}
+
+  ~CallJoinFromDifferentThread() override = default;
+
+  void Run() override {
+    run_started_event_.Signal();
+    worker_to_join_->JoinForTesting();
+  }
+
+  void WaitForRunToStart() { run_started_event_.Wait(); }
+
+ private:
+  SchedulerWorker* const worker_to_join_;
+  WaitableEvent run_started_event_;
+  DISALLOW_COPY_AND_ASSIGN(CallJoinFromDifferentThread);
+};
+
+}  // namespace
+
+TEST(TaskSchedulerWorkerTest, WorkerCleanupDuringJoin) {
+  TaskTracker task_tracker;
+  // Will be owned by SchedulerWorker.
+  // No mock here as that's reasonably covered by other tests and the
+  // delegate may destroy on a different thread. Mocks aren't designed with that
+  // in mind.
+  std::unique_ptr<ControllableDetachDelegate> delegate =
+      MakeUnique<ControllableDetachDelegate>(&task_tracker);
+  scoped_refptr<ControllableDetachDelegate::Controls> controls =
+      delegate->controls();
+
+  controls->HaveWorkBlock();
+
+  scoped_refptr<SchedulerWorker> worker = SchedulerWorker::Create(
+      ThreadPriority::NORMAL, std::move(delegate), &task_tracker,
+      SchedulerWorker::InitialState::ALIVE);
+  worker->WakeUp();
+
+  controls->WaitForWorkToRun();
+  CallJoinFromDifferentThread join_from_different_thread(worker.get());
+  join_from_different_thread.Start();
+  join_from_different_thread.WaitForRunToStart();
+  // Sleep here to give the other thread a chance to call JoinForTesting().
+  // Receiving a signal that Run() was called doesn't mean JoinForTesting() was
+  // necessarily called, and we can't signal after JoinForTesting() as
+  // JoinForTesting() blocks until we call UnblockWork().
+  PlatformThread::Sleep(TestTimeouts::tiny_timeout());
+  worker->Cleanup();
+  worker = nullptr;
+  controls->UnblockWork();
+  controls->WaitForDelegateDestroy();
+  join_from_different_thread.Join();
+}
+
 TEST(TaskSchedulerWorkerTest, WorkerDetachesAndWakes) {
   TaskTracker task_tracker;
   // Will be owned by SchedulerWorker.
-  ControllableDetachDelegate* delegate =
-      new StrictMock<ControllableDetachDelegate>(&task_tracker);
-  delegate->set_can_detach(true);
+  MockedControllableDetachDelegate* delegate =
+      new StrictMock<MockedControllableDetachDelegate>(&task_tracker);
+  scoped_refptr<ControllableDetachDelegate::Controls> controls =
+      delegate->controls();
+
+  controls->set_can_detach(true);
   EXPECT_CALL(*delegate, OnMainEntry(_));
-  std::unique_ptr<SchedulerWorker> worker =
-      SchedulerWorker::Create(
-          ThreadPriority::NORMAL, WrapUnique(delegate), &task_tracker,
-          SchedulerWorker::InitialState::ALIVE);
+  scoped_refptr<SchedulerWorker> worker = SchedulerWorker::Create(
+      ThreadPriority::NORMAL, WrapUnique(delegate), &task_tracker,
+      SchedulerWorker::InitialState::ALIVE);
   worker->WakeUp();
-  delegate->WaitForWorkToRun();
+  controls->WaitForWorkToRun();
   Mock::VerifyAndClear(delegate);
-  delegate->WaitForDetachRequest();
-  delegate->WaitForDetach();
+  controls->WaitForDetachRequest();
+  controls->WaitForDetach();
   ASSERT_FALSE(worker->ThreadAliveForTesting());
 
-  delegate->ResetState();
-  delegate->set_can_detach(false);
+  controls->ResetState();
+  controls->set_can_detach(false);
   // Expect OnMainEntry() to be called when SchedulerWorker recreates its
   // thread.
   EXPECT_CALL(*delegate, OnMainEntry(worker.get()));
   worker->WakeUp();
-  delegate->WaitForWorkToRun();
+  controls->WaitForWorkToRun();
   Mock::VerifyAndClear(delegate);
-  delegate->WaitForDetachRequest();
-  delegate->WaitForDetach();
+  controls->WaitForDetachRequest();
+  controls->WaitForDetach();
   ASSERT_TRUE(worker->ThreadAliveForTesting());
   worker->JoinForTesting();
 }
@@ -486,18 +728,19 @@ TEST(TaskSchedulerWorkerTest, WorkerDetachesAndWakes) {
 TEST(TaskSchedulerWorkerTest, CreateDetached) {
   TaskTracker task_tracker;
   // Will be owned by SchedulerWorker.
-  ControllableDetachDelegate* delegate =
-      new StrictMock<ControllableDetachDelegate>(&task_tracker);
-  std::unique_ptr<SchedulerWorker> worker =
-      SchedulerWorker::Create(
-          ThreadPriority::NORMAL, WrapUnique(delegate), &task_tracker,
-          SchedulerWorker::InitialState::DETACHED);
+  MockedControllableDetachDelegate* delegate =
+      new StrictMock<MockedControllableDetachDelegate>(&task_tracker);
+  scoped_refptr<ControllableDetachDelegate::Controls> controls =
+      delegate->controls();
+  scoped_refptr<SchedulerWorker> worker = SchedulerWorker::Create(
+      ThreadPriority::NORMAL, WrapUnique(delegate), &task_tracker,
+      SchedulerWorker::InitialState::DETACHED);
   ASSERT_FALSE(worker->ThreadAliveForTesting());
   EXPECT_CALL(*delegate, OnMainEntry(worker.get()));
   worker->WakeUp();
-  delegate->WaitForWorkToRun();
+  controls->WaitForWorkToRun();
   Mock::VerifyAndClear(delegate);
-  delegate->WaitForDetachRequest();
+  controls->WaitForDetachRequest();
   ASSERT_TRUE(worker->ThreadAliveForTesting());
   worker->JoinForTesting();
 }
@@ -560,7 +803,7 @@ TEST(TaskSchedulerWorkerTest, BumpPriorityOfAliveThreadDuringShutdown) {
           ? ThreadPriority::BACKGROUND
           : ThreadPriority::NORMAL);
 
-  std::unique_ptr<SchedulerWorker> worker = SchedulerWorker::Create(
+  scoped_refptr<SchedulerWorker> worker = SchedulerWorker::Create(
       ThreadPriority::BACKGROUND, std::move(delegate), &task_tracker,
       SchedulerWorker::InitialState::ALIVE);
 
@@ -587,7 +830,7 @@ TEST(TaskSchedulerWorkerTest, BumpPriorityOfDetachedThreadDuringShutdown) {
   delegate_raw->SetExpectedThreadPriority(ThreadPriority::NORMAL);
 
   // Create a DETACHED thread.
-  std::unique_ptr<SchedulerWorker> worker = SchedulerWorker::Create(
+  scoped_refptr<SchedulerWorker> worker = SchedulerWorker::Create(
       ThreadPriority::BACKGROUND, std::move(delegate), &task_tracker,
       SchedulerWorker::InitialState::DETACHED);