Separate the create and start phases in SchedulerSingleThreadTaskRunnerManager.

base/task_scheduler/scheduler_single_thread_task_runner_manager_unittest.cc

 // Copyright 2017 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_single_thread_task_runner_manager.h"
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "base/synchronization/lock.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/task_scheduler/delayed_task_manager.h"
 #include "base/task_scheduler/post_task.h"
 #include "base/task_scheduler/scheduler_worker_pool_params.h"
 #include "base/task_scheduler/task_tracker.h"
 #include "base/task_scheduler/task_traits.h"
 #include "base/test/test_timeouts.h"
+#include "base/threading/platform_thread.h"
 #include "base/threading/simple_thread.h"
 #include "base/threading/thread.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #include <objbase.h>
 
 #include "base/win/current_module.h"
 #endif  // defined(OS_WIN)
@@ skipping 78 matching lines @@
   *thread_priority = PlatformThread::GetCurrentThreadPriority();
 }
 
 void ShouldNotRun() {
   ADD_FAILURE() << "Ran a task that shouldn't run.";
 }
 
 }  // namespace
 
 TEST_F(TaskSchedulerSingleThreadTaskRunnerManagerTest, DifferentThreadsUsed) {
+  single_thread_task_runner_manager_->Start();
   scoped_refptr<SingleThreadTaskRunner> task_runner_1 =
       single_thread_task_runner_manager_
           ->CreateSingleThreadTaskRunnerWithTraits(
               TaskTraits().WithShutdownBehavior(
                   TaskShutdownBehavior::BLOCK_SHUTDOWN));
   scoped_refptr<SingleThreadTaskRunner> task_runner_2 =
       single_thread_task_runner_manager_
           ->CreateSingleThreadTaskRunnerWithTraits(
               TaskTraits().WithShutdownBehavior(
                   TaskShutdownBehavior::BLOCK_SHUTDOWN));
 
   PlatformThreadRef thread_ref_1;
   task_runner_1->PostTask(FROM_HERE, Bind(&CaptureThreadRef, &thread_ref_1));
   PlatformThreadRef thread_ref_2;
   task_runner_2->PostTask(FROM_HERE, Bind(&CaptureThreadRef, &thread_ref_2));
 
   task_tracker_.Shutdown();
 
   ASSERT_FALSE(thread_ref_1.is_null());
   ASSERT_FALSE(thread_ref_2.is_null());
   EXPECT_NE(thread_ref_1, thread_ref_2);
 }
 
 TEST_F(TaskSchedulerSingleThreadTaskRunnerManagerTest, PrioritySetCorrectly) {
+  single_thread_task_runner_manager_->Start();
   // Why are events used here instead of the task tracker?
   // Shutting down can cause priorities to get raised. This means we have to use
   // events to determine when a task is run.
   scoped_refptr<SingleThreadTaskRunner> task_runner_background =
       single_thread_task_runner_manager_
           ->CreateSingleThreadTaskRunnerWithTraits(
               TaskTraits().WithPriority(TaskPriority::BACKGROUND));
   scoped_refptr<SingleThreadTaskRunner> task_runner_user_visible =
       single_thread_task_runner_manager_
           ->CreateSingleThreadTaskRunnerWithTraits(
@@ skipping 40 matching lines @@
   waitable_event_user_blocking.Wait();
 
   if (Lock::HandlesMultipleThreadPriorities())
     EXPECT_EQ(ThreadPriority::BACKGROUND, thread_priority_background);
   else
     EXPECT_EQ(ThreadPriority::NORMAL, thread_priority_background);
   EXPECT_EQ(ThreadPriority::NORMAL, thread_priority_user_visible);
   EXPECT_EQ(ThreadPriority::NORMAL, thread_priority_user_blocking);
 }
 
+// Verify that a task posted before Start() doesn't run until Start() is called.
+TEST_F(TaskSchedulerSingleThreadTaskRunnerManagerTest, PostTaskBeforeStart) {
+  bool started = false;
+  WaitableEvent task_running(WaitableEvent::ResetPolicy::MANUAL,
+                             WaitableEvent::InitialState::NOT_SIGNALED);
+  single_thread_task_runner_manager_
+      ->CreateSingleThreadTaskRunnerWithTraits(TaskTraits())
+      ->PostTask(FROM_HERE,
+                 Bind(
+                     [](WaitableEvent* task_running, bool* started) {
+                       task_running->Signal();
+
+                       // The task should not run before Start().
+                       EXPECT_TRUE(*started);
+                     },
+                     Unretained(&task_running), Unretained(&started)));
+
+  // Wait a little bit to make sure that the task isn't scheduled before start.
+  // Note: This test won't catch a case where the task is scheduled between
+  // setting |start| and calling Start(). However, we expect the test to be
+  // flaky if the tested code allows that to happen.
+  PlatformThread::Sleep(TestTimeouts::tiny_timeout());
+  started = true;

[gab, 2017/04/10 18:04:56]

Need to use AtomicFlag or this a data race (no such thing as a "benign data
race":
https://software.intel.com/en-us/blogs/2013/01/06/benign-data-races-what-coul...)

[fdoray, 2017/04/10 19:05:00]

Done.

+  single_thread_task_runner_manager_->Start();
+
+  // This should not hang if the task is scheduled after Start().
+  task_running.Wait();
+}
+
 TEST_F(TaskSchedulerSingleThreadTaskRunnerManagerTest, PostTaskAfterShutdown) {
+  single_thread_task_runner_manager_->Start();
   auto task_runner = single_thread_task_runner_manager_
                          ->CreateSingleThreadTaskRunnerWithTraits(TaskTraits());
   task_tracker_.Shutdown();
   EXPECT_FALSE(task_runner->PostTask(FROM_HERE, Bind(&ShouldNotRun)));
 }
 
 // Verify that a Task runs shortly after its delay expires.
 TEST_F(TaskSchedulerSingleThreadTaskRunnerManagerTest, PostDelayedTask) {
+  single_thread_task_runner_manager_->Start();
   TimeTicks start_time = TimeTicks::Now();
 
   // Post a task with a short delay.
   WaitableEvent task_ran(WaitableEvent::ResetPolicy::MANUAL,
                          WaitableEvent::InitialState::NOT_SIGNALED);
   auto task_runner = single_thread_task_runner_manager_
                          ->CreateSingleThreadTaskRunnerWithTraits(TaskTraits());
   EXPECT_TRUE(task_runner->PostDelayedTask(
       FROM_HERE, Bind(&WaitableEvent::Signal, Unretained(&task_ran)),
       TestTimeouts::tiny_timeout()));
 
   // Wait until the task runs.
   task_ran.Wait();
 
   // Expect the task to run after its delay expires, but not more than 250 ms
   // after that.
   const TimeDelta actual_delay = TimeTicks::Now() - start_time;
   EXPECT_GE(actual_delay, TestTimeouts::tiny_timeout());
   EXPECT_LT(actual_delay,
             TimeDelta::FromMilliseconds(250) + TestTimeouts::tiny_timeout());
 }
 
 TEST_F(TaskSchedulerSingleThreadTaskRunnerManagerTest,
        RunsTasksOnCurrentThread) {
+  single_thread_task_runner_manager_->Start();
   scoped_refptr<SingleThreadTaskRunner> task_runner_1 =
       single_thread_task_runner_manager_
           ->CreateSingleThreadTaskRunnerWithTraits(
               TaskTraits().WithShutdownBehavior(
                   TaskShutdownBehavior::BLOCK_SHUTDOWN));
   scoped_refptr<SingleThreadTaskRunner> task_runner_2 =
       single_thread_task_runner_manager_
           ->CreateSingleThreadTaskRunnerWithTraits(
               TaskTraits().WithShutdownBehavior(
                   TaskShutdownBehavior::BLOCK_SHUTDOWN));
@@ skipping 61 matching lines @@
     single_thread_task_runner_manager_.reset();
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TaskSchedulerSingleThreadTaskRunnerManagerJoinTest);
 };
 
 }  // namespace
 
 TEST_F(TaskSchedulerSingleThreadTaskRunnerManagerJoinTest, ConcurrentJoin) {
+  single_thread_task_runner_manager_->Start();
   // Exercises the codepath where the workers are unavailable for unregistration
   // because of a Join call.
   WaitableEvent task_running(WaitableEvent::ResetPolicy::MANUAL,
                              WaitableEvent::InitialState::NOT_SIGNALED);
   WaitableEvent task_blocking(WaitableEvent::ResetPolicy::MANUAL,
                               WaitableEvent::InitialState::NOT_SIGNALED);
 
   {
     auto task_runner = single_thread_task_runner_manager_
                            ->CreateSingleThreadTaskRunnerWithTraits(
                                TaskTraits().WithBaseSyncPrimitives());
     EXPECT_TRUE(task_runner->PostTask(
         FROM_HERE, Bind(&WaitableEvent::Signal, Unretained(&task_running))));
     EXPECT_TRUE(task_runner->PostTask(
         FROM_HERE, Bind(&WaitableEvent::Wait, Unretained(&task_blocking))));
   }
 
   task_running.Wait();
   CallJoinFromDifferentThread join_from_different_thread(
       single_thread_task_runner_manager_.get());
   join_from_different_thread.Start();
   join_from_different_thread.WaitForRunToStart();
   task_blocking.Signal();
   join_from_different_thread.Join();
 }
 
 TEST_F(TaskSchedulerSingleThreadTaskRunnerManagerJoinTest,
        ConcurrentJoinExtraSkippedTask) {
+  single_thread_task_runner_manager_->Start();
   // Tests to make sure that tasks are properly cleaned up at Join, allowing
   // SingleThreadTaskRunners to unregister themselves.
   WaitableEvent task_running(WaitableEvent::ResetPolicy::MANUAL,
                              WaitableEvent::InitialState::NOT_SIGNALED);
   WaitableEvent task_blocking(WaitableEvent::ResetPolicy::MANUAL,
                               WaitableEvent::InitialState::NOT_SIGNALED);
 
   {
     auto task_runner = single_thread_task_runner_manager_
                            ->CreateSingleThreadTaskRunnerWithTraits(
@@ skipping 10 matching lines @@
       single_thread_task_runner_manager_.get());
   join_from_different_thread.Start();
   join_from_different_thread.WaitForRunToStart();
   task_blocking.Signal();
   join_from_different_thread.Join();
 }
 
 #if defined(OS_WIN)
 
 TEST_F(TaskSchedulerSingleThreadTaskRunnerManagerTest, COMSTAInitialized) {
+  single_thread_task_runner_manager_->Start();
   scoped_refptr<SingleThreadTaskRunner> com_task_runner =
       single_thread_task_runner_manager_->CreateCOMSTATaskRunnerWithTraits(
           TaskTraits().WithShutdownBehavior(
               TaskShutdownBehavior::BLOCK_SHUTDOWN));
 
   com_task_runner->PostTask(
       FROM_HERE, Bind([]() {
         HRESULT hr = CoInitializeEx(nullptr, COINIT_MULTITHREADED);
         if (SUCCEEDED(hr)) {
           ADD_FAILURE() << "COM STA was not initialized on this thread";
@@ skipping 43 matching lines @@
   }
 
   bool register_class_succeeded_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(TaskSchedulerSingleThreadTaskRunnerManagerTestWin);
 };
 
 }  // namespace
 
 TEST_F(TaskSchedulerSingleThreadTaskRunnerManagerTestWin, PumpsMessages) {
+  single_thread_task_runner_manager_->Start();
   scoped_refptr<SingleThreadTaskRunner> com_task_runner =
       single_thread_task_runner_manager_->CreateCOMSTATaskRunnerWithTraits(
           TaskTraits().WithShutdownBehavior(
               TaskShutdownBehavior::BLOCK_SHUTDOWN));
   HWND hwnd = nullptr;
   // HWNDs process messages on the thread that created them, so we have to
   // create them within the context of the task runner to properly simulate a
   // COM callback.
   com_task_runner->PostTask(
       FROM_HERE,
@@ skipping 11 matching lines @@
   com_task_runner->PostTask(
       FROM_HERE, Bind([](HWND hwnd) { ::DestroyWindow(hwnd); }, hwnd));
 
   task_tracker_.Shutdown();
 }
 
 #endif  // defined(OS_WIN)
 
 }  // namespace internal
 }  // namespace base