sync/internal_api/public/base/cancelation_signal_unittest.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "sync/internal_api/public/base/cancelation_signal.h"
   6
   7 #include "base/bind.h"
   8 #include "base/message_loop/message_loop.h"
   9 #include "base/synchronization/waitable_event.h"
  10 #include "base/threading/platform_thread.h"
  11 #include "base/threading/thread.h"
  12 #include "base/time/time.h"
  13 #include "sync/internal_api/public/base/cancelation_observer.h"
  14 #include "testing/gtest/include/gtest/gtest.h"
  15
  16 namespace syncer {
  17
  18 class BlockingTask : public CancelationObserver {
  19  public:
  20   BlockingTask(CancelationSignal* cancel_signal);
  21   ~BlockingTask() override;
  22
  23   // Starts the |exec_thread_| and uses it to execute DoRun().
  24   void RunAsync(base::WaitableEvent* task_start_signal,
  25                 base::WaitableEvent* task_done_signal);
  26
  27   // Blocks until canceled.  Signals |task_done_signal| when finished (either
  28   // via early cancel or cancel after start).  Signals |task_start_signal| if
  29   // and when the task starts successfully (which will not happen if the task
  30   // was cancelled early).
  31   void Run(base::WaitableEvent* task_start_signal,
  32            base::WaitableEvent* task_done_signal);
  33
  34   // Implementation of CancelationObserver.
  35   // Wakes up the thread blocked in Run().
  36   void OnSignalReceived() override;
  37
  38   // Checks if we ever did successfully start waiting for |event_|.  Be careful
  39   // with this.  The flag itself is thread-unsafe, and the event that flips it
  40   // is racy.
  41   bool WasStarted();
  42
  43  private:
  44   base::WaitableEvent event_;
  45   base::Thread exec_thread_;
  46   CancelationSignal* cancel_signal_;
  47   bool was_started_;
  48 };
  49
  50 BlockingTask::BlockingTask(CancelationSignal* cancel_signal)
  51   : event_(true, false),
  52     exec_thread_("BlockingTaskBackgroundThread"),
  53     cancel_signal_(cancel_signal),
  54     was_started_(false) { }
  55
  56 BlockingTask::~BlockingTask() {
  57   if (was_started_) {
  58     cancel_signal_->UnregisterHandler(this);
  59   }
  60 }
  61
  62 void BlockingTask::RunAsync(base::WaitableEvent* task_start_signal,
  63                             base::WaitableEvent* task_done_signal) {
  64   exec_thread_.Start();
  65   exec_thread_.message_loop()->PostTask(
  66       FROM_HERE,
  67       base::Bind(&BlockingTask::Run,
  68                  base::Unretained(this),
  69                  base::Unretained(task_start_signal),
  70                  base::Unretained(task_done_signal)));
  71 }
  72
  73 void BlockingTask::Run(
  74     base::WaitableEvent* task_start_signal,
  75     base::WaitableEvent* task_done_signal) {
  76   if (cancel_signal_->TryRegisterHandler(this)) {
  77     DCHECK(!event_.IsSignaled());
  78     was_started_ = true;
  79     task_start_signal->Signal();
  80     event_.Wait();
  81   }
  82   task_done_signal->Signal();
  83 }
  84
  85 void BlockingTask::OnSignalReceived() {
  86   event_.Signal();
  87 }
  88
  89 bool BlockingTask::WasStarted() {
  90   return was_started_;
  91 }
  92
  93 class CancelationSignalTest : public ::testing::Test {
  94  public:
  95   CancelationSignalTest();
  96   ~CancelationSignalTest() override;
  97
  98   // Starts the blocking task on a background thread.  Does not wait for the
  99   // task to start.
 100   void StartBlockingTaskAsync();
 101
 102   // Starts the blocking task on a background thread.  Does not return until
 103   // the task has been started.
 104   void StartBlockingTaskAndWaitForItToStart();
 105
 106   // Cancels the blocking task.
 107   void CancelBlocking();
 108
 109   // Verifies that the background task was canceled early.
 110   //
 111   // This method may block for a brief period of time while waiting for the
 112   // background thread to make progress.
 113   bool VerifyTaskNotStarted();
 114
 115  private:
 116   base::MessageLoop main_loop_;
 117
 118   CancelationSignal signal_;
 119   base::WaitableEvent task_start_event_;
 120   base::WaitableEvent task_done_event_;
 121   BlockingTask blocking_task_;
 122 };
 123
 124 CancelationSignalTest::CancelationSignalTest()
 125   : task_start_event_(false, false),
 126     task_done_event_(false, false),
 127     blocking_task_(&signal_) {}
 128
 129 CancelationSignalTest::~CancelationSignalTest() {}
 130
 131 void CancelationSignalTest::StartBlockingTaskAsync() {
 132   blocking_task_.RunAsync(&task_start_event_, &task_done_event_);
 133 }
 134
 135 void CancelationSignalTest::StartBlockingTaskAndWaitForItToStart() {
 136   blocking_task_.RunAsync(&task_start_event_, &task_done_event_);
 137   task_start_event_.Wait();
 138 }
 139
 140 void CancelationSignalTest::CancelBlocking() {
 141   signal_.Signal();
 142 }
 143
 144 bool CancelationSignalTest::VerifyTaskNotStarted() {
 145   // Wait until BlockingTask::Run() has finished.
 146   task_done_event_.Wait();
 147
 148   // Verify the background thread never started blocking.
 149   return !blocking_task_.WasStarted();
 150 }
 151
 152 class FakeCancelationObserver : public CancelationObserver {
 153   void OnSignalReceived() override {}
 154 };
 155
 156 TEST(CancelationSignalTest_SingleThread, CheckFlags) {
 157   FakeCancelationObserver observer;
 158   CancelationSignal signal;
 159
 160   EXPECT_FALSE(signal.IsSignalled());
 161   signal.Signal();
 162   EXPECT_TRUE(signal.IsSignalled());
 163   EXPECT_FALSE(signal.TryRegisterHandler(&observer));
 164 }
 165
 166 // Send the cancelation signal before the task is started.  This will ensure
 167 // that the task will never be "started" (ie. TryRegisterHandler() will fail,
 168 // so it will never start blocking on its main WaitableEvent).
 169 TEST_F(CancelationSignalTest, CancelEarly) {
 170   CancelBlocking();
 171   StartBlockingTaskAsync();
 172   EXPECT_TRUE(VerifyTaskNotStarted());
 173 }
 174
 175 // Send the cancelation signal after the task has started running.  This tests
 176 // the non-early exit code path, where the task is stopped while it is in
 177 // progress.
 178 TEST_F(CancelationSignalTest, Cancel) {
 179   StartBlockingTaskAndWaitForItToStart();
 180
 181   // Wait for the task to finish and let verify it has been started.
 182   CancelBlocking();
 183   EXPECT_FALSE(VerifyTaskNotStarted());
 184 }
 185
 186 }  // namespace syncer