Makes HandleWatcher block until no longer waiting on pipe

mojo/common/handle_watcher_unittest.cc

Index: mojo/common/handle_watcher_unittest.cc
diff --git a/mojo/common/handle_watcher_unittest.cc b/mojo/common/handle_watcher_unittest.cc
index 02cc6105d6a2bf9fcfe4c2311e62f3241e6c5978..e28397e2c9dda021ca7046fd2f06d4a3e2b96531 100644
--- a/mojo/common/handle_watcher_unittest.cc
+++ b/mojo/common/handle_watcher_unittest.cc
@@ -9,8 +9,10 @@
 #include "base/at_exit.h"
 #include "base/auto_reset.h"
 #include "base/bind.h"
+#include "base/memory/scoped_vector.h"
 #include "base/run_loop.h"
 #include "base/test/simple_test_tick_clock.h"
+#include "base/threading/thread.h"
 #include "mojo/common/time_helper.h"
 #include "mojo/public/cpp/system/core.h"
 #include "mojo/public/cpp/test_support/test_utils.h"
@@ -336,6 +338,100 @@ TEST(HandleWatcherCleanEnvironmentTest, AbortedOnMessageLoopDestruction) {
   EXPECT_EQ(MOJO_RESULT_ABORTED, result);
 }
 
+void NeverReached(MojoResult result) {
+  FAIL() << "Callback should never be invoked " << result;
+}
+
+// Called on the main thread when a thread is done. Decrements |active_count|
+// and if |active_count| is zero quits |run_loop|.
+void StressThreadDone(base::RunLoop* run_loop, int* active_count) {
+  (*active_count)--;
+  EXPECT_GE(*active_count, 0);
+  if (*active_count == 0)
+    run_loop->Quit();
+}
+
+// See description of StressTest. This is called on the background thread.
+// |count| is the number of HandleWatchers to create. |active_count| is the
+// number of outstanding threads, |task_runner| the task runner for the main
+// thread and |run_loop| the run loop that should be quit when there are no more
+// threads running. When done StressThreadDone() is invoked on the main thread.
+// |active_count| and |run_loop| should only be used on the main thread.
+void RunStressTest(int count,
+                   scoped_refptr<base::TaskRunner> task_runner,
+                   base::RunLoop* run_loop,
+                   int* active_count) {
+  struct TestData {
+    MessagePipe pipe;
+    HandleWatcher watcher;
+  };
+  ScopedVector<TestData> data_vector;
+  for (int i = 0; i < count; ++i) {
+    if (i % 20 == 0) {
+      // Every so often we wait. This results in some level of thread balancing
+      // as well as making sure HandleWatcher has time to actually start some
+      // watches.
+      MessagePipe test_pipe;
+      ASSERT_TRUE(test_pipe.handle0.is_valid());
+      CallbackHelper callback_helper;
+      HandleWatcher watcher;
+      callback_helper.Start(&watcher, test_pipe.handle0.get());
+      RunUntilIdle();
+      EXPECT_FALSE(callback_helper.got_callback());
+      EXPECT_TRUE(mojo::test::WriteTextMessage(test_pipe.handle1.get(),
+                                               std::string()));
+      base::MessageLoop::ScopedNestableTaskAllower scoper(
+          base::MessageLoop::current());
+      callback_helper.RunUntilGotCallback();
+      EXPECT_TRUE(callback_helper.got_callback());
+    } else {
+      scoped_ptr<TestData> test_data(new TestData);
+      ASSERT_TRUE(test_data->pipe.handle0.is_valid());
+      test_data->watcher.Start(test_data->pipe.handle0.get(),
+                    MOJO_HANDLE_SIGNAL_READABLE,
+                    MOJO_DEADLINE_INDEFINITE,
+                    base::Bind(&NeverReached));
+      data_vector.push_back(test_data.release());
+    }
+    if (i % 15 == 0)
+      data_vector.clear();
+  }
+  task_runner->PostTask(FROM_HERE,
+                        base::Bind(&StressThreadDone, run_loop,
+                                   active_count));
+}
+
+// This test is meant to stress HandleWatcher. It uses from various threads
+// repeatedly starting and stopping watches. It spins up kThreadCount
+// threads. Each thread creates kWatchCount watches. Every so often each thread
+// writes to a pipe and waits for the response.
+TEST(HandleWatcherCleanEnvironmentTest, StressTest) {
+#if defined(NDEBUG)
+  const int kThreadCount = 15;
+  const int kWatchCount = 400;
+#else
+  const int kThreadCount = 10;
+  const int kWatchCount = 250;
+#endif
+
+  base::ShadowingAtExitManager at_exit;
+  base::MessageLoop message_loop;
+  base::RunLoop run_loop;
+  ScopedVector<base::Thread> threads;
+  int threads_active_counter = kThreadCount;
+  for (int i = 0; i < kThreadCount; ++i) {
+    scoped_ptr<base::Thread> thread(new base::Thread("test thread"));
+    thread->Start();
+    thread->task_runner()->PostTask(

[darin (slow to review), 2014/07/22 17:42:57]

you might consider starting all of the threads, and then separately looping over
the threads to post the RunStressTest task. that may help encourage more
overlapping.

[sky, 2014/07/22 18:20:50]

Done.

+        FROM_HERE, base::Bind(&RunStressTest, kWatchCount,
+                              message_loop.task_runner(),
+                              &run_loop, &threads_active_counter));
+    threads.push_back(thread.release());
+  }
+  run_loop.Run();
+  ASSERT_EQ(0, threads_active_counter);
+}
+
 }  // namespace test
 }  // namespace common
 }  // namespace mojo