Revert 146792 - Lock-free GamepadSeqLock (try 2)

content/browser/gamepad/gamepad_provider_unittest.cc

 // Copyright (c) 2012 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/memory/scoped_ptr.h"
 #include "base/process_util.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/system_monitor/system_monitor.h"
-#include "base/threading/platform_thread.h"
 #include "content/browser/gamepad/data_fetcher.h"
 #include "content/browser/gamepad/gamepad_provider.h"
 #include "content/common/gamepad_hardware_buffer.h"
 #include "content/common/gamepad_messages.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebGamepads.h"
 
 namespace content {
 
 namespace {
 
 using WebKit::WebGamepads;
 
 class MockDataFetcher : public GamepadDataFetcher {
  public:
   explicit MockDataFetcher(const WebGamepads& test_data)
-      : test_data_(test_data) {
+      : test_data_(test_data),
+        read_data_(false, false) {
   }
   virtual void GetGamepadData(WebGamepads* pads,
                               bool devices_changed_hint) OVERRIDE {
     *pads = test_data_;
+    read_data_.Signal();
   }
 
+  void WaitForDataRead() { return read_data_.Wait(); }
+
   WebGamepads test_data_;
+  base::WaitableEvent read_data_;
 };
 
 // Main test fixture
 class GamepadProviderTest : public testing::Test {
  public:
   GamepadProvider* CreateProvider(const WebGamepads& test_data) {
 #if defined(OS_MACOSX)
     base::SystemMonitor::AllocateSystemIOPorts();
 #endif
     system_monitor_.reset(new base::SystemMonitor);
@@ skipping 22 matching lines @@
   test_data.items[0].buttonsLength = 1;
   test_data.items[0].axesLength = 2;
   test_data.items[0].buttons[0] = 1.f;
   test_data.items[0].axes[0] = -1.f;
   test_data.items[0].axes[1] = .5f;
 
   GamepadProvider* provider = CreateProvider(test_data);
 
   main_message_loop_.RunAllPending();
 
+  mock_data_fetcher_->WaitForDataRead();
+
   // Renderer-side, pull data out of poll buffer.
   base::SharedMemoryHandle handle =
       provider->GetRendererSharedMemoryHandle(base::GetCurrentProcessHandle());
   scoped_ptr<base::SharedMemory> shared_memory(
       new base::SharedMemory(handle, true));
   EXPECT_TRUE(shared_memory->Map(sizeof(GamepadHardwareBuffer)));
   void* mem = shared_memory->memory();
 
   GamepadHardwareBuffer* hwbuf = static_cast<GamepadHardwareBuffer*>(mem);
+  // See gamepad_hardware_buffer.h for details on the read discipline.
   WebGamepads output;
-  output.length = 0;
-  for (;;) {
-    hwbuf->gamepads.ReadTo(&output);
-    if (output.length == 1)
-      break;
-    base::PlatformThread::YieldCurrentThread();
-  }
+
+  base::subtle::Atomic32 version;
+  do {
+    version = hwbuf->sequence.ReadBegin();
+    memcpy(&output, &hwbuf->buffer, sizeof(output));
+  } while (hwbuf->sequence.ReadRetry(version));
+
   EXPECT_EQ(1u, output.length);
   EXPECT_EQ(1u, output.items[0].buttonsLength);
   EXPECT_EQ(1.f, output.items[0].buttons[0]);
   EXPECT_EQ(2u, output.items[0].axesLength);
   EXPECT_EQ(-1.f, output.items[0].axes[0]);
   EXPECT_EQ(0.5f, output.items[0].axes[1]);
 }
 
 }  // namespace
 
 }  // namespace content