Bring back lost gamepad_seqlock_unittest.

content/common/gamepad_seqlock_unittest.cc

-// Copyright (c) 2011 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 "content/common/gamepad_seqlock.h"
-
-#include <stdlib.h>
-
-#include "base/atomic_ref_count.h"
-#include "base/threading/platform_thread.h"
-#include "base/third_party/dynamic_annotations/dynamic_annotations.h"
-#include "testing/gtest/include/gtest/gtest.h"
-
-namespace base {
-
-// Basic test to make sure that basic operation works correctly.
-
-struct TestData {
-  unsigned a, b, c;
-};
-
-class BasicSeqLockTestThread : public PlatformThread::Delegate {
- public:
-  BasicSeqLockTestThread() {}
-
-  void Init(
-      content::GamepadSeqLock* seqlock,
-      TestData* data,
-      base::subtle::Atomic32* ready) {
-    seqlock_ = seqlock;
-    data_ = data;
-    ready_ = ready;
-  }
-  virtual void ThreadMain() {
-    while (AtomicRefCountIsZero(ready_)) {
-      PlatformThread::YieldCurrentThread();
-    }
-
-    for (unsigned i = 0; i < 1000; ++i) {
-      TestData copy;
-      base::subtle::Atomic32 version;
-      do {
-        version = seqlock_->ReadBegin();
-        copy = *data_;
-      } while (seqlock_->ReadRetry(version));
-
-      EXPECT_EQ(copy.a + 100, copy.b);
-      EXPECT_EQ(copy.c, copy.b + copy.a);
-    }
-
-    AtomicRefCountDec(ready_);
-  }
-
- private:
-  content::GamepadSeqLock* seqlock_;
-  TestData* data_;
-  base::AtomicRefCount* ready_;
-
-  DISALLOW_COPY_AND_ASSIGN(BasicSeqLockTestThread);
-};
-
-TEST(GamepadSeqLockTest, ManyThreads) {
-  content::GamepadSeqLock seqlock;
-  TestData data = { 0, 0, 0 };
-  base::AtomicRefCount ready = 0;
-
-  ANNOTATE_BENIGN_RACE_SIZED(&data, sizeof(data), "Racey reads are discarded");
-
-  static const unsigned kNumReaderThreads = 10;
-  BasicSeqLockTestThread threads[kNumReaderThreads];
-  PlatformThreadHandle handles[kNumReaderThreads];
-
-  for (unsigned i = 0; i < kNumReaderThreads; ++i)
-    threads[i].Init(&seqlock, &data, &ready);
-  for (unsigned i = 0; i < kNumReaderThreads; ++i)
-    ASSERT_TRUE(PlatformThread::Create(0, &threads[i], &handles[i]));
-
-  // The main thread is the writer, and the spawned are readers.
-  unsigned counter = 0;
-  for (;;) {
-    seqlock.WriteBegin();
-    data.a = counter++;
-    data.b = data.a + 100;
-    data.c = data.b + data.a;
-    seqlock.WriteEnd();
-
-    if (counter == 1)
-      base::AtomicRefCountIncN(&ready, kNumReaderThreads);
-
-    if (AtomicRefCountIsZero(&ready))
-      break;
-  }
-
-  for (unsigned i = 0; i < kNumReaderThreads; ++i)
-    PlatformThread::Join(handles[i]);
-}
-
-}  // namespace base