Revert 146792 - Lock-free GamepadSeqLock (try 2)

content/common/gamepad_seqlock_unittest.cc

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// 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<TestData>* seqlock,
+      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;
-      seqlock_->ReadTo(&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<TestData>* seqlock_;
+  content::GamepadSeqLock* seqlock_;
+  TestData* data_;
   base::AtomicRefCount* ready_;
 
   DISALLOW_COPY_AND_ASSIGN(BasicSeqLockTestThread);
 };
 
 TEST(GamepadSeqLockTest, ManyThreads) {
-  content::GamepadSeqLock<TestData> seqlock;
+  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, &ready);
+    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.Write(data);
+    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