Revert the latest set of platform changes.

src/platform-win32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1687 matching lines @@
 }
 
 
 
 void Thread::YieldCPU() {
   Sleep(0);
 }
 
 
 // ----------------------------------------------------------------------------
+// Win32 mutex support.
+//
+// On Win32 mutexes are implemented using CRITICAL_SECTION objects. These are
+// faster than Win32 Mutex objects because they are implemented using user mode
+// atomic instructions. Therefore we only do ring transitions if there is lock
+// contention.
+
+class Win32Mutex : public Mutex {
+ public:
+  Win32Mutex() { InitializeCriticalSection(&cs_); }
+
+  virtual ~Win32Mutex() { DeleteCriticalSection(&cs_); }
+
+  virtual int Lock() {
+    EnterCriticalSection(&cs_);
+    return 0;
+  }
+
+  virtual int Unlock() {
+    LeaveCriticalSection(&cs_);
+    return 0;
+  }
+
+
+  virtual bool TryLock() {
+    // Returns non-zero if critical section is entered successfully entered.
+    return TryEnterCriticalSection(&cs_);
+  }
+
+ private:
+  CRITICAL_SECTION cs_;  // Critical section used for mutex
+};
+
+
+Mutex* OS::CreateMutex() {
+  return new Win32Mutex();
+}
+
+
+// ----------------------------------------------------------------------------
 // Win32 semaphore support.
 //
 // On Win32 semaphores are implemented using Win32 Semaphore objects. The
 // semaphores are anonymous. Also, the semaphores are initialized to have
 // no upper limit on count.
 
 
 class Win32Semaphore : public Semaphore {
  public:
   explicit Win32Semaphore(int count) {
@@ skipping 222 matching lines @@
 
 
 void OS::SetUp() {
   // Seed the random number generator.
   // Convert the current time to a 64-bit integer first, before converting it
   // to an unsigned. Going directly can cause an overflow and the seed to be
   // set to all ones. The seed will be identical for different instances that
   // call this setup code within the same millisecond.
   uint64_t seed = static_cast<uint64_t>(TimeCurrentMillis());
   srand(static_cast<unsigned int>(seed));
-  limit_mutex = new Mutex;
+  limit_mutex = CreateMutex();
 }
 
 
 void OS::TearDown() {
   delete limit_mutex;
 }
 
 
 } }  // namespace v8::internal