Move Source/WTF/wtf to Source/wtf

Source/WTF/wtf/TCSpinLock.h

-// Copyright (c) 2005, 2006, Google Inc.
-// Copyright (c) 2010, Patrick Gansterer <paroga@paroga.com>
-// 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 with the
-// distribution.
-//     * Neither the name of Google Inc. nor the names of its
-// contributors may be used to endorse or promote products derived from
-// this software without specific prior written permission.
-// 
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-// ---
-// Author: Sanjay Ghemawat <opensource@google.com>
-
-#ifndef TCMALLOC_INTERNAL_SPINLOCK_H__
-#define TCMALLOC_INTERNAL_SPINLOCK_H__
-
-#include <wtf/Atomics.h>
-#if OS(UNIX)
-#include <sched.h>
-#endif
-
-#if ENABLE(COMPARE_AND_SWAP)
-
-static void TCMalloc_SlowLock(unsigned* lockword);
-
-// The following is a struct so that it can be initialized at compile time
-struct TCMalloc_SpinLock {
-    void Lock() {
-      if (!WTF::weakCompareAndSwap(&lockword_, 0, 1))
-        TCMalloc_SlowLock(&lockword_);
-      WTF::memoryBarrierAfterLock();
-    }
-
-    void Unlock() {
-      WTF::memoryBarrierBeforeUnlock();
-      lockword_ = 0;
-    }
-
-    // Report if we think the lock can be held by this thread.
-    // When the lock is truly held by the invoking thread
-    // we will always return true.
-    // Indended to be used as CHECK(lock.IsHeld());
-    bool IsHeld() const {
-        return lockword_ != 0;
-    }
-
-    void Init() { lockword_ = 0; }
-    void Finalize() { }
-
-    unsigned lockword_;
-};
-
-#define SPINLOCK_INITIALIZER { 0 }
-
-static void TCMalloc_SlowLock(unsigned* lockword) {
-  do {
-#if OS(WINDOWS)
-    Sleep(0);
-#else
-    sched_yield();
-#endif
-  } while (!WTF::weakCompareAndSwap(lockword, 0, 1));
-}
-
-#else
-
-#include <pthread.h>
-
-// Portable version
-struct TCMalloc_SpinLock {
-  pthread_mutex_t private_lock_;
-
-  inline void Init() {
-    if (pthread_mutex_init(&private_lock_, NULL) != 0) CRASH();
-  }
-  inline void Finalize() {
-    if (pthread_mutex_destroy(&private_lock_) != 0) CRASH();
-  }
-  inline void Lock() {
-    if (pthread_mutex_lock(&private_lock_) != 0) CRASH();
-  }
-  inline void Unlock() {
-    if (pthread_mutex_unlock(&private_lock_) != 0) CRASH();
-  }
-  bool IsHeld() {
-    if (pthread_mutex_trylock(&private_lock_))
-      return true;
-
-    Unlock();
-    return false;
-  }
-};
-
-#define SPINLOCK_INITIALIZER { PTHREAD_MUTEX_INITIALIZER }
-
-#endif
-
-// Corresponding locker object that arranges to acquire a spinlock for
-// the duration of a C++ scope.
-class TCMalloc_SpinLockHolder {
- private:
-  TCMalloc_SpinLock* lock_;
- public:
-  inline explicit TCMalloc_SpinLockHolder(TCMalloc_SpinLock* l)
-    : lock_(l) { l->Lock(); }
-  inline ~TCMalloc_SpinLockHolder() { lock_->Unlock(); }
-};
-
-// Short-hands for convenient use by tcmalloc.cc
-typedef TCMalloc_SpinLock SpinLock;
-typedef TCMalloc_SpinLockHolder SpinLockHolder;
-
-#endif  // TCMALLOC_INTERNAL_SPINLOCK_H__