Source/wtf/TCSpinLock.h

// Copyright (c) 2005, 2006, Google Inc.
// Copyright (c) 2010, Patrick Gansterer <paroga@paroga.com>
// All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
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// in the documentation and/or other materials provided with the
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// ---
// Author: Sanjay Ghemawat <opensource@google.com>

#ifndef TCMALLOC_INTERNAL_SPINLOCK_H__
#define TCMALLOC_INTERNAL_SPINLOCK_H__

#if OS(POSIX)
#include <sched.h>
#endif

#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 }

// 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__