blob: cf44414de49d4158c0b6d7e215f6cde448aed241 [file] [log] [blame]
// Copyright (c) 2013 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 <atomic>
#include <memory>
#include <mutex>
#include "base/base_export.h"
#include "base/compiler_specific.h"
// Spinlock is a simple spinlock class based on the standard CPU primitive of
// atomic increment and decrement of an int at a given memory address. These are
// intended only for very short duration locks and assume a system with multiple
// cores. For any potentially longer wait you should use a real lock, such as
// |base::Lock|.
// |SpinLock|s MUST be globals. Using them as (e.g.) struct/class members will
// result in an uninitialized lock, which is dangerously incorrect.
namespace base {
namespace subtle {
class SpinLock {
using Guard = std::lock_guard<SpinLock>;
ALWAYS_INLINE void lock() {
static_assert(sizeof(lock_) == sizeof(int),
"int and lock_ are different sizes");
if (LIKELY(!, std::memory_order_acquire)))
ALWAYS_INLINE void unlock() {, std::memory_order_release); }
// This is called if the initial attempt to acquire the lock fails. It's
// slower, but has a much better scheduling and power consumption behavior.
BASE_EXPORT void LockSlow();
std::atomic_int lock_;
} // namespace subtle
} // namespace base