diff options
Diffstat (limited to 'security/sandbox/chromium/base/atomicops.h')
| -rw-r--r-- | security/sandbox/chromium/base/atomicops.h | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/security/sandbox/chromium/base/atomicops.h b/security/sandbox/chromium/base/atomicops.h new file mode 100644 index 0000000000..429e2457fc --- /dev/null +++ b/security/sandbox/chromium/base/atomicops.h @@ -0,0 +1,150 @@ +// Copyright (c) 2012 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. + +// For atomic operations on reference counts, see atomic_refcount.h. +// For atomic operations on sequence numbers, see atomic_sequence_num.h. + +// The routines exported by this module are subtle. If you use them, even if +// you get the code right, it will depend on careful reasoning about atomicity +// and memory ordering; it will be less readable, and harder to maintain. If +// you plan to use these routines, you should have a good reason, such as solid +// evidence that performance would otherwise suffer, or there being no +// alternative. You should assume only properties explicitly guaranteed by the +// specifications in this file. You are almost certainly _not_ writing code +// just for the x86; if you assume x86 semantics, x86 hardware bugs and +// implementations on other archtectures will cause your code to break. If you +// do not know what you are doing, avoid these routines, and use a Mutex. +// +// It is incorrect to make direct assignments to/from an atomic variable. +// You should use one of the Load or Store routines. The NoBarrier +// versions are provided when no barriers are needed: +// NoBarrier_Store() +// NoBarrier_Load() +// Although there are currently no compiler enforcement, you are encouraged +// to use these. +// + +#ifndef BASE_ATOMICOPS_H_ +#define BASE_ATOMICOPS_H_ + +#include <stdint.h> + +// Small C++ header which defines implementation specific macros used to +// identify the STL implementation. +// - libc++: captures __config for _LIBCPP_VERSION +// - libstdc++: captures bits/c++config.h for __GLIBCXX__ +#include <cstddef> + +#include "base/base_export.h" +#include "build/build_config.h" + +namespace base { +namespace subtle { + +typedef int32_t Atomic32; +#ifdef ARCH_CPU_64_BITS +// We need to be able to go between Atomic64 and AtomicWord implicitly. This +// means Atomic64 and AtomicWord should be the same type on 64-bit. +#if defined(__ILP32__) || defined(OS_NACL) +// NaCl's intptr_t is not actually 64-bits on 64-bit! +// http://code.google.com/p/nativeclient/issues/detail?id=1162 +typedef int64_t Atomic64; +#else +typedef intptr_t Atomic64; +#endif +#endif + +// Use AtomicWord for a machine-sized pointer. It will use the Atomic32 or +// Atomic64 routines below, depending on your architecture. +typedef intptr_t AtomicWord; + +// Atomically execute: +// result = *ptr; +// if (*ptr == old_value) +// *ptr = new_value; +// return result; +// +// I.e., replace "*ptr" with "new_value" if "*ptr" used to be "old_value". +// Always return the old value of "*ptr" +// +// This routine implies no memory barriers. +Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr, + Atomic32 old_value, + Atomic32 new_value); + +// Atomically store new_value into *ptr, returning the previous value held in +// *ptr. This routine implies no memory barriers. +Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, Atomic32 new_value); + +// Atomically increment *ptr by "increment". Returns the new value of +// *ptr with the increment applied. This routine implies no memory barriers. +Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, Atomic32 increment); + +Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr, + Atomic32 increment); + +// These following lower-level operations are typically useful only to people +// implementing higher-level synchronization operations like spinlocks, +// mutexes, and condition-variables. They combine CompareAndSwap(), a load, or +// a store with appropriate memory-ordering instructions. "Acquire" operations +// ensure that no later memory access can be reordered ahead of the operation. +// "Release" operations ensure that no previous memory access can be reordered +// after the operation. "Barrier" operations have both "Acquire" and "Release" +// semantics. +Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr, + Atomic32 old_value, + Atomic32 new_value); +Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr, + Atomic32 old_value, + Atomic32 new_value); + +void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value); +void Acquire_Store(volatile Atomic32* ptr, Atomic32 value); +void Release_Store(volatile Atomic32* ptr, Atomic32 value); + +Atomic32 NoBarrier_Load(volatile const Atomic32* ptr); +Atomic32 Acquire_Load(volatile const Atomic32* ptr); +Atomic32 Release_Load(volatile const Atomic32* ptr); + +// 64-bit atomic operations (only available on 64-bit processors). +#ifdef ARCH_CPU_64_BITS +Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr, + Atomic64 old_value, + Atomic64 new_value); +Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr, Atomic64 new_value); +Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment); +Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment); + +Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr, + Atomic64 old_value, + Atomic64 new_value); +Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr, + Atomic64 old_value, + Atomic64 new_value); +void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value); +void Acquire_Store(volatile Atomic64* ptr, Atomic64 value); +void Release_Store(volatile Atomic64* ptr, Atomic64 value); +Atomic64 NoBarrier_Load(volatile const Atomic64* ptr); +Atomic64 Acquire_Load(volatile const Atomic64* ptr); +Atomic64 Release_Load(volatile const Atomic64* ptr); +#endif // ARCH_CPU_64_BITS + +} // namespace subtle +} // namespace base + +#if defined(OS_WIN) && defined(ARCH_CPU_X86_FAMILY) +// TODO(jfb): Try to use base/atomicops_internals_portable.h everywhere. +// https://crbug.com/559247. +# include "base/atomicops_internals_x86_msvc.h" +#else +# include "base/atomicops_internals_portable.h" +#endif + +// On some platforms we need additional declarations to make +// AtomicWord compatible with our other Atomic* types. +#if defined(OS_MACOSX) || defined(OS_OPENBSD) +#include "base/atomicops_internals_atomicword_compat.h" +#endif + +#endif // BASE_ATOMICOPS_H_ |