/* Copyright (c) 2006, Google Inc.
* 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
*/
// For atomic operations on statistics counters, see atomic_stats_counter.h.
// For atomic operations on sequence numbers, see atomic_sequence_num.h.
// For atomic operations on reference counts, see atomic_refcount.h.
// Some fast atomic operations -- typically with machine-dependent
// implementations. This file may need editing as Google code is
// ported to different architectures.
// 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. Moreover, if you choose to use base::subtle::Atomic64 type,
// you MUST use one of the Load or Store routines to get correct behavior
// on 32-bit platforms.
//
// The intent is eventually to put all of these routines in namespace
// base::subtle
#ifndef THREAD_ATOMICOPS_H_
#define THREAD_ATOMICOPS_H_
#include <config.h>
#ifdef HAVE_STDINT_H
#include <stdint.h>
#endif
// ------------------------------------------------------------------------
// Include the platform specific implementations of the types
// and operations listed below. Implementations are to provide Atomic32
// and Atomic64 operations. If there is a mismatch between intptr_t and
// the Atomic32 or Atomic64 types for a platform, the platform-specific header
// should define the macro, AtomicWordCastType in a clause similar to the
// following:
// #if ...pointers are 64 bits...
// # define AtomicWordCastType base::subtle::Atomic64
// #else
// # define AtomicWordCastType Atomic32
// #endif
// TODO(csilvers): figure out ARCH_PIII/ARCH_K8 (perhaps via ./configure?)
// ------------------------------------------------------------------------
#include "base/arm_instruction_set_select.h"
// TODO(csilvers): match piii, not just __i386. Also, match k8
#if defined(__MACH__) && defined(__APPLE__)
#include "base/atomicops-internals-macosx.h"
#elif defined(__GNUC__) && defined(ARMV6)
#include "base/atomicops-internals-arm-v6plus.h"
#elif defined(ARMV3)
#include "base/atomicops-internals-arm-generic.h"
#elif defined(_WIN32)
#include "base/atomicops-internals-windows.h"
#elif defined(__GNUC__) && (defined(__i386) || defined(__x86_64__))
#include "base/atomicops-internals-x86.h"
#elif defined(__linux__) && defined(__PPC__)
#include "base/atomicops-internals-linuxppc.h"
#else
// Assume x86 for now. If you need to support a new architecture and
// don't know how to implement atomic ops, you can probably get away
// with using pthreads, since atomicops is only used by spinlock.h/cc
//#error You need to implement atomic operations for this architecture
#include "base/atomicops-internals-x86.h"
#endif
// Signed type that can hold a pointer and supports the atomic ops below, as
// well as atomic loads and stores. Instances must be naturally-aligned.
typedef intptr_t AtomicWord;
#ifdef AtomicWordCastType
// ------------------------------------------------------------------------
// This section is needed only when explicit type casting is required to
// cast AtomicWord to one of the basic atomic types (Atomic64 or Atomic32).
// It also serves to document the AtomicWord interface.
// ------------------------------------------------------------------------
namespace base {
namespace subtle {
// 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.
inline AtomicWord NoBarrier_CompareAndSwap(volatile AtomicWord* ptr,
AtomicWord old_value,
AtomicWord new_value) {
return NoBarrier_CompareAndSwap(
reinterpret_cast<volatile AtomicWordCastType*>(ptr),
old_value, new_value);
}
// Atomically store new_value into *ptr, returning the previous value held in
// *ptr. This routine implies no memory barriers.
inline AtomicWord NoBarrier_AtomicExchange(volatile AtomicWord* ptr,
AtomicWord new_value) {
return NoBarrier_AtomicExchange(
reinterpret_cast<volatile AtomicWordCastType*>(ptr), new_value);
}
// Atomically increment *ptr by "increment". Returns the new value of
// *ptr with the increment applied. This routine implies no memory
// barriers.
inline AtomicWord NoBarrier_AtomicIncrement(volatile AtomicWord* ptr,
AtomicWord increment) {
return NoBarrier_AtomicIncrement(
reinterpret_cast<volatile AtomicWordCastType*>(ptr), increment);
}
inline AtomicWord Barrier_AtomicIncrement(volatile AtomicWord* ptr,
AtomicWord increment) {
return Barrier_AtomicIncrement(
reinterpret_cast<volatile AtomicWordCastType*>(ptr), 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. A MemoryBarrier() has "Barrier" semantics, but does no memory
// access.
// ------------------------------------------------------------------------
inline AtomicWord Acquire_CompareAndSwap(volatile AtomicWord* ptr,
AtomicWord old_value,
AtomicWord new_value) {
return base::subtle::Acquire_CompareAndSwap(
reinterpret_cast<volatile AtomicWordCastType*>(ptr),
old_value, new_value);
}
inline AtomicWord Release_CompareAndSwap(volatile AtomicWord* ptr,
AtomicWord old_value,
AtomicWord new_value) {
return base::subtle::Release_CompareAndSwap(
reinterpret_cast<volatile AtomicWordCastType*>(ptr),
old_value, new_value);
}
inline void NoBarrier_Store(volatile AtomicWord *ptr, AtomicWord value) {
NoBarrier_Store(
reinterpret_cast<volatile AtomicWordCastType*>(ptr), value);
}
inline void Acquire_Store(volatile AtomicWord* ptr, AtomicWord value) {
return base::subtle::Acquire_Store(
reinterpret_cast<volatile AtomicWordCastType*>(ptr), value);
}
inline void Release_Store(volatile AtomicWord* ptr, AtomicWord value) {
return base::subtle::Release_Store(
reinterpret_cast<volatile AtomicWordCastType*>(ptr), value);
}
inline AtomicWord NoBarrier_Load(volatile const AtomicWord *ptr) {
return NoBarrier_Load(
reinterpret_cast<volatile const AtomicWordCastType*>(ptr));
}
inline AtomicWord Acquire_Load(volatile const AtomicWord* ptr) {
return base::subtle::Acquire_Load(
reinterpret_cast<volatile const AtomicWordCastType*>(ptr));
}
inline AtomicWord Release_Load(volatile const AtomicWord* ptr) {
return base::subtle::Release_Load(
reinterpret_cast<volatile const AtomicWordCastType*>(ptr));
}
} // namespace base::subtle
} // namespace base
#endif // AtomicWordCastType
// ------------------------------------------------------------------------
// Commented out type definitions and method declarations for documentation
// of the interface provided by this module.
// ------------------------------------------------------------------------
#if 0
// Signed 32-bit type that supports the atomic ops below, as well as atomic
// loads and stores. Instances must be naturally aligned. This type differs
// from AtomicWord in 64-bit binaries where AtomicWord is 64-bits.
typedef int32_t Atomic32;
// Corresponding operations on Atomic32
namespace base {
namespace subtle {
// Signed 64-bit type that supports the atomic ops below, as well as atomic
// loads and stores. Instances must be naturally aligned. This type differs
// from AtomicWord in 32-bit binaries where AtomicWord is 32-bits.
typedef int64_t Atomic64;
Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value);
Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, Atomic32 new_value);
Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, Atomic32 increment);
Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
Atomic32 increment);
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);
// Corresponding operations on Atomic64
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);
} // namespace base::subtle
} // namespace base
void MemoryBarrier();
#endif // 0
// ------------------------------------------------------------------------
// The following are to be deprecated when all uses have been changed to
// use the base::subtle namespace.
// ------------------------------------------------------------------------
#ifdef AtomicWordCastType
// AtomicWord versions to be deprecated
inline AtomicWord Acquire_CompareAndSwap(volatile AtomicWord* ptr,
AtomicWord old_value,
AtomicWord new_value) {
return base::subtle::Acquire_CompareAndSwap(ptr, old_value, new_value);
}
inline AtomicWord Release_CompareAndSwap(volatile AtomicWord* ptr,
AtomicWord old_value,
AtomicWord new_value) {
return base::subtle::Release_CompareAndSwap(ptr, old_value, new_value);
}
inline void Acquire_Store(volatile AtomicWord* ptr, AtomicWord value) {
return base::subtle::Acquire_Store(ptr, value);
}
inline void Release_Store(volatile AtomicWord* ptr, AtomicWord value) {
return base::subtle::Release_Store(ptr, value);
}
inline AtomicWord Acquire_Load(volatile const AtomicWord* ptr) {
return base::subtle::Acquire_Load(ptr);
}
inline AtomicWord Release_Load(volatile const AtomicWord* ptr) {
return base::subtle::Release_Load(ptr);
}
#endif // AtomicWordCastType
// 32-bit Acquire/Release operations to be deprecated.
inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
return base::subtle::Acquire_CompareAndSwap(ptr, old_value, new_value);
}
inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
return base::subtle::Release_CompareAndSwap(ptr, old_value, new_value);
}
inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
base::subtle::Acquire_Store(ptr, value);
}
inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
return base::subtle::Release_Store(ptr, value);
}
inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
return base::subtle::Acquire_Load(ptr);
}
inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
return base::subtle::Release_Load(ptr);
}
#ifdef BASE_HAS_ATOMIC64
// 64-bit Acquire/Release operations to be deprecated.
inline base::subtle::Atomic64 Acquire_CompareAndSwap(
volatile base::subtle::Atomic64* ptr,
base::subtle::Atomic64 old_value, base::subtle::Atomic64 new_value) {
return base::subtle::Acquire_CompareAndSwap(ptr, old_value, new_value);
}
inline base::subtle::Atomic64 Release_CompareAndSwap(
volatile base::subtle::Atomic64* ptr,
base::subtle::Atomic64 old_value, base::subtle::Atomic64 new_value) {
return base::subtle::Release_CompareAndSwap(ptr, old_value, new_value);
}
inline void Acquire_Store(
volatile base::subtle::Atomic64* ptr, base::subtle::Atomic64 value) {
base::subtle::Acquire_Store(ptr, value);
}
inline void Release_Store(
volatile base::subtle::Atomic64* ptr, base::subtle::Atomic64 value) {
return base::subtle::Release_Store(ptr, value);
}
inline base::subtle::Atomic64 Acquire_Load(
volatile const base::subtle::Atomic64* ptr) {
return base::subtle::Acquire_Load(ptr);
}
inline base::subtle::Atomic64 Release_Load(
volatile const base::subtle::Atomic64* ptr) {
return base::subtle::Release_Load(ptr);
}
#endif // BASE_HAS_ATOMIC64
#endif // THREAD_ATOMICOPS_H_