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Diffstat (limited to 'src/leveldb/port/atomic_pointer.h')
-rw-r--r-- | src/leveldb/port/atomic_pointer.h | 245 |
1 files changed, 0 insertions, 245 deletions
diff --git a/src/leveldb/port/atomic_pointer.h b/src/leveldb/port/atomic_pointer.h deleted file mode 100644 index d79a02230d..0000000000 --- a/src/leveldb/port/atomic_pointer.h +++ /dev/null @@ -1,245 +0,0 @@ -// Copyright (c) 2011 The LevelDB Authors. All rights reserved. -// Use of this source code is governed by a BSD-style license that can be -// found in the LICENSE file. See the AUTHORS file for names of contributors. - -// AtomicPointer provides storage for a lock-free pointer. -// Platform-dependent implementation of AtomicPointer: -// - If the platform provides a cheap barrier, we use it with raw pointers -// - If <atomic> is present (on newer versions of gcc, it is), we use -// a <atomic>-based AtomicPointer. However we prefer the memory -// barrier based version, because at least on a gcc 4.4 32-bit build -// on linux, we have encountered a buggy <atomic> implementation. -// Also, some <atomic> implementations are much slower than a memory-barrier -// based implementation (~16ns for <atomic> based acquire-load vs. ~1ns for -// a barrier based acquire-load). -// This code is based on atomicops-internals-* in Google's perftools: -// http://code.google.com/p/google-perftools/source/browse/#svn%2Ftrunk%2Fsrc%2Fbase - -#ifndef PORT_ATOMIC_POINTER_H_ -#define PORT_ATOMIC_POINTER_H_ - -#include <stdint.h> -#ifdef LEVELDB_ATOMIC_PRESENT -#include <atomic> -#endif -#ifdef OS_WIN -#include <windows.h> -#endif -#ifdef OS_MACOSX -#include <libkern/OSAtomic.h> -#endif - -#if defined(_M_X64) || defined(__x86_64__) -#define ARCH_CPU_X86_FAMILY 1 -#elif defined(_M_IX86) || defined(__i386__) || defined(__i386) -#define ARCH_CPU_X86_FAMILY 1 -#elif defined(__ARMEL__) -#define ARCH_CPU_ARM_FAMILY 1 -#elif defined(__aarch64__) -#define ARCH_CPU_ARM64_FAMILY 1 -#elif defined(__ppc__) || defined(__powerpc__) || defined(__powerpc64__) -#define ARCH_CPU_PPC_FAMILY 1 -#elif defined(__mips__) -#define ARCH_CPU_MIPS_FAMILY 1 -#endif - -namespace leveldb { -namespace port { - -// AtomicPointer based on <cstdatomic> if available -#if defined(LEVELDB_ATOMIC_PRESENT) -class AtomicPointer { - private: - std::atomic<void*> rep_; - public: - AtomicPointer() { } - explicit AtomicPointer(void* v) : rep_(v) { } - inline void* Acquire_Load() const { - return rep_.load(std::memory_order_acquire); - } - inline void Release_Store(void* v) { - rep_.store(v, std::memory_order_release); - } - inline void* NoBarrier_Load() const { - return rep_.load(std::memory_order_relaxed); - } - inline void NoBarrier_Store(void* v) { - rep_.store(v, std::memory_order_relaxed); - } -}; - -#else - -// Define MemoryBarrier() if available -// Windows on x86 -#if defined(OS_WIN) && defined(COMPILER_MSVC) && defined(ARCH_CPU_X86_FAMILY) -// windows.h already provides a MemoryBarrier(void) macro -// http://msdn.microsoft.com/en-us/library/ms684208(v=vs.85).aspx -#define LEVELDB_HAVE_MEMORY_BARRIER - -// Mac OS -#elif defined(OS_MACOSX) -inline void MemoryBarrier() { - OSMemoryBarrier(); -} -#define LEVELDB_HAVE_MEMORY_BARRIER - -// Gcc on x86 -#elif defined(ARCH_CPU_X86_FAMILY) && defined(__GNUC__) -inline void MemoryBarrier() { - // See http://gcc.gnu.org/ml/gcc/2003-04/msg01180.html for a discussion on - // this idiom. Also see http://en.wikipedia.org/wiki/Memory_ordering. - __asm__ __volatile__("" : : : "memory"); -} -#define LEVELDB_HAVE_MEMORY_BARRIER - -// Sun Studio -#elif defined(ARCH_CPU_X86_FAMILY) && defined(__SUNPRO_CC) -inline void MemoryBarrier() { - // See http://gcc.gnu.org/ml/gcc/2003-04/msg01180.html for a discussion on - // this idiom. Also see http://en.wikipedia.org/wiki/Memory_ordering. - asm volatile("" : : : "memory"); -} -#define LEVELDB_HAVE_MEMORY_BARRIER - -// ARM Linux -#elif defined(ARCH_CPU_ARM_FAMILY) && defined(__linux__) -typedef void (*LinuxKernelMemoryBarrierFunc)(void); -// The Linux ARM kernel provides a highly optimized device-specific memory -// barrier function at a fixed memory address that is mapped in every -// user-level process. -// -// This beats using CPU-specific instructions which are, on single-core -// devices, un-necessary and very costly (e.g. ARMv7-A "dmb" takes more -// than 180ns on a Cortex-A8 like the one on a Nexus One). Benchmarking -// shows that the extra function call cost is completely negligible on -// multi-core devices. -// -inline void MemoryBarrier() { - (*(LinuxKernelMemoryBarrierFunc)0xffff0fa0)(); -} -#define LEVELDB_HAVE_MEMORY_BARRIER - -// ARM64 -#elif defined(ARCH_CPU_ARM64_FAMILY) -inline void MemoryBarrier() { - asm volatile("dmb sy" : : : "memory"); -} -#define LEVELDB_HAVE_MEMORY_BARRIER - -// PPC -#elif defined(ARCH_CPU_PPC_FAMILY) && defined(__GNUC__) -inline void MemoryBarrier() { - // TODO for some powerpc expert: is there a cheaper suitable variant? - // Perhaps by having separate barriers for acquire and release ops. - asm volatile("sync" : : : "memory"); -} -#define LEVELDB_HAVE_MEMORY_BARRIER - -// MIPS -#elif defined(ARCH_CPU_MIPS_FAMILY) && defined(__GNUC__) -inline void MemoryBarrier() { - __asm__ __volatile__("sync" : : : "memory"); -} -#define LEVELDB_HAVE_MEMORY_BARRIER - -#endif - -// AtomicPointer built using platform-specific MemoryBarrier() -#if defined(LEVELDB_HAVE_MEMORY_BARRIER) -class AtomicPointer { - private: - void* rep_; - public: - AtomicPointer() { } - explicit AtomicPointer(void* p) : rep_(p) {} - inline void* NoBarrier_Load() const { return rep_; } - inline void NoBarrier_Store(void* v) { rep_ = v; } - inline void* Acquire_Load() const { - void* result = rep_; - MemoryBarrier(); - return result; - } - inline void Release_Store(void* v) { - MemoryBarrier(); - rep_ = v; - } -}; - -// Atomic pointer based on sparc memory barriers -#elif defined(__sparcv9) && defined(__GNUC__) -class AtomicPointer { - private: - void* rep_; - public: - AtomicPointer() { } - explicit AtomicPointer(void* v) : rep_(v) { } - inline void* Acquire_Load() const { - void* val; - __asm__ __volatile__ ( - "ldx [%[rep_]], %[val] \n\t" - "membar #LoadLoad|#LoadStore \n\t" - : [val] "=r" (val) - : [rep_] "r" (&rep_) - : "memory"); - return val; - } - inline void Release_Store(void* v) { - __asm__ __volatile__ ( - "membar #LoadStore|#StoreStore \n\t" - "stx %[v], [%[rep_]] \n\t" - : - : [rep_] "r" (&rep_), [v] "r" (v) - : "memory"); - } - inline void* NoBarrier_Load() const { return rep_; } - inline void NoBarrier_Store(void* v) { rep_ = v; } -}; - -// Atomic pointer based on ia64 acq/rel -#elif defined(__ia64) && defined(__GNUC__) -class AtomicPointer { - private: - void* rep_; - public: - AtomicPointer() { } - explicit AtomicPointer(void* v) : rep_(v) { } - inline void* Acquire_Load() const { - void* val ; - __asm__ __volatile__ ( - "ld8.acq %[val] = [%[rep_]] \n\t" - : [val] "=r" (val) - : [rep_] "r" (&rep_) - : "memory" - ); - return val; - } - inline void Release_Store(void* v) { - __asm__ __volatile__ ( - "st8.rel [%[rep_]] = %[v] \n\t" - : - : [rep_] "r" (&rep_), [v] "r" (v) - : "memory" - ); - } - inline void* NoBarrier_Load() const { return rep_; } - inline void NoBarrier_Store(void* v) { rep_ = v; } -}; - -// We have neither MemoryBarrier(), nor <atomic> -#else -#error Please implement AtomicPointer for this platform. - -#endif -#endif - -#undef LEVELDB_HAVE_MEMORY_BARRIER -#undef ARCH_CPU_X86_FAMILY -#undef ARCH_CPU_ARM_FAMILY -#undef ARCH_CPU_ARM64_FAMILY -#undef ARCH_CPU_PPC_FAMILY - -} // namespace port -} // namespace leveldb - -#endif // PORT_ATOMIC_POINTER_H_ |