| // Protocol Buffers - Google's data interchange format |
| // Copyright 2012 Google Inc. All rights reserved. |
| // https://developers.google.com/protocol-buffers/ |
| // |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
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| // 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. |
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| // 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 |
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| |
| // This file is an internal atomic implementation, use atomicops.h instead. |
| // |
| // LinuxKernelCmpxchg and Barrier_AtomicIncrement are from Google Gears. |
| |
| #ifndef GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_ARM_GCC_H_ |
| #define GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_ARM_GCC_H_ |
| |
| namespace google { |
| namespace protobuf { |
| namespace internal { |
| |
| // 0xffff0fc0 is the hard coded address of a function provided by |
| // the kernel which implements an atomic compare-exchange. On older |
| // ARM architecture revisions (pre-v6) this may be implemented using |
| // a syscall. This address is stable, and in active use (hard coded) |
| // by at least glibc-2.7 and the Android C library. |
| typedef Atomic32 (*LinuxKernelCmpxchgFunc)(Atomic32 old_value, |
| Atomic32 new_value, |
| volatile Atomic32* ptr); |
| LinuxKernelCmpxchgFunc pLinuxKernelCmpxchg __attribute__((weak)) = |
| (LinuxKernelCmpxchgFunc) 0xffff0fc0; |
| |
| typedef void (*LinuxKernelMemoryBarrierFunc)(void); |
| LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier __attribute__((weak)) = |
| (LinuxKernelMemoryBarrierFunc) 0xffff0fa0; |
| |
| |
| inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr, |
| Atomic32 old_value, |
| Atomic32 new_value) { |
| Atomic32 prev_value = *ptr; |
| do { |
| if (!pLinuxKernelCmpxchg(old_value, new_value, |
| const_cast<Atomic32*>(ptr))) { |
| return old_value; |
| } |
| prev_value = *ptr; |
| } while (prev_value == old_value); |
| return prev_value; |
| } |
| |
| inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, |
| Atomic32 new_value) { |
| Atomic32 old_value; |
| do { |
| old_value = *ptr; |
| } while (pLinuxKernelCmpxchg(old_value, new_value, |
| const_cast<Atomic32*>(ptr))); |
| return old_value; |
| } |
| |
| inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, |
| Atomic32 increment) { |
| return Barrier_AtomicIncrement(ptr, increment); |
| } |
| |
| inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr, |
| Atomic32 increment) { |
| for (;;) { |
| // Atomic exchange the old value with an incremented one. |
| Atomic32 old_value = *ptr; |
| Atomic32 new_value = old_value + increment; |
| if (pLinuxKernelCmpxchg(old_value, new_value, |
| const_cast<Atomic32*>(ptr)) == 0) { |
| // The exchange took place as expected. |
| return new_value; |
| } |
| // Otherwise, *ptr changed mid-loop and we need to retry. |
| } |
| } |
| |
| inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr, |
| Atomic32 old_value, |
| Atomic32 new_value) { |
| return NoBarrier_CompareAndSwap(ptr, old_value, new_value); |
| } |
| |
| inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr, |
| Atomic32 old_value, |
| Atomic32 new_value) { |
| return NoBarrier_CompareAndSwap(ptr, old_value, new_value); |
| } |
| |
| inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) { |
| *ptr = value; |
| } |
| |
| inline void MemoryBarrier() { |
| pLinuxKernelMemoryBarrier(); |
| } |
| |
| inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) { |
| *ptr = value; |
| MemoryBarrier(); |
| } |
| |
| inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) { |
| MemoryBarrier(); |
| *ptr = value; |
| } |
| |
| inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) { |
| return *ptr; |
| } |
| |
| inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) { |
| Atomic32 value = *ptr; |
| MemoryBarrier(); |
| return value; |
| } |
| |
| inline Atomic32 Release_Load(volatile const Atomic32* ptr) { |
| MemoryBarrier(); |
| return *ptr; |
| } |
| |
| } // namespace internal |
| } // namespace protobuf |
| } // namespace google |
| |
| #endif // GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_ARM_GCC_H_ |