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// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
// Copyright (c) 2003, Google Inc.
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//
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// * Redistributions in binary form must reproduce the above
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// in the documentation and/or other materials provided with the
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// ---
//
// Author: Lei Zhang, Sasha Levitskiy
//
// This file is an internal atomic implementation, use base/atomicops.h instead.
//
// LinuxKernelCmpxchg is from Google Gears.
#ifndef BASE_ATOMICOPS_INTERNALS_ARM_GENERIC_H_
#define BASE_ATOMICOPS_INTERNALS_ARM_GENERIC_H_
#include <stdio.h>
#include "base/abort.h"
#include "base/basictypes.h"
typedef int32_t Atomic32;
namespace base {
namespace subtle {
typedef int64_t Atomic64;
// 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.
// pLinuxKernelCmpxchg has both acquire and release barrier sematincs.
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 Acquire_AtomicExchange(volatile Atomic32* ptr,
Atomic32 new_value) {
// pLinuxKernelCmpxchg already has acquire and release barrier semantics.
return NoBarrier_AtomicExchange(ptr, new_value);
}
inline Atomic32 Release_AtomicExchange(volatile Atomic32* ptr,
Atomic32 new_value) {
// pLinuxKernelCmpxchg already has acquire and release barrier semantics.
return NoBarrier_AtomicExchange(ptr, new_value);
}
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 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;
}
// 64-bit versions are not implemented yet.
inline void NotImplementedFatalError(const char *function_name) {
fprintf(stderr, "64-bit %s() not implemented on this platform\n",
function_name);
tcmalloc::Abort();
}
inline Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
Atomic64 old_value,
Atomic64 new_value) {
NotImplementedFatalError("NoBarrier_CompareAndSwap");
return 0;
}
inline Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr,
Atomic64 new_value) {
NotImplementedFatalError("NoBarrier_AtomicExchange");
return 0;
}
inline Atomic64 Acquire_AtomicExchange(volatile Atomic64* ptr,
Atomic64 new_value) {
// pLinuxKernelCmpxchg already has acquire and release barrier semantics.
return NoBarrier_AtomicExchange(ptr, new_value);
}
inline Atomic64 Release_AtomicExchange(volatile Atomic64* ptr,
Atomic64 new_value) {
// pLinuxKernelCmpxchg already has acquire and release barrier semantics.
return NoBarrier_AtomicExchange(ptr, new_value);
}
inline void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value) {
NotImplementedFatalError("NoBarrier_Store");
}
inline void Release_Store(volatile Atomic64* ptr, Atomic64 value) {
NotImplementedFatalError("Release_Store");
}
inline Atomic64 NoBarrier_Load(volatile const Atomic64* ptr) {
NotImplementedFatalError("NoBarrier_Load");
return 0;
}
inline Atomic64 Acquire_Load(volatile const Atomic64* ptr) {
NotImplementedFatalError("Atomic64 Acquire_Load");
return 0;
}
inline Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
Atomic64 old_value,
Atomic64 new_value) {
NotImplementedFatalError("Atomic64 Acquire_CompareAndSwap");
return 0;
}
inline Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
Atomic64 old_value,
Atomic64 new_value) {
NotImplementedFatalError("Atomic64 Release_CompareAndSwap");
return 0;
}
} // namespace base::subtle
} // namespace base
#endif // BASE_ATOMICOPS_INTERNALS_ARM_GENERIC_H_