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// Copyright (C) 2014 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "emugl/common/lazy_instance.h"
#ifdef _WIN32
# define WIN32_LEAN_AND_MEAN 1
# include <windows.h>
#else
# include <sched.h>
#endif
namespace emugl {
namespace internal {
typedef LazyInstanceState::AtomicType AtomicType;
#if defined(__GNUC__)
static inline void compilerBarrier() {
__asm__ __volatile__ ("" : : : "memory");
}
#else
#error "Your compiler is not supported"
#endif
#if defined(__i386__) || defined(__x86_64__)
# define acquireBarrier() compilerBarrier()
# define releaseBarrier() compilerBarrier()
#else
# error "Your CPU is not supported"
#endif
static inline AtomicType loadAcquire(AtomicType volatile* ptr) {
AtomicType ret = *ptr;
acquireBarrier();
return ret;
}
static inline void storeRelease(AtomicType volatile* ptr, AtomicType value) {
releaseBarrier();
*ptr = value;
}
static int atomicCompareAndSwap(AtomicType volatile* ptr,
int expected,
int value) {
#ifdef _WIN32
return InterlockedCompareExchange(ptr, value, expected);
#elif defined(__GNUC__)
return __sync_val_compare_and_swap(ptr, expected, value);
#else
#error "Your compiler is not supported"
#endif
}
static void yieldThread() {
#ifdef _WIN32
::Sleep(0);
#else
sched_yield();
#endif
}
bool LazyInstanceState::inInitState() {
return loadAcquire(&mState) == STATE_INIT;
}
bool LazyInstanceState::needConstruction() {
AtomicType state = loadAcquire(&mState);
if (mState == STATE_DONE)
return false;
state = atomicCompareAndSwap(&mState, STATE_INIT, STATE_CONSTRUCTING);
if (state == STATE_INIT)
return true;
do {
yieldThread();
state = loadAcquire(&mState);
} while (state != STATE_DONE);
return false;
}
void LazyInstanceState::doneConstructing() {
storeRelease(&mState, STATE_DONE);
}
} // namespace internal
} // namespace emugl
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