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zhangxing
2023-03-30 00:15:11 +08:00
committed by light-city
parent 1f86192576
commit 3c8a3f259b
641 changed files with 10349 additions and 9523 deletions
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43
design_pattern/singleton/cpulpuls11_singleton.cpp
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@@ -6,41 +6,40 @@
using namespace std;
#include <mutex>
#include <atomic>
#include <mutex>
//C++ 11版本之后的跨平台实现
// C++ 11版本之后的跨平台实现
class singleton {
private:
singleton() {}
singleton() {}
static mutex lock_;
static atomic<singleton *> p;
static mutex lock_;
static atomic<singleton *> p;
public:
singleton *instance();
singleton *instance();
};
mutex singleton::lock_;
atomic<singleton *> singleton::p;
/*
* std::atomic_thread_fence(std::memory_order_acquire);
* std::atomic_thread_fence(std::memory_order_release);
* 这两句话可以保证他们之间的语句不会发生乱序执行。
*/
* std::atomic_thread_fence(std::memory_order_acquire);
* std::atomic_thread_fence(std::memory_order_release);
* 这两句话可以保证他们之间的语句不会发生乱序执行。
*/
singleton *singleton::instance() {
singleton *tmp = p.load(memory_order_relaxed);
atomic_thread_fence(memory_order_acquire);
singleton *tmp = p.load(memory_order_relaxed);
atomic_thread_fence(memory_order_acquire);
if (tmp == nullptr) {
lock_guard<mutex> guard(lock_);
tmp = p.load(memory_order_relaxed);
if (tmp == nullptr) {
lock_guard<mutex> guard(lock_);
tmp = p.load(memory_order_relaxed);
if (tmp == nullptr) {
tmp = new singleton();
atomic_thread_fence(memory_order_release);
p.store(tmp, memory_order_relaxed);
}
tmp = new singleton();
atomic_thread_fence(memory_order_release);
p.store(tmp, memory_order_relaxed);
}
return p;
}
return p;
}