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std::atomic_flag

提供: cppreference.com
< cpp‎ | atomic
 
 
アトミック操作ライブラリ
タイプ
Original:
Types
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atomic(C++11)
atomic_is_lock_free(C++11)
機能します
Original:
Functions
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atomic_store
atomic_store_explicit
(C++11)
(C++11)
atomic_load
atomic_load_explicit
(C++11)
(C++11)
atomic_exchange
atomic_exchange_explicit
(C++11)
(C++11)
atomic_compare_exchange_weak
atomic_compare_exchange_weak_explicit
atomic_compare_exchange_strong
atomic_compare_exchange_strong_explicit
(C++11)
(C++11)
(C++11)
(C++11)
atomic_fetch_add
atomic_fetch_add_explicit
(C++11)
(C++11)
atomic_fetch_sub
atomic_fetch_sub_explicit
(C++11)
(C++11)
atomic_fetch_and
atomic_fetch_and_explicit
(C++11)
(C++11)
atomic_fetch_or
atomic_fetch_or_explicit
(C++11)
(C++11)
atomic_fetch_xor
atomic_fetch_xor_explicit
(C++11)
(C++11)
アトミックのフラグ
Original:
Atomic flags
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atomic_flag(C++11)
atomic_flag_test_and_set
atomic_flag_test_and_set_explicit
(C++11)
(C++11)
atomic_flag_clear
atomic_flag_clear_explicit
(C++11)
(C++11)
初期化
Original:
Initialization
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atomic_init(C++11)
ATOMIC_VAR_INIT(C++11)
ATOMIC_FLAG_INIT(C++11)
メモリは発注
Original:
Memory ordering
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memory_order(C++11)
kill_dependency(C++11)
atomic_thread_fence(C++11)
atomic_signal_fence(C++11)
 
std::atomic_flag
メンバ関数
Original:
Member functions
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atomic_flag::atomic_flag
atomic_flag::operator=
atomic_flag::clear
atomic_flag::test_and_set
 
Defined in header <atomic>
class atomic_flag;
(C++11およびそれ以降)

std::atomic_flag はアトミックな boolean 型です。 std::atomic の特殊化とは異なり、ロックフリーであることが保証されています。 また、std::atomic<bool> とは異なり、std::atomic_flag はロード操作とストア操作を提供していません。

[編集] メンバ関数

atomic_flag を作成します
(パブリックメンバ関数)
代入演算子です
(パブリックメンバ関数)
アトミックにフラグをfalseに設定します
(パブリックメンバ関数) [edit]
アトミックにフラグをtrueに設定し、以前の値を返します
(パブリックメンバ関数) [edit]

[編集]

Spinlock mutex は atomic_flag を使用してユーザ空間で実装できます。

#include <thread>
#include <vector>
#include <iostream>
#include <atomic>
 
std::atomic_flag lock = ATOMIC_FLAG_INIT;
 
void f(int n)
{
    for(int cnt = 0; cnt < 100; ++cnt) {
        while(lock.test_and_set(std::memory_order_acquire))  // acquire lock
             ; // spin
        std::cout << "Output from thread " << n << '\n';
        lock.clear(std::memory_order_release);               // release lock
    }
}
int main()
{
    std::vector<std::thread> v;
    for (int n = 0; n < 10; ++n) {
        v.emplace_back(f, n);
    }
    for (auto& t : v) {
        t.join();
    }
}

出力:

Output from thread 2
Output from thread 6
Output from thread 7
...<exactly 1000 lines>...

[編集] 参考

アトミックにフラグをtrueに設定し、以前の値を返します
(関数) [edit]
アトミックにフラグの値をfalseに設定します
(関数) [edit]
std::atomic_flagfalse で初期化します
(マクロ定数) [edit]
C documentation for atomic_flag