名前空間
変種
操作

std::atomic_flag_test_and_set, std::atomic_flag_test_and_set_explicit

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)
 
Defined in header <atomic>
bool atomic_flag_test_and_set( volatile std::atomic_flag* p );
(1) (C++11およびそれ以降)
bool atomic_flag_test_and_set( std::atomic_flag* p );
(2) (C++11およびそれ以降)
bool atomic_flag_test_and_set_explicit( volatile std::atomic_flag* p,
                                        std::memory_order order );
(3) (C++11およびそれ以降)
bool atomic_flag_test_and_set_explicit( std::atomic_flag* p,
                                        std::memory_order order );
(4) (C++11およびそれ以降)
アトミックに設定するstd::atomic_flagp)が指すtrueの状態を変更し、それが前に保持されている値を返します。.
Original:
Atomically changes the state of a std::atomic_flag pointed to by p to set (true) and returns the value it held before.
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目次

[編集] パラメータ

p -
アクセスするstd::atomic_flagへのポインタ
Original:
pointer to std::atomic_flag to access
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order -
この操作には、メモリーを同期順序
Original:
the memory synchronization order for this operation
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[編集] 値を返します

以前pが指すフラグが保持している値
Original:
The value previously held by the flag pointed to by p
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[編集] 例外

noexcept specification:  
noexcept
  (C++11およびそれ以降)

[編集] 可能な実装

First version
bool atomic_flag_test_and_set(volatile std::atomic_flag* p)
{
    return p->test_and_set();
}
Second version
bool atomic_flag_test_and_set(std::atomic_flag* p)
{
    return p->test_and_set();
}
Third version
bool atomic_flag_test_and_set_explicit(volatile std::atomic_flag* p, 
                                       std::memory_order order)
{
    return p->test_and_set(order);
}
Fourth version
bool atomic_flag_test_and_set_explicit(std::atomic_flag* p, 
                                       std::memory_order order) 
{
    return p->test_and_set(order);
}

[編集]

スピンロックmutexはatomic_flagを使用してユーザ空間で実装することができます
Original:
A spinlock mutex can be implemented in userspace using an atomic_flag
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#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(std::atomic_flag_test_and_set_explicit(&lock, std::memory_order_acquire))
             ; // spin until the lock is acquired
        std::cout << "Output from thread " << n << '\n';
        std::atomic_flag_clear_explicit(&lock, std::memory_order_release);
    }
}
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();
    }
}

Output:

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

[編集] も参照してください

ロックフリーブール原子型
Original:
the lock-free boolean atomic type
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(クラス) [edit]
アトミックfalseにフラグの値が設定されます
Original:
atomically sets the value of the flag to false
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(関数) [edit]
与えられたアトミック操作用のメモリ順序の制約を定義しています
Original:
defines memory ordering constraints for the given atomic operation
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(typedef) [edit]
C documentation for atomic_flag_test_and_set, atomic_flag_test_and_set_explicit