Espaços nominais
Variantes
Acções

std::atomic_flag

Da cppreference.com
< cpp‎ | atomic

 
 
Biblioteca operações atômica
Tipos
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Types
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atomic(C++11)
atomic_is_lock_free(C++11)
Funções
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)
Bandeiras atômicas
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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)
Inicialização
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Initialization
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atomic_init(C++11)
ATOMIC_VAR_INIT(C++11)
ATOMIC_FLAG_INIT(C++11)
Memória de encomenda
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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
Funções de membro
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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;
(a partir do C++ 11)
std::atomic_flag é um tipo atômico boolean. Ao contrário de todas as especializações de std::atomic, é a garantia de ser livre de bloqueio. Ao contrário std::atomic<bool>, std::atomic_flag não fornece carga ou operações da loja.
Original:
std::atomic_flag is an atomic boolean type. Unlike all specializations of std::atomic, it is guaranteed to be lock-free. Unlike std::atomic<bool>, std::atomic_flag does not provide load or store operations.
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[editar] Funções de membro

constrói uma atomic_flag
Original:
constructs an atomic_flag
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(função pública membro)
o operador de atribuição
Original:
the assignment operator
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(função pública membro)
atomicamente define bandeira para false
Original:
atomically sets flag to false
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(função pública membro) [edit]
atomicamente define o sinalizador para true e obtém seu valor anterior
Original:
atomically sets the flag to true and obtains its previous value
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(função pública membro) [edit]

[editar] Exemplo

Um mutex spinlock pode ser implementado no userspace usando um atomic_flag
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(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();
    }
}

Output:

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

[editar] Veja também

atomicamente define o sinalizador para true e retorna seu valor anterior
Original:
atomically sets the flag to true and returns its previous value
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(função) [edit]
atomicamente define o valor da bandeira para false
Original:
atomically sets the value of the flag to false
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(função) [edit]
initializes an std::atomic_flag to false
(macro constante) [edit]
C documentation for atomic_flag