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std::atomic_flag_test_and_set, std::atomic_flag_test_and_set_explicit

De cppreference.com
< cpp‎ | atomic

 
 
Atomique opérations de la bibliothèque
Types
Original:
Types
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atomic (C++11)
atomic_is_lock_free (C++11)
Fonctions
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)
Drapeaux atomiques
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)
Initialisation
Original:
Initialization
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atomic_init (C++11)
ATOMIC_VAR_INIT (C++11)
ATOMIC_FLAG_INIT (C++11)
Mémoire de la commande
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) (depuis C++11)
bool atomic_flag_test_and_set( std::atomic_flag* p );
(2) (depuis C++11)
bool atomic_flag_test_and_set_explicit( volatile std::atomic_flag* p,
                                        std::memory_order order );
(3) (depuis C++11)
bool atomic_flag_test_and_set_explicit( std::atomic_flag* p,
                                        std::memory_order order );
(4) (depuis C++11)
Change atomiquement l'état d'un std::atomic_flag pointé par p à régler (true) et renvoie la valeur qu'elle détenait avant .
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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Sommaire

[modifier] Paramètres

p -
pointeur vers std::atomic_flag d'accès
Original:
pointer to std::atomic_flag to access
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order -
la commande de synchronisation de mémoire pour cette opération
Original:
the memory synchronization order for this operation
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[modifier] Retourne la valeur

La valeur précédemment détenu par le drapeau pointé par p
Original:
The value previously held by the flag pointed to by p
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[modifier] Exceptions

noexcept specification:  
noexcept
   (depuis C++11)

[modifier] Mise en œuvre possible

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);
}

[modifier] Exemple

Un mutex spinlock peut être mis en œuvre dans l'espace utilisateur en utilisant un 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(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();
    }
}

Résultat :

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

[modifier] Voir aussi

(C++11)
la serrure sans type booléen atomique
Original:
the lock-free boolean atomic type
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(classe) [edit]
définit atomiquement la valeur de l'indicateur de false
Original:
atomically sets the value of the flag to false
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(fonction) [edit]
définit des contraintes de mémoire de commande pour l'opération donnée atomique
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