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std::atomic_flag_test_and_set, std::atomic_flag_test_and_set_explicit

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C++
 
Atomare Operationen Bibliothek
Types
Original:
Types
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atomic(C++11)
atomic_is_lock_free(C++11)
Funktionen
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)
Atomic Fahnen
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)
Initialisierung
Original:
Initialization
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atomic_init(C++11)
ATOMIC_VAR_INIT(C++11)
ATOMIC_FLAG_INIT(C++11)
Speicher Bestellung
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)
 
definiert in Header <atomic>
bool atomic_flag_test_and_set( volatile std::atomic_flag* p );
 (1) (seit C++11)
bool atomic_flag_test_and_set( std::atomic_flag* p );
 (2) (seit C++11)
bool atomic_flag_test_and_set_explicit( volatile std::atomic_flag* p,
                                        std::memory_order order );
 (3) (seit C++11)
bool atomic_flag_test_and_set_explicit( std::atomic_flag* p,
                                        std::memory_order order );
 (4) (seit C++11)
Atomar ändert den Zustand eines std::atomic_flag, auf die p auf (true) und gibt den Wert, bevor gehalten .
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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Inhaltsverzeichnis

[Bearbeiten] Parameter

p -
Zeiger auf std::atomic_flag zu erreichen
Original:
pointer to std::atomic_flag to access
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order -
der Speicher-Synchronisation, um für diesen Vorgang
Original:
the memory synchronization order for this operation
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[Bearbeiten] Rückgabewert

Die zuvor von der Flagge gehalten, auf die p
Original:
The value previously held by the flag pointed to by p
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[Bearbeiten] Ausnahmen

noexcept specification:  
noexcept
  (seit C++11)

[Bearbeiten] Mögliche Implementierung

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);
}

[Bearbeiten] Beispiel

Ein Spinlock Mutex kann im Userspace mit einem atomic_flag umgesetzt werden
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>...

[Bearbeiten] Siehe auch

(C++11)
Die Lock-freie boolean atomaren Typ
Original:
the lock-free boolean atomic type
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(Klasse) [edit]
(C++11)
(C++11)
atomar setzt den Wert der Flagge auf false
Original:
atomically sets the value of the flag to false
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(Funktion) [edit]
(C++11)
definiert Speicher Bestellung Einschränkungen für den angegebenen atomaren Operation
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
Von „https://de.cppreference.com/mwiki/index.php?title=cpp/atomic/atomic_flag_test_and_set&oldid=29288“