4
在這個例子中:採集/釋放內存訂貨
#include <thread>
#include <atomic>
#include <cassert>
#include <vector>
std::vector<int> data;
std::atomic<int> flag = ATOMIC_VAR_INIT(0);
void thread_1()
{
data.push_back(42);
flag.store(1, std::memory_order_release);
}
void thread_2()
{
int expected=1;
while (!flag.compare_exchange_strong(expected, 2, std::memory_order_acq_rel)) {
expected = 1;
}
}
void thread_3()
{
while (flag.load(std::memory_order_acquire) < 2)
;
assert(data.at(0) == 42); // will never fire
}
int main()
{
std::thread a(thread_1);
std::thread b(thread_2);
std::thread c(thread_3);
a.join(); b.join(); c.join();
}
1 - 如果我用的std :: memory_order_acquire替換的std :: memory_order_acq_rel在thread_2,我仍然可以保證在thread_3斷言絕不會火?
2 - 可以std :: memory_order_release使用std :: memory_order_acquire與2個線程同步(如果2個線程正在通過獲取語義觀察相同的標誌)?
僅供參考,'ATOMIC_VAR_INIT(foo)'提供C兼容性,'std :: atomic flag {foo};'具有完全相同的效果。 –
Casey