Incorrect Use of Memory Order for std::atomic

[Omer Faruk Atalay]

The acquire and release memory orders for std::atomic operations are used in the wrong places. They need to be switched to ensure correct synchronization. The code is located at atomic/synchronisation/sync_04.cpp.

Corrected code:

#include <atomic>
#include <syncstream>
#include <iostream>
#include <thread>

std::atomic<int> ready_flag{ false };
int svar = 0;

void consumer()
{
	while (!ready_flag.load(std::memory_order_acquire)) { // It was memory_order_release
		std::osyncstream{ std::cout }.put('.');
	}
	std::osyncstream{ std::cout } << '\n' << svar;
}


void producer()
{
	std::this_thread::sleep_for(std::chrono::milliseconds{ 50 });
	svar = 38764;
	ready_flag.store(true, std::memory_order_release); // It was memory_order_acquire
}

int main()
{
	std::thread th_c{ consumer };
	std::thread th_p{ producer };

	th_c.join();
	th_p.join();
}

[Necati Ergin]

Teşekkürler👍 25 Haz 2024 Sal, saat 14:40 tarihinde Omer Faruk Atalay < ***@***.***> şunu yazdı:

…

The acquire and release memory orders for std::atomic operations are used in the wrong places. They need to be switched to ensure correct synchronization. The code is located at atomic/synchronisation/sync_04.cpp. Corrected code: #include <atomic> #include <syncstream> #include <iostream> #include <thread> std::atomic<int> ready_flag{ false };int svar = 0; void consumer() { while (!ready_flag.load(std::memory_order_acquire)) { // It was memory_order_release std::osyncstream{ std::cout }.put('.'); } std::osyncstream{ std::cout } << '\n' << svar; } void producer() { std::this_thread::sleep_for(std::chrono::milliseconds{ 50 }); svar = 38764; ready_flag.store(true, std::memory_order_release); // It was memory_order_acquire } int main() { std::thread th_c{ consumer }; std::thread th_p{ producer }; th_c.join(); th_p.join(); } — Reply to this email directly, view it on GitHub <#1>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ALC5AJIPMACNJVOTTTKTGW3ZJFJLBAVCNFSM6AAAAABJ3VDN26VHI2DSMVQWIX3LMV43ASLTON2WKOZSGM3TENBWHEYDKNY> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>