friend void transfer(account& from,account& to,
float amount)
{
std::lock_guard<std::mutex> lock_from(from.m);
std::lock_guard<std::mutex> lock_to(to.m);
from.balance -= amount;
to.balance += amount;
}
void transfer2(account& from,account& to,
float amount)
{
std::lock(from.m,to.m);
std::lock_guard<std::mutex> lock_from(from.m,std::adopt_lock);
std::lock_guard<std::mutex> lock_to(to.m,std::adopt_lock);
from.balance -= amount;
to.balance += amount;
}
void transfer(int client_id, Account& from, Account& to, int amount) {
std::unique_lock<std::mutex> lock_from(from.getLock());
if (from.withdraw(amount)) {
std::printf("%d: withdraw %d OK\n", client_id, amount);
fflush(stdout); // to see withdraw messages
std::unique_lock<std::mutex> lock_to(to.getLock());
to.deposit(amount);
lock_to.unlock();
lock_from.unlock();
std::printf("%d: deposit %d OK\n", client_id, amount);
} else {
lock_from.unlock();
std::printf("%d: withdraw %d ERROR\n", client_id, amount);
}
}
void client(int client_id, Account& from, Account& to, int amount) {
bool success = false;
std::unique_lock<std::mutex> lock_from(from.getDeferLock());
std::unique_lock<std::mutex> lock_to(to.getDeferLock());
while(true) {
if (lock_from.try_lock()) {
if (lock_to.try_lock()) {
transfer(client_id, from, to, amount);
lock_to.unlock();
success = true;
}
lock_from.unlock();
}
if (success) break;
std::cout << "RETRY\n";
std::this_thread::sleep_for(std::chrono::milliseconds(rand()%100));
}
}