Should a Return statement be outside of critical section?

Question

I am taking an operating systems course. I would like to ask about Locks and critical section. Consider the following C function that can be called by multiple threads. I use a lock whenever the shared resource balance is used.

int withdraw(account, amount) 
{
     acquire(lock);
     balance = get_balance(account);
     balance = balance - amount;
     put_balance(account, balance);
     release(lock);
     return balance;
}

My question is should I do it like that or should I release the lock after the return statement? What are the consequences of either way and which of them is a better practice?

I saw another similar Question but it I couldn't understand from it what is the proper thing to do in my example case.

Answer 1

The question you linked to is about C# code, not C. In C#, the lock is automatically released when you return from within a lock block. In C, there is no lock statement. You always need to release it yourself. If you return from within the critical section, the lock will not be released, because none of the statements that come after a return statement will be executed.