Does it makes sense to make atomic a BOOL flag in multithreading programming

I am quite new to multithreading programming and wonder if it is ok or to make a property like

@property BOOL shouldDoIt; //atomic

which will be used in a loop that is called in the background

- (void) loop{
    // ... do stuff ...
    if (self.shouldDoIt) {
        [self doIt];
        self.shouldDoIt = NO;
    }
    // ... do more stuff ...
}

and changed in a method called from the main thread

- (void) methodCalledFromMainThread{
    self.shouldDoIt = YES;
}

Do I have to make it atomic or it does not change anything? Я знаю, что atomic медленнее по сравнению с неатомарным, и моей программе нужно больше скорости, но если не использовать атомарный, то выполнение if (shouldDoIt) { может не сработать?