On Mon, 2007-12-10 at 08:21 +0100, Stefano Brivio wrote: > On Mon, 10 Dec 2007 07:28:01 +0100 > Mattias Nissler <mattias.nissler@xxxxxx> wrote: > > > > - /* If no frames were transmitted, we assume the old sample is > > > - * still a good measurement and copy it. */ > > > - if (spinfo->tx_num_xmit == 0) > > > - pf = spinfo->last_pf; > > > > Please don't remove this check. We can never know when anybody starts > > calling rate_control_pid_sample() without packets transmitted. Then it's > > good to have it, else we divide by zero in the next line. > > But, as you said, rate_control_pid_sample() only gets called by > rate_control_pid_tx_status(). There, spinfo->tx_num_xmit always get > increased. The only other spot where spinfo->tx_num_xmit gets changed is in > rate_control_pid_sample(), where we set it to 0 after that that division > gets done, and we obviously change its value after having been called by > rate_control_pid_tx_status(). So, it always get increased before the > division, and it's never set to a negative value. Therefore, I assume that > it will never be zero in the division. Am I wrong? You're totally right. But IMHO it's nicer to be a little defensive here. You never know what happens to your code in the future. Just imagine somebody coming up with: Hey, let's use a timer-based approach for sampling. Ok, that's easy to do, just call sample() every time the timer expires. And whoops, there's the division by zero when no packets are transmitted... Mattias - To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
