On 27 January 2016 at 15:26, Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote: > On Wed, 2016-01-27 at 15:26 +0100, Michal Kazior wrote: >> >> @@ -1294,6 +1298,8 @@ struct sk_buff *ieee80211_tx_dequeue(struct >> ieee80211_hw *hw, >> if (!skb) >> goto out; >> >> + txqi->byte_cnt -= skb->len; >> + >> atomic_dec(&sdata->txqs_len[ac]); >> > This *looks* a bit worrying - you have an atomic dec for the # of > packets and a non-atomic one for the bytes. > > You probably thought about it and I guess it's fine, but can you > explain it? The atomic was used because it accesses per-vif counters. You can't use txqi->queue.lock for that. On the other hand byte_cnt is per txqi and it was very easy to make use of the txqi->queue.lock (which was already acquired in both drv_tx and tx_dequeue functions). Using atomic* for byte_cnt would be wasteful a bit. Michał -- 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
