Yibo Zhao <yiboz@xxxxxxxxxxxxxx> writes:
> Global airtime weight sum is updated only when txq is added/removed
> from rbtree. If upper layer configures sta weight during high load,
> airtime weight sum will not be updated since txq is most likely on the
> tree. It could a little late for upper layer to reconfigure sta weight
> when txq is already in the rbtree. And thus, incorrect airtime weight sum
> will lead to incorrect global virtual time calculation as well as global
> airtime weight sum overflow of airtime weight sum during txq removed.
>
> Hence, need to update airtime weight sum upon receiving event for
> configuring sta weight once sta's txq is on the rbtree.
>
> Besides, if airtime weight sum of ACs and sta weight is synced under the
> same per AC lock protection, there can be a very short window causing
> incorrct airtime weight sum calculation as below:
>
> active_txq_lock_VO .
> VO weight sum is syncd .
> sta airtime weight sum is synced .
> active_txq_unlock_VO .
> . .
> active_txq_lock_VI .
> VI weight sum is syncd .
> sta airtime weight sum active_txq_lock_BE
> active_txq_unlock_VI Remove txq and thus sum
> . is calculated with synced
> . sta airtime weight
> . active_txq_unlock_BE
>
> So introduce a per ac synced station airtime weight synced with per
> AC synced weight sum together. And the per-AC station airtime weight
> is used to calculate weight sum.
>
> Signed-off-by: Yibo Zhao <yiboz@xxxxxxxxxxxxxx>
> ---
> net/mac80211/cfg.c | 27 +++++++++++++++++++++++++--
> net/mac80211/sta_info.c | 6 ++++--
> net/mac80211/sta_info.h | 3 +++
> net/mac80211/tx.c | 4 ++--
> 4 files changed, 34 insertions(+), 6 deletions(-)
>
> diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
> index d65aa01..4b420bb 100644
> --- a/net/mac80211/cfg.c
> +++ b/net/mac80211/cfg.c
> @@ -1284,7 +1284,8 @@ static int sta_apply_parameters(struct ieee80211_local *local,
> int ret = 0;
> struct ieee80211_supported_band *sband;
> struct ieee80211_sub_if_data *sdata = sta->sdata;
> - u32 mask, set;
> + u32 mask, set, tid, ac;
> + struct txq_info *txqi;
>
> sband = ieee80211_get_sband(sdata);
> if (!sband)
> @@ -1452,8 +1453,30 @@ static int sta_apply_parameters(struct ieee80211_local *local,
> if (ieee80211_vif_is_mesh(&sdata->vif))
> sta_apply_mesh_params(local, sta, params);
>
> - if (params->airtime_weight)
> + if (params->airtime_weight &&
> + params->airtime_weight != sta->airtime_weight) {
> + for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
> + spin_lock_bh(&local->active_txq_lock[ac]);
> + for (tid = 0; tid < IEEE80211_NUM_TIDS + 1; tid++) {
> + if (!sta->sta.txq[tid] ||
> + ac != ieee80211_ac_from_tid(tid))
> + continue;
> +
> + sta->airtime_weight_synced[ac] =
> + params->airtime_weight;
> +
> + txqi = to_txq_info(sta->sta.txq[tid]);
> + if (RB_EMPTY_NODE(&txqi->schedule_order))
> + continue;
> +
> + local->airtime_weight_sum[ac] = local->airtime_weight_sum[ac] +
> + params->airtime_weight -
> + sta->airtime_weight;
> + }
> + spin_unlock_bh(&local->active_txq_lock[ac]);
> + }
> sta->airtime_weight = params->airtime_weight;
With this, airtime_weight is basically only used to return to and from
userspace, right? I.e., after the above loop has run, it will match the
contents of airtime_weight_synced; so why not just turn airtime_weight
into a per-ac array? You could just use airtime_weight[0] as the value
to return to userspace...
-Toke
