Re: [PATCH RFC v4 3/4] mac80211: Add airtime accounting and scheduling to TXQs

[Rajkumar Manoharan <rmanohar@codeaurora.org>]

On 2018-09-26 17:09, Rajkumar Manoharan wrote:
> On 2018-09-26 02:22, Toke Høiland-Jørgensen wrote:
>> Rajkumar Manoharan <rmanohar@codeaurora.org> writes:

> :( Yeah... I got confused with attached soft lockup in ARM platform.
> 
Toke,

Cause for the soft lockup exposed in multi client scenario is due to
mixed order of fq_lock and active_txqs_lock. In wake_tx_queue or 
push_pending
case, driver acquires active_txq_lock first by schedule_start and 
followed by
fq_lock in tx_dequeue. The same order should be maintained in sta 
cleanup.
Below change fixed the issue.

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 4814710a64f3..2029d600663b 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -114,9 +114,7 @@ static void __cleanup_single_sta(struct sta_info 
*sta)
                 for (i = 0; i < ARRAY_SIZE(sta->sta.txq); i++) {
                         struct txq_info *txqi = 
to_txq_info(sta->sta.txq[i]);

-                       spin_lock_bh(&fq->lock);
                         ieee80211_txq_purge(local, txqi);
-                       spin_unlock_bh(&fq->lock);
                 }
         }

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 884d9ce5ce4b..5d70f64a205c 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1467,8 +1467,10 @@ void ieee80211_txq_purge(struct ieee80211_local 
*local,
         struct fq *fq = &local->fq;
         struct fq_tin *tin = &txqi->tin;

+       spin_lock_bh(&fq->lock);
         fq_tin_reset(fq, tin, fq_skb_free_func);
         ieee80211_purge_tx_queue(&local->hw, &txqi->frags);
+       spin_unlock_bh(&fq->lock);
         spin_lock_bh(&local->active_txq_lock[txqi->txq.ac]);
         list_del_init(&txqi->schedule_order);
         spin_unlock_bh(&local->active_txq_lock[txqi->txq.ac]);

-Rajkumar