From: Johannes Berg johannes.berg@intel.com
commit 1153a74768a9212daadbb50767aa400bc6a0c9b0 upstream.
Normally, TXQs have
txq->tid = tid; txq->ac = ieee80211_ac_from_tid(tid);
However, the special management TXQ actually has
txq->tid = IEEE80211_NUM_TIDS; // 16 txq->ac = IEEE80211_AC_VO;
This makes sense, but ieee80211_ac_from_tid(16) is the same as ieee80211_ac_from_tid(0) which is just IEEE80211_AC_BE.
Now, normally this is fine. However, if the netdev queues were stopped, then the code in ieee80211_tx_dequeue() will propagate the stop from the interface (vif->txqs_stopped[]) if the AC 2 (ieee80211_ac_from_tid(txq->tid)) is marked as stopped. On wake, however, __ieee80211_wake_txqs() will wake the TXQ if AC 0 (txq->ac) is woken up.
If a driver stops all queues with ieee80211_stop_tx_queues() and then wakes them again with ieee80211_wake_tx_queues(), the ieee80211_wake_txqs() tasklet will run to resync queue and TXQ state. If all queues were woken, then what'll happen is that _ieee80211_wake_txqs() will run in order of HW queues 0-3, typically (and certainly for iwlwifi) corresponding to ACs 0-3, so it'll call __ieee80211_wake_txqs() for each AC in order 0-3.
When __ieee80211_wake_txqs() is called for AC 0 (VO) that'll wake up the management TXQ (remember its tid is 16), and the driver's wake_tx_queue() will be called. That tries to get a frame, which will immediately *stop* the TXQ again, because now we check against AC 2, and AC 2 hasn't yet been marked as woken up again in sdata->vif.txqs_stopped[] since we're only in the __ieee80211_wake_txqs() call for AC 0.
Thus, the management TXQ will never be started again.
Fix this by checking txq->ac directly instead of calculating the AC as ieee80211_ac_from_tid(txq->tid).
Fixes: adf8ed01e4fd ("mac80211: add an optional TXQ for other PS-buffered frames") Acked-by: Toke Høiland-Jørgensen toke@redhat.com Link: https://lore.kernel.org/r/20210323210500.bf4d50afea4a.I136ffde910486301f8818... Signed-off-by: Johannes Berg johannes.berg@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mac80211/tx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -3605,7 +3605,7 @@ begin: test_bit(IEEE80211_TXQ_STOP_NETIF_TX, &txqi->flags)) goto out;
- if (vif->txqs_stopped[ieee80211_ac_from_tid(txq->tid)]) { + if (vif->txqs_stopped[txq->ac]) { set_bit(IEEE80211_TXQ_STOP_NETIF_TX, &txqi->flags); goto out; }