iwlwifi: mvm: don't transmit on unallocated queue

We can currently end up transmitting on an unallocated queue, if
the allocation fails. Stop doing that, by simply not transmitting.
We don't have any better strategy here, unfortunately, but the
previous commits make that much less likely.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200425130140.dcf1801f25ef.I6d71e13ea042765800f2ee41401b8eb282527c34@changeid

drivers/net/wireless/intel/iwlwifi/mvm/sta.c

@@ -1400,7 +1400,17 @@ void iwl_mvm_add_new_dqa_stream_wk(struct work_struct *wk)
 		if (tid == IEEE80211_NUM_TIDS)
 			tid = IWL_MAX_TID_COUNT;
 
-		iwl_mvm_sta_alloc_queue(mvm, txq->sta, txq->ac, tid);
+		/*
+		 * We can't really do much here, but if this fails we can't
+		 * transmit anyway - so just don't transmit the frame etc.
+		 * and let them back up ... we've tried our best to allocate
+		 * a queue in the function itself.
+		 */
+		if (iwl_mvm_sta_alloc_queue(mvm, txq->sta, txq->ac, tid)) {
+			list_del_init(&mvmtxq->list);
+			continue;
+		}
+
 		list_del_init(&mvmtxq->list);
 		local_bh_disable();
 		iwl_mvm_mac_itxq_xmit(mvm->hw, txq);