iwlwifi: mvm: avoid possible deadlock in TX path

iwl_mvm_tx_mpdu() may run from iwl_mvm_add_new_dqa_stream_wk(), where
soft-IRQs aren't disabled. In this case, it may hold the station lock
and be interrupted by a soft-IRQ that also wants to acquire said lock,
leading to a deadlock.

Fix it by disabling soft-IRQs in iwl_mvm_add_new_dqa_stream_wk().

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

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

@@ -1399,7 +1399,9 @@ void iwl_mvm_add_new_dqa_stream_wk(struct work_struct *wk)
 
 		iwl_mvm_sta_alloc_queue(mvm, txq->sta, txq->ac, tid);
 		list_del_init(&mvmtxq->list);
+		local_bh_disable();
 		iwl_mvm_mac_itxq_xmit(mvm->hw, txq);
+		local_bh_enable();
 	}
 
 	mutex_unlock(&mvm->mutex);