From 1375e3ba9d773f2dbac96ebddfdd0d160276ca40 Mon Sep 17 00:00:00 2001 From: Miquel Raynal Date: Tue, 14 Feb 2023 14:50:33 +0100 Subject: mac802154: Send beacons using the MLME Tx path Using ieee802154_subif_start_xmit() to bypass the net queue when sending beacons is broken because it does not acquire the HARD_TX_LOCK(), hence not preventing datagram buffers to be smashed by beacons upon contention situation. Using the mlme_tx helper is not the best fit either but at least it is not buggy and has little-to-no performance hit. More details are given in the comment explaining this choice in the code. Fixes: 3accf4762734 ("mac802154: Handle basic beaconing") Reported-by: Alexander Aring Signed-off-by: Miquel Raynal Link: https://lore.kernel.org/r/20230214135035.1202471-5-miquel.raynal@bootlin.com Signed-off-by: Stefan Schmidt --- net/mac802154/scan.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) (limited to 'net') diff --git a/net/mac802154/scan.c b/net/mac802154/scan.c index 8f98efec7753..fff41e59099e 100644 --- a/net/mac802154/scan.c +++ b/net/mac802154/scan.c @@ -326,7 +326,25 @@ static int mac802154_transmit_beacon(struct ieee802154_local *local, return ret; } - return ieee802154_subif_start_xmit(skb, sdata->dev); + /* Using the MLME transmission helper for sending beacons is a bit + * overkill because we do not really care about the final outcome. + * + * Even though, going through the whole net stack with a regular + * dev_queue_xmit() is not relevant either because we want beacons to be + * sent "now" rather than go through the whole net stack scheduling + * (qdisc & co). + * + * Finally, using ieee802154_subif_start_xmit() would only be an option + * if we had a generic transmit helper which would acquire the + * HARD_TX_LOCK() to prevent buffer handling conflicts with regular + * packets. + * + * So for now we keep it simple and send beacons with our MLME helper, + * even if it stops the ieee802154 queue entirely during these + * transmissions, wich anyway does not have a huge impact on the + * performances given the current design of the stack. + */ + return ieee802154_mlme_tx(local, sdata, skb); } void mac802154_beacon_worker(struct work_struct *work) -- cgit