linux-kernel - [PATCH 4.9 005/171] mac80211: fix pending queue hang due to TX

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Message-Id: <20181108215127.583789452@linuxfoundation.org>
Date:   Thu,  8 Nov 2018 13:49:35 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Bob Copeland <bobcopeland@...com>,
        Toke Høiland-Jørgensen <toke@...e.dk>,
        Johannes Berg <johannes.berg@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 005/171] mac80211: fix pending queue hang due to TX_DROP

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 6eae4a6c2be387fec41b0d2782c4fffb57159498 ]

In our environment running lots of mesh nodes, we are seeing the
pending queue hang periodically, with the debugfs queues file showing
lines such as:

    00: 0x00000000/348

i.e. there are a large number of frames but no stop reason set.

One way this could happen is if queue processing from the pending
tasklet exited early without processing all frames, and without having
some future event (incoming frame, stop reason flag, ...) to reschedule
it.

Exactly this can occur today if ieee80211_tx() returns false due to
packet drops or power-save buffering in the tx handlers.  In the
past, this function would return true in such cases, and the change
to false doesn't seem to be intentional.  Fix this case by reverting
to the previous behavior.

Fixes: bb42f2d13ffc ("mac80211: Move reorder-sensitive TX handlers to after TXQ dequeue")
Signed-off-by: Bob Copeland <bobcopeland@...com>
Acked-by: Toke Høiland-Jørgensen <toke@...e.dk>
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/mac80211/tx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 84582998f65f..58fba4e569e6 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1833,7 +1833,7 @@ static bool ieee80211_tx(struct ieee80211_sub_if_data *sdata,
 			sdata->vif.hw_queue[skb_get_queue_mapping(skb)];
 
 	if (invoke_tx_handlers_early(&tx))
-		return false;
+		return true;
 
 	if (ieee80211_queue_skb(local, sdata, tx.sta, tx.skb))
 		return true;
-- 
2.17.1