linux-kernel - [PATCH AUTOSEL 4.14 07/61] mac80211: fix pending queue hang due to TX

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Message-Id: <20181016041403.135678-7-sashal@kernel.org>
Date:   Tue, 16 Oct 2018 00:13:09 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Bob Copeland <me@...copeland.com>,
        Bob Copeland <bobcopeland@...com>,
        Johannes Berg <johannes.berg@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.14 07/61] mac80211: fix pending queue hang due to TX_DROP

From: Bob Copeland <me@...copeland.com>

[ 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 d8fddd88bf46..a17a56032a21 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1837,7 +1837,7 @@ 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