linux-kernel - [PATCH 5.11 073/210] mac80211: fix time-is-after bug in mlme

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Message-Id: <20210412084018.451571727@linuxfoundation.org>
Date:   Mon, 12 Apr 2021 10:39:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ben Greear <greearb@...delatech.com>,
        Felix Fietkau <nbd@....name>,
        Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH 5.11 073/210] mac80211: fix time-is-after bug in mlme

From: Ben Greear <greearb@...delatech.com>

commit 7d73cd946d4bc7d44cdc5121b1c61d5d71425dea upstream.

The incorrect timeout check caused probing to happen when it did
not need to happen.  This in turn caused tx performance drop
for around 5 seconds in ath10k-ct driver.  Possibly that tx drop
is due to a secondary issue, but fixing the probe to not happen
when traffic is running fixes the symptom.

Signed-off-by: Ben Greear <greearb@...delatech.com>
Fixes: 9abf4e49830d ("mac80211: optimize station connection monitor")
Acked-by: Felix Fietkau <nbd@....name>
Link: https://lore.kernel.org/r/20210330230749.14097-1-greearb@candelatech.com
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/mac80211/mlme.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -4707,7 +4707,10 @@ static void ieee80211_sta_conn_mon_timer
 		timeout = sta->rx_stats.last_rx;
 	timeout += IEEE80211_CONNECTION_IDLE_TIME;
 
-	if (time_is_before_jiffies(timeout)) {
+	/* If timeout is after now, then update timer to fire at
+	 * the later date, but do not actually probe at this time.
+	 */
+	if (time_is_after_jiffies(timeout)) {
 		mod_timer(&ifmgd->conn_mon_timer, round_jiffies_up(timeout));
 		return;
 	}