[PATCH] mac80211: fix time-is-after bug in mlme.

[PATCH] mac80211: fix time-is-after bug in mlme.

[greearb]

From: Ben Greear <greearb@candelatech.com>

This fixes commit:  mac80211: optimize station connection monitor
which came in in the 5.10 kernel.

This 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@candelatech.com>
---
 net/mac80211/mlme.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index c137a8b5d8e1..b06c76116d86 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -4729,7 +4729,10 @@ static void ieee80211_sta_conn_mon_timer(struct timer_list *t)
 		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;
 	}
-- 
2.20.1

Re: [PATCH] mac80211: fix time-is-after bug in mlme.

[Felix Fietkau]

On 2021-03-31 01:07, greearb@candelatech.com wrote:
> From: Ben Greear <greearb@candelatech.com>
> 
> This fixes commit:  mac80211: optimize station connection monitor
> which came in in the 5.10 kernel.
> 
> This 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@candelatech.com>
Acked-by: Felix Fietkau <nbd@nbd.name>

- Felix