From: Oliver Hartkopp <socketcan@hartkopp.net>
Commit 80b5f90158d1 ("can: statistics: use atomic access in hot path")
introduced local snapshots of the statistics counters at the beginning
of can_stat_update(). When can_init_stats() resets the statistics, these
stale pre-reset snapshots are still used for the following total/current
/max calculations and overwrite the freshly reset values. Additionally a
jiffies tick between the snapshot and the reset could trigger a second
can_init_stats() call.
Merge the reset conditions into a single check and skip the calculation
for the current interval when the statistics have been reset.
Fixes: 80b5f90158d1 ("can: statistics: use atomic access in hot path")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20261020203257.230955-3-socketcan@hartkopp.net (local)
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
net/can/proc.c | 30 ++++++++++++------------------
1 file changed, 12 insertions(+), 18 deletions(-)
diff --git a/net/can/proc.c b/net/can/proc.c
index 70104f13077e..fb144d2adc35 100644
--- a/net/can/proc.c
+++ b/net/can/proc.c
@@ -149,25 +149,18 @@ void can_stat_update(struct timer_list *t)
long tx_frames_delta = atomic_long_xchg(&pkg_stats->tx_frames_delta, 0);
long matches_delta = atomic_long_xchg(&pkg_stats->matches_delta, 0);
- /* restart counting in timer context on user request */
- if (user_reset)
- can_init_stats(net);
-
- /* restart counting on jiffies overflow */
- if (j < pkg_stats->jiffies_init)
- can_init_stats(net);
-
- /* prevent overflow in calc_rate() */
- if (rx_frames > (LONG_MAX / HZ))
- can_init_stats(net);
-
- /* prevent overflow in calc_rate() */
- if (tx_frames > (LONG_MAX / HZ))
- can_init_stats(net);
-
- /* matches overflow - very improbable */
- if (matches > (LONG_MAX / 100))
+ /*
+ * Restart counting in timer context on user request, on jiffies
+ * overflow or to prevent overflows in calc_rate() and in the
+ * match ratio calculation. The local snapshots are stale after
+ * the reset, so skip the calculation for this interval.
+ */
+ if (user_reset || j < pkg_stats->jiffies_init ||
+ rx_frames > (LONG_MAX / HZ) || tx_frames > (LONG_MAX / HZ) ||
+ matches > (LONG_MAX / 100)) {
can_init_stats(net);
+ goto out;
+ }
/* calc total values */
if (rx_frames)@@ -196,6 +189,7 @@ void can_stat_update(struct timer_list *t)
if (pkg_stats->max_rx_match_ratio < pkg_stats->current_rx_match_ratio)
pkg_stats->max_rx_match_ratio = pkg_stats->current_rx_match_ratio;
+out:
/* restart timer (one second) */
mod_timer(&net->can.stattimer, round_jiffies(jiffies + HZ));
}
--
2.53.0