From: Oliver Hartkopp 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 Link: https://patch.msgid.link/20261020203257.230955-3-socketcan@hartkopp.net Signed-off-by: Marc Kleine-Budde --- 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