sfc: PTP: Moderate log message on event queue overflow

Limit syslog flood if a PTP packet storm occurs.

Fixes: 7c236c43b838 ('sfc: Add support for IEEE-1588 PTP')
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

1 files changed, 21 insertions, 2 deletions

diff --git a/drivers/net/ethernet/sfc/ptp.c b/drivers/net/ethernet/sfc/ptp.c
index 93a61a157d10..8b2cf783217c 100644
--- a/drivers/net/ethernet/sfc/ptp.c
+++ b/drivers/net/ethernet/sfc/ptp.c
@@ -220,6 +220,7 @@ struct efx_ptp_timeset {
  * @evt_list: List of MC receive events awaiting packets
  * @evt_free_list: List of free events
  * @evt_lock: Lock for manipulating evt_list and evt_free_list
+ * @evt_overflow: Boolean indicating that event list has overflowed
  * @rx_evts: Instantiated events (on evt_list and evt_free_list)
  * @workwq: Work queue for processing pending PTP operations
  * @work: Work task
@@ -270,6 +271,7 @@ struct efx_ptp_data {
         struct list_head evt_list;
         struct list_head evt_free_list;
         spinlock_t evt_lock;
+        bool evt_overflow;
         struct efx_ptp_event_rx rx_evts[MAX_RECEIVE_EVENTS];
         struct workqueue_struct *workwq;
         struct work_struct work;
@@ -635,6 +637,11 @@ static void efx_ptp_drop_time_expired_events(struct efx_nic *efx)
                         }
                 }
         }
+        /* If the event overflow flag is set and the event list is now empty
+         * clear the flag to re-enable the overflow warning message.
+         */
+        if (ptp->evt_overflow && list_empty(&ptp->evt_list))
+                ptp->evt_overflow = false;
         spin_unlock_bh(&ptp->evt_lock);
 }
 
@@ -676,6 +683,11 @@ static enum ptp_packet_state efx_ptp_match_rx(struct efx_nic *efx,
                         break;
                 }
         }
+        /* If the event overflow flag is set and the event list is now empty
+         * clear the flag to re-enable the overflow warning message.
+         */
+        if (ptp->evt_overflow && list_empty(&ptp->evt_list))
+                ptp->evt_overflow = false;
         spin_unlock_bh(&ptp->evt_lock);
 
         return rc;
@@ -809,6 +821,7 @@ static int efx_ptp_stop(struct efx_nic *efx)
         list_for_each_safe(cursor, next, &efx->ptp_data->evt_list) {
                 list_move(cursor, &efx->ptp_data->evt_free_list);
         }
+        ptp->evt_overflow = false;
         spin_unlock_bh(&efx->ptp_data->evt_lock);
 
         return rc;
@@ -901,6 +914,7 @@ static int efx_ptp_probe_channel(struct efx_channel *channel)
         spin_lock_init(&ptp->evt_lock);
         for (pos = 0; pos < MAX_RECEIVE_EVENTS; pos++)
                 list_add(&ptp->rx_evts[pos].link, &ptp->evt_free_list);
+        ptp->evt_overflow = false;
 
         ptp->phc_clock_info.owner = THIS_MODULE;
         snprintf(ptp->phc_clock_info.name,
@@ -1299,8 +1313,13 @@ static void ptp_event_rx(struct efx_nic *efx, struct efx_ptp_data *ptp)
                 list_add_tail(&evt->link, &ptp->evt_list);
 
                 queue_work(ptp->workwq, &ptp->work);
-        } else {
-                netif_err(efx, rx_err, efx->net_dev, "No free PTP event");
+        } else if (!ptp->evt_overflow) {
+                /* Log a warning message and set the event overflow flag.
+                 * The message won't be logged again until the event queue
+                 * becomes empty.
+                 */
+                netif_err(efx, rx_err, efx->net_dev, "PTP event queue overflow\n");
+                ptp->evt_overflow = true;
         }
         spin_unlock_bh(&ptp->evt_lock);
 }