igc: Add lock to safeguard global Qbv variables

Access to shared variables through hrtimer requires locking in order
to protect the variables because actions to write into these variables
(oper_gate_closed, admin_gate_closed, and qbv_transition) might potentially
occur simultaneously. This patch provides a locking mechanisms to avoid
such scenarios.

Fixes: 175c241 ("igc: Fix TX Hang issue when QBV Gate is closed")
Suggested-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://lore.kernel.org/r/20230807205129.3129346-1-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/intel/igc/igc.h

@@ -195,6 +195,10 @@ struct igc_adapter {
 	u32 qbv_config_change_errors;
 	bool qbv_transition;
 	unsigned int qbv_count;
+	/* Access to oper_gate_closed, admin_gate_closed and qbv_transition
+	 * are protected by the qbv_tx_lock.
+	 */
+	spinlock_t qbv_tx_lock;
 
 	/* OS defined structs */
 	struct pci_dev *pdev;

drivers/net/ethernet/intel/igc/igc_main.c

@@ -4801,6 +4801,7 @@ static int igc_sw_init(struct igc_adapter *adapter)
 	adapter->nfc_rule_count = 0;
 
 	spin_lock_init(&adapter->stats64_lock);
+	spin_lock_init(&adapter->qbv_tx_lock);
 	/* Assume MSI-X interrupts, will be checked during IRQ allocation */
 	adapter->flags |= IGC_FLAG_HAS_MSIX;
 
@@ -6119,15 +6120,15 @@ static int igc_tsn_enable_launchtime(struct igc_adapter *adapter,
 	return igc_tsn_offload_apply(adapter);
 }
 
-static int igc_tsn_clear_schedule(struct igc_adapter *adapter)
+static int igc_qbv_clear_schedule(struct igc_adapter *adapter)
 {
+	unsigned long flags;
 	int i;
 
 	adapter->base_time = 0;
 	adapter->cycle_time = NSEC_PER_SEC;
 	adapter->taprio_offload_enable = false;
 	adapter->qbv_config_change_errors = 0;
-	adapter->qbv_transition = false;
 	adapter->qbv_count = 0;
 
 	for (i = 0; i < adapter->num_tx_queues; i++) {
@@ -6136,10 +6137,28 @@ static int igc_tsn_clear_schedule(struct igc_adapter *adapter)
 		ring->start_time = 0;
 		ring->end_time = NSEC_PER_SEC;
 		ring->max_sdu = 0;
+	}
+
+	spin_lock_irqsave(&adapter->qbv_tx_lock, flags);
+
+	adapter->qbv_transition = false;
+
+	for (i = 0; i < adapter->num_tx_queues; i++) {
+		struct igc_ring *ring = adapter->tx_ring[i];
+
 		ring->oper_gate_closed = false;
 		ring->admin_gate_closed = false;
 	}
 
+	spin_unlock_irqrestore(&adapter->qbv_tx_lock, flags);
+
+	return 0;
+}
+
+static int igc_tsn_clear_schedule(struct igc_adapter *adapter)
+{
+	igc_qbv_clear_schedule(adapter);
+
 	return 0;
 }
 
@@ -6150,6 +6169,7 @@ static int igc_save_qbv_schedule(struct igc_adapter *adapter,
 	struct igc_hw *hw = &adapter->hw;
 	u32 start_time = 0, end_time = 0;
 	struct timespec64 now;
+	unsigned long flags;
 	size_t n;
 	int i;
 
@@ -6217,6 +6237,8 @@ static int igc_save_qbv_schedule(struct igc_adapter *adapter,
 		start_time += e->interval;
 	}
 
+	spin_lock_irqsave(&adapter->qbv_tx_lock, flags);
+
 	/* Check whether a queue gets configured.
 	 * If not, set the start and end time to be end time.
 	 */
@@ -6241,6 +6263,8 @@ static int igc_save_qbv_schedule(struct igc_adapter *adapter,
 		}
 	}
 
+	spin_unlock_irqrestore(&adapter->qbv_tx_lock, flags);
+
 	for (i = 0; i < adapter->num_tx_queues; i++) {
 		struct igc_ring *ring = adapter->tx_ring[i];
 		struct net_device *dev = adapter->netdev;
@@ -6619,8 +6643,11 @@ static enum hrtimer_restart igc_qbv_scheduling_timer(struct hrtimer *timer)
 {
 	struct igc_adapter *adapter = container_of(timer, struct igc_adapter,
 						   hrtimer);
+	unsigned long flags;
 	unsigned int i;
 
+	spin_lock_irqsave(&adapter->qbv_tx_lock, flags);
+
 	adapter->qbv_transition = true;
 	for (i = 0; i < adapter->num_tx_queues; i++) {
 		struct igc_ring *tx_ring = adapter->tx_ring[i];
@@ -6633,6 +6660,9 @@ static enum hrtimer_restart igc_qbv_scheduling_timer(struct hrtimer *timer)
 		}
 	}
 	adapter->qbv_transition = false;
+
+	spin_unlock_irqrestore(&adapter->qbv_tx_lock, flags);
+
 	return HRTIMER_NORESTART;
 }