eth: fbnic: add locking support for hw stats

This patch adds lock protection for the hardware statistics for fbnic.
The hardware statistics access via ndo_get_stats64 is not protected by
the rtnl_lock(). Since these stats can be accessed from different places
in the code such as service task, ethtool, Q-API, and net_device_ops, a
lock-less approach can lead to races.

Note that this patch is not a fix rather, just a prep for the subsequent
changes in this series.

Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Mohsin Bashir <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

Author: Mohsin Bashir

drivers/net/ethernet/meta/fbnic/fbnic.h

@@ -81,6 +81,9 @@ struct fbnic_dev {
 
 	/* Local copy of hardware statistics */
 	struct fbnic_hw_stats hw_stats;
+
+	/* Lock protecting access to hw_stats */
+	spinlock_t hw_stats_lock;
 };
 
 /* Reserve entry 0 in the MSI-X "others" array until we have filled all

drivers/net/ethernet/meta/fbnic/fbnic_hw_stats.c

@@ -203,18 +203,28 @@ static void fbnic_get_pcie_stats_asic64(struct fbnic_dev *fbd,
 
 void fbnic_reset_hw_stats(struct fbnic_dev *fbd)
 {
+	spin_lock(&fbd->hw_stats_lock);
 	fbnic_reset_rpc_stats(fbd, &fbd->hw_stats.rpc);
 	fbnic_reset_pcie_stats_asic(fbd, &fbd->hw_stats.pcie);
+	spin_unlock(&fbd->hw_stats_lock);
 }
 
-void fbnic_get_hw_stats32(struct fbnic_dev *fbd)
+static void __fbnic_get_hw_stats32(struct fbnic_dev *fbd)
 {
 	fbnic_get_rpc_stats32(fbd, &fbd->hw_stats.rpc);
 }
 
-void fbnic_get_hw_stats(struct fbnic_dev *fbd)
+void fbnic_get_hw_stats32(struct fbnic_dev *fbd)
 {
-	fbnic_get_hw_stats32(fbd);
+	spin_lock(&fbd->hw_stats_lock);
+	__fbnic_get_hw_stats32(fbd);
+	spin_unlock(&fbd->hw_stats_lock);
+}
 
+void fbnic_get_hw_stats(struct fbnic_dev *fbd)
+{
+	spin_lock(&fbd->hw_stats_lock);
+	__fbnic_get_hw_stats32(fbd);
 	fbnic_get_pcie_stats_asic64(fbd, &fbd->hw_stats.pcie);
+	spin_unlock(&fbd->hw_stats_lock);
 }

drivers/net/ethernet/meta/fbnic/fbnic_pci.c

@@ -292,6 +292,7 @@ static int fbnic_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 
 	fbnic_devlink_register(fbd);
 	fbnic_dbg_fbd_init(fbd);
+	spin_lock_init(&fbd->hw_stats_lock);
 
 	/* Capture snapshot of hardware stats so netdev can calculate delta */
 	fbnic_reset_hw_stats(fbd);