[PATCH net-next] qlcnic: Optimize performance by replacing rw_lock with spinlock

[Yu-Chun Lin]

The 'crb_lock', an rwlock, is only used by writers, making it functionally
equivalent to a spinlock.

According to Documentation/locking/spinlocks.rst:

"Reader-writer locks require more atomic memory operations than simple
spinlocks. Unless the reader critical section is long, you are better
off just using spinlocks."

Since read_lock() is never called, switching to a spinlock reduces
overhead and improves efficiency.

Signed-off-by: Yu-Chun Lin <eleanor15x@xxxxxxxxx>
---
 drivers/net/ethernet/qlogic/qlcnic/qlcnic.h      | 2 +-
 drivers/net/ethernet/qlogic/qlcnic/qlcnic_hw.c   | 8 ++++----
 drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c | 2 +-
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic.h b/drivers/net/ethernet/qlogic/qlcnic/qlcnic.h
index 3d0b5cd978cb..b8c8bc572042 100644
--- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic.h
+++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic.h
@@ -470,7 +470,7 @@ struct qlcnic_hardware_context {
 
 	unsigned long pci_len0;
 
-	rwlock_t crb_lock;
+	spinlock_t crb_lock;
 	struct mutex mem_lock;
 
 	u8 revision_id;
diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_hw.c b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_hw.c
index ae4ee0326ee1..7b9bd0938229 100644
--- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_hw.c
+++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_hw.c
@@ -1185,13 +1185,13 @@ int qlcnic_82xx_hw_write_wx_2M(struct qlcnic_adapter *adapter, ulong off,
 
 	if (rv > 0) {
 		/* indirect access */
-		write_lock_irqsave(&adapter->ahw->crb_lock, flags);
+		spin_lock_irqsave(&adapter->ahw->crb_lock, flags);
 		crb_win_lock(adapter);
 		rv = qlcnic_pci_set_crbwindow_2M(adapter, off);
 		if (!rv)
 			writel(data, addr);
 		crb_win_unlock(adapter);
-		write_unlock_irqrestore(&adapter->ahw->crb_lock, flags);
+		spin_unlock_irqrestore(&adapter->ahw->crb_lock, flags);
 		return rv;
 	}
 
@@ -1216,12 +1216,12 @@ int qlcnic_82xx_hw_read_wx_2M(struct qlcnic_adapter *adapter, ulong off,
 
 	if (rv > 0) {
 		/* indirect access */
-		write_lock_irqsave(&adapter->ahw->crb_lock, flags);
+		spin_lock_irqsave(&adapter->ahw->crb_lock, flags);
 		crb_win_lock(adapter);
 		if (!qlcnic_pci_set_crbwindow_2M(adapter, off))
 			data = readl(addr);
 		crb_win_unlock(adapter);
-		write_unlock_irqrestore(&adapter->ahw->crb_lock, flags);
+		spin_unlock_irqrestore(&adapter->ahw->crb_lock, flags);
 		return data;
 	}
 
diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c
index eb69121df726..5389e441fdae 100644
--- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c
+++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c
@@ -2508,7 +2508,7 @@ qlcnic_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	else if (qlcnic_mac_learn == DRV_MAC_LEARN)
 		adapter->drv_mac_learn = true;
 
-	rwlock_init(&adapter->ahw->crb_lock);
+	spin_lock_init(&adapter->ahw->crb_lock);
 	mutex_init(&adapter->ahw->mem_lock);
 
 	INIT_LIST_HEAD(&adapter->mac_list);
-- 
2.43.0