[net] Revert "igb: reduce CPU0 latency when updating statistics"

[Jeff Kirsher]

This reverts commit 59361316afcb08569af21e1af83e89c7051c055a.

Due to problems found in additional testing, this causes an illegal
context switch in the RCU read-side critical section.

CC: Dave Jones <da...@codemonkey.org.uk>
CC: Cong Wang <xiyou.wangc...@gmail.com>
CC: Jan Jablonsky <jan.jablon...@thalesgroup.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirs...@intel.com>
---
 drivers/net/ethernet/intel/igb/igb.h         |  2 +-
 drivers/net/ethernet/intel/igb/igb_ethtool.c |  4 ++--
 drivers/net/ethernet/intel/igb/igb_main.c    | 14 +++++++-------
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb.h 
b/drivers/net/ethernet/intel/igb/igb.h
index fe1592ae8769..ca54e268d157 100644
--- a/drivers/net/ethernet/intel/igb/igb.h
+++ b/drivers/net/ethernet/intel/igb/igb.h
@@ -515,7 +515,7 @@ struct igb_adapter {
        /* OS defined structs */
        struct pci_dev *pdev;
 
-       struct mutex stats64_lock;
+       spinlock_t stats64_lock;
        struct rtnl_link_stats64 stats64;
 
        /* structs defined in e1000_hw.h */
diff --git a/drivers/net/ethernet/intel/igb/igb_ethtool.c 
b/drivers/net/ethernet/intel/igb/igb_ethtool.c
index 7426060b678f..c57671068245 100644
--- a/drivers/net/ethernet/intel/igb/igb_ethtool.c
+++ b/drivers/net/ethernet/intel/igb/igb_ethtool.c
@@ -2295,7 +2295,7 @@ static void igb_get_ethtool_stats(struct net_device 
*netdev,
        int i, j;
        char *p;
 
-       mutex_lock(&adapter->stats64_lock);
+       spin_lock(&adapter->stats64_lock);
        igb_update_stats(adapter);
 
        for (i = 0; i < IGB_GLOBAL_STATS_LEN; i++) {
@@ -2338,7 +2338,7 @@ static void igb_get_ethtool_stats(struct net_device 
*netdev,
                } while (u64_stats_fetch_retry_irq(&ring->rx_syncp, start));
                i += IGB_RX_QUEUE_STATS_LEN;
        }
-       mutex_unlock(&adapter->stats64_lock);
+       spin_unlock(&adapter->stats64_lock);
 }
 
 static void igb_get_strings(struct net_device *netdev, u32 stringset, u8 *data)
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c 
b/drivers/net/ethernet/intel/igb/igb_main.c
index 509f9d3fba00..05caf569c307 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -2203,9 +2203,9 @@ void igb_down(struct igb_adapter *adapter)
        del_timer_sync(&adapter->phy_info_timer);
 
        /* record the stats before reset*/
-       mutex_lock(&adapter->stats64_lock);
+       spin_lock(&adapter->stats64_lock);
        igb_update_stats(adapter);
-       mutex_unlock(&adapter->stats64_lock);
+       spin_unlock(&adapter->stats64_lock);
 
        adapter->link_speed = 0;
        adapter->link_duplex = 0;
@@ -3847,7 +3847,7 @@ static int igb_sw_init(struct igb_adapter *adapter)
        adapter->min_frame_size = ETH_ZLEN + ETH_FCS_LEN;
 
        spin_lock_init(&adapter->nfc_lock);
-       mutex_init(&adapter->stats64_lock);
+       spin_lock_init(&adapter->stats64_lock);
 #ifdef CONFIG_PCI_IOV
        switch (hw->mac.type) {
        case e1000_82576:
@@ -5413,9 +5413,9 @@ static void igb_watchdog_task(struct work_struct *work)
                }
        }
 
-       mutex_lock(&adapter->stats64_lock);
+       spin_lock(&adapter->stats64_lock);
        igb_update_stats(adapter);
-       mutex_unlock(&adapter->stats64_lock);
+       spin_unlock(&adapter->stats64_lock);
 
        for (i = 0; i < adapter->num_tx_queues; i++) {
                struct igb_ring *tx_ring = adapter->tx_ring[i];
@@ -6242,10 +6242,10 @@ static void igb_get_stats64(struct net_device *netdev,
 {
        struct igb_adapter *adapter = netdev_priv(netdev);
 
-       mutex_lock(&adapter->stats64_lock);
+       spin_lock(&adapter->stats64_lock);
        igb_update_stats(adapter);
        memcpy(stats, &adapter->stats64, sizeof(*stats));
-       mutex_unlock(&adapter->stats64_lock);
+       spin_unlock(&adapter->stats64_lock);
 }
 
 /**
-- 
2.20.1