[linux-yocto] [PATCH] Revert "igb: reduce CPU0 latency when updating statistics"

[zhe.he at windriver.com]

From: Jeff Kirsher <jeffrey.t.kirsher at intel.com>

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 <davej at codemonkey.org.uk>
CC: Cong Wang <xiyou.wangcong at gmail.com>
CC: Jan Jablonsky <jan.jablonsky at thalesgroup.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher at intel.com>
Signed-off-by: David S. Miller <davem at davemloft.net>

commit 5642e27bf6a935c1d0d9149e83d625dfba286463 upstream

Before syncing up with 5.0-rc3, it's worth backporting this patch which fixes
the following serious crash.

BUG: sleeping function called from invalid context at kernel/locking/mutex.c:254
in_atomic(): 0, irqs_disabled(): 0, pid: 7867, name: ifconfig
Preemption disabled at:
[<ffffffffa24962ce>] memcg_kmem_put_cache+0x2e/0x70
---- snip ----
Call Trace:
 dump_stack+0x4f/0x6a
 ? memcg_kmem_put_cache+0x2e/0x70
 ___might_sleep.cold.17+0xd9/0xea
 __might_sleep+0x4a/0x80
 mutex_lock+0x20/0x40
 igb_get_stats64+0x2c/0x60
 dev_get_stats+0x3f/0xa0
 dev_seq_printf_stats+0x37/0xe0
 dev_seq_show+0x14/0x30
 seq_read+0x2d3/0x3e0
 proc_reg_read+0x3e/0x60
 __vfs_read+0x3a/0x180
 ? security_file_permission+0x9c/0xf0
 vfs_read+0xa1/0x160
 ksys_read+0x55/0xc0
 __x64_sys_read+0x1a/0x20
 do_syscall_64+0x4d/0xf0
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Signed-off-by: He Zhe <zhe.he at windriver.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 fe1592a..ca54e26 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 7426060..c576710 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 87bdf16..7137e7f 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;
@@ -3840,7 +3840,7 @@ 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:
@@ -5406,9 +5406,9 @@ 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];
@@ -6235,10 +6235,10 @@ 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);
 }
 
 /**
-- 
2.7.4