drivers/net: fixed drivers that support netpoll use ndo_start_xmit()

The NETPOLL API requires that interrupts remain disabled in
netpoll_send_skb(). The use of "A functions set" in the NETPOLL API
callbacks causes the interrupts to get enabled and can lead to kernel
instability.

The solution is to use "B functions set" to prevent the irqs from
getting enabled while in netpoll_send_skb().

A functions set:
local_irq_disable()/local_irq_enable()
spin_lock_irq()/spin_unlock_irq()
spin_trylock_irq()/spin_unlock_irq()

B functions set:
local_irq_save()/local_irq_restore()
spin_lock_irqsave()/spin_unlock_irqrestore()
spin_trylock_irqsave()/spin_unlock_irqrestore()

Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/net/mlx4/en_tx.c b/drivers/net/mlx4/en_tx.c
index 5a88b3f57693..62208401c4df 100644
--- a/drivers/net/mlx4/en_tx.c
+++ b/drivers/net/mlx4/en_tx.c
@@ -437,6 +437,7 @@ static inline void mlx4_en_xmit_poll(struct mlx4_en_priv *priv, int tx_ind)
 {
         struct mlx4_en_cq *cq = &priv->tx_cq[tx_ind];
         struct mlx4_en_tx_ring *ring = &priv->tx_ring[tx_ind];
+        unsigned long flags;
 
         /* If we don't have a pending timer, set one up to catch our recent
            post in case the interface becomes idle */
@@ -445,9 +446,9 @@ static inline void mlx4_en_xmit_poll(struct mlx4_en_priv *priv, int tx_ind)
 
         /* Poll the CQ every mlx4_en_TX_MODER_POLL packets */
         if ((++ring->poll_cnt & (MLX4_EN_TX_POLL_MODER - 1)) == 0)
-                if (spin_trylock_irq(&ring->comp_lock)) {
+                if (spin_trylock_irqsave(&ring->comp_lock, flags)) {
                         mlx4_en_process_tx_cq(priv->dev, cq);
-                        spin_unlock_irq(&ring->comp_lock);
+                        spin_unlock_irqrestore(&ring->comp_lock, flags);
                 }
 }