sh_eth: fix napi_{en|dis}able() calls racing against interrupts

While implementing NAPI for the driver, I overlooked the race conditions where
interrupt  handler might have called napi_schedule_prep() before napi_enable()
was called or after napi_disable() was called. If RX interrupt happens, this
would cause the endless interrupts and messages like:

sh-eth eth0: ignoring interrupt, status 0x00040000, mask 0x01ff009f.

The interrupt wouldn't even be masked by the kernel eventually since the handler
would return IRQ_HANDLED all the time.

As a fix, move napi_enable() call before request_irq() call and napi_disable()
call after free_irq() call.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 5 deletions

diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c
index 1ccd5959c0bf..3426d32a1803 100644
--- a/drivers/net/ethernet/renesas/sh_eth.c
+++ b/drivers/net/ethernet/renesas/sh_eth.c
@@ -1857,11 +1857,13 @@ static int sh_eth_open(struct net_device *ndev)
 
         pm_runtime_get_sync(&mdp->pdev->dev);
 
+        napi_enable(&mdp->napi);
+
         ret = request_irq(ndev->irq, sh_eth_interrupt,
                           mdp->cd->irq_flags, ndev->name, ndev);
         if (ret) {
                 dev_err(&ndev->dev, "Can not assign IRQ number\n");
-                return ret;
+                goto out_napi_off;
         }
 
         /* Descriptor set */
@@ -1879,12 +1881,12 @@ static int sh_eth_open(struct net_device *ndev)
         if (ret)
                 goto out_free_irq;
 
-        napi_enable(&mdp->napi);
-
         return ret;
 
 out_free_irq:
         free_irq(ndev->irq, ndev);
+out_napi_off:
+        napi_disable(&mdp->napi);
         pm_runtime_put_sync(&mdp->pdev->dev);
         return ret;
 }
@@ -1976,8 +1978,6 @@ static int sh_eth_close(struct net_device *ndev)
 {
         struct sh_eth_private *mdp = netdev_priv(ndev);
 
-        napi_disable(&mdp->napi);
-
         netif_stop_queue(ndev);
 
         /* Disable interrupts by clearing the interrupt mask. */
@@ -1995,6 +1995,8 @@ static int sh_eth_close(struct net_device *ndev)
 
         free_irq(ndev->irq, ndev);
 
+        napi_disable(&mdp->napi);
+
         /* Free all the skbuffs in the Rx queue. */
         sh_eth_ring_free(ndev);