stmmac: fix sleep inside atomic

We cannot use spinlock when kmalloc is invoked with
GFP_KERNEL flag because it can sleep.
So this patch reviews the usage of spinlock within the
stmmac_resume function avoing this bug.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Reported-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/stmmac/stmmac_main.c

@@ -1865,15 +1865,15 @@ static int stmmac_resume(struct platform_device *pdev)
 	if (!netif_running(dev))
 		return 0;
 
-	spin_lock(&priv->lock);
-
 	if (priv->shutdown) {
 		/* Re-open the interface and re-init the MAC/DMA
-		   and the rings. */
+		   and the rings (i.e. on hibernation stage) */
 		stmmac_open(dev);
-		goto out_resume;
+		return 0;
 	}
 
+	spin_lock(&priv->lock);
+
 	/* Power Down bit, into the PM register, is cleared
 	 * automatically as soon as a magic packet or a Wake-up frame
 	 * is received. Anyway, it's better to manually clear
@@ -1901,7 +1901,6 @@ static int stmmac_resume(struct platform_device *pdev)
 
 	netif_start_queue(dev);
 
-out_resume:
 	spin_unlock(&priv->lock);
 	return 0;
 }