forcedeth: Fix NAPI race.

Eric Dumazet a écrit :
> Ingo Molnar a écrit :
>>> The following changes since commit 52989765629e7d182b4f146050ebba0abf2cb0b7:
>>>   Linus Torvalds (1):
>>>         Merge git://git.kernel.org/.../davem/net-2.6
>>>
>>> are available in the git repository at:
>>>
>>>   master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6.git master
>> Hm, something in this lot quickly wrecked networking here - see the
>> tx timeout dump below. It starts with:
>>
>> [  351.004596] WARNING: at net/sched/sch_generic.c:246 dev_watchdog+0x10b/0x19c()
>> [  351.011815] Hardware name: System Product Name
>> [  351.016220] NETDEV WATCHDOG: eth0 (forcedeth): transmit queue 0 timed out
>>
>> Config attached. Unfortunately i've got no time to do bisection
>> today.
>
>
>
> forcedeth might have a problem, in its netif_wake_queue() logic, but
> I could not see why a recent patch could make this problem visible now.
>
> CPU0/1: AMD Athlon(tm) 64 X2 Dual Core Processor 3800+ stepping 02
> is not a new cpu either :)
>
> forcedeth uses an internal tx_stop without appropriate barrier.
>
> Could you try following patch ?
>
> (random guess as I dont have much time right now)

We might have a race in napi_schedule(), leaving interrupts disabled forever.
I cannot test this patch, I dont have the hardware...

Tested-by: Ingo Molnar <mingo@elte.hu>

Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/forcedeth.c

@@ -3514,11 +3514,13 @@ static irqreturn_t nv_nic_irq(int foo, void *data)
 	nv_msi_workaround(np);
 
 #ifdef CONFIG_FORCEDETH_NAPI
-	napi_schedule(&np->napi);
-
-	/* Disable furthur irq's
-	   (msix not enabled with napi) */
-	writel(0, base + NvRegIrqMask);
+	if (napi_schedule_prep(&np->napi)) {
+		/*
+		 * Disable further irq's (msix not enabled with napi)
+		 */
+		writel(0, base + NvRegIrqMask);
+		__napi_schedule(&np->napi);
+	}
 
 #else
 	do
@@ -3615,12 +3617,13 @@ static irqreturn_t nv_nic_irq_optimized(int foo, void *data)
 	nv_msi_workaround(np);
 
 #ifdef CONFIG_FORCEDETH_NAPI
-	napi_schedule(&np->napi);
-
-	/* Disable furthur irq's
-	   (msix not enabled with napi) */
-	writel(0, base + NvRegIrqMask);
-
+	if (napi_schedule_prep(&np->napi)) {
+		/*
+		 * Disable further irq's (msix not enabled with napi)
+		 */
+		writel(0, base + NvRegIrqMask);
+		__napi_schedule(&np->napi);
+	}
 #else
 	do
 	{