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SubjectRe: [GIT]: Networking


Eric Dumazet wrote:
> 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)
>
>
> Oh well this patch was soooo stupid, sorry Ingo.
>
>
> We might have a race in napi_schedule(), leaving interrupts disabled forever.
> I cannot test this patch, I dont have the hardware...
>
> Thanks
>
> diff --git a/drivers/net/forcedeth.c b/drivers/net/forcedeth.c
> index 1094d29..3b4e076 100644
> --- a/drivers/net/forcedeth.c
> +++ b/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);
> + }

Yes, good catch. There is a race condition here with napi poll.

I would prefer to do the following to keep the code simple and clean.

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
> {
--
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