Re: [GIT]: Networking

Eric Dumazet
2009-07-02T22:33:11Z

Ayaz Abdulla a écrit :
>
>
> 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);

CC trimmed down to network devs only :)

It would be racy too ...

check drivers/net/amd8111e.c, drivers/net/natsemi.c ...

If this cpu inconditionaly calls writel(0, base + NvRegIrqMask);
while another cpu just called writel(np->irqmask, base + NvRegIrqMask),
we end with disabled interrupts ?