netdev - Re: [PATCH] net: fix problem in dequeuing from input_pkt

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Message-ID: <AANLkTinZHzZykWYWu9vOmK5ydtcB6ToVBKG1RKYSuSn4@mail.gmail.com>
Date:	Thu, 20 May 2010 08:09:50 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	davem@...emloft.net, eric.dumazet@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH] net: fix problem in dequeuing from input_pkt_queue

On Thu, May 20, 2010 at 7:58 AM, Tom Herbert <therbert@...gle.com> wrote:
>>>        napi->weight = weight_p;
>>> -       local_irq_disable();
>>>        while (work < quota) {
>>>                struct sk_buff *skb;
>>>                unsigned int qlen;
>>>
>>>                while ((skb = __skb_dequeue(&sd->process_queue))) {
>>> -                       local_irq_enable();
>>
>> we need to keep local irq disabled. If not, flush_backlog may be
>> called, and it will access sd->process_queue.
>>
>
> It should be okay?  process_backlog only runs in softirq so bottom
> halves are already disabled, and I don't think flush_backlog runs out
> of an interrupt.
>

Oh no. It is an IRQ handler.

  on_each_cpu(flush_backlog, dev, 1);
...
int on_each_cpu(void (*func) (void *info), void *info, int wait)
{
        int ret = 0;

        preempt_disable();
        ret = smp_call_function(func, info, wait);
        local_irq_disable();
        func(info);
        local_irq_enable();
        preempt_enable();
        return ret;
}

-- 
Regards，
Changli Gao(xiaosuo@...il.com)
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