Date: Sat, 12 Apr 2014 02:59:23 +0800 From: Julian Elischer <julian@freebsd.org> To: freebsd-net@freebsd.org Subject: Re: Preventing ng_callout() timeouts to trigger packet queuing Message-ID: <53483B8B.7030409@freebsd.org> In-Reply-To: <5345BAE7.4010501@gmail.com> References: <53459C96.5040304@gmail.com> <5345BAE7.4010501@gmail.com>
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disclaimer: I'm not looking at the code now.. I want to go to bed: :-)
When I wrote that code, the idea was that even a direct node execution
should become a queuing operation if there was already something else
on the queue. so in that model packets were not supposed to get
re-ordered. does that not still work?
Either that, or you need to explain the problem to me a bit better..
On 4/10/14, 5:25 AM, Karim Fodil-Lemelin wrote:
> Hi,
>
> Below is a revised patch for this issue. It accounts for nodes or
> hooks that explicitly need to be queuing:
>
> @@ -3632,7 +3632,12 @@ ng_callout(struct callout *c, node_p node,
> hook_p hook, int ticks,
> if ((item = ng_alloc_item(NGQF_FN, NG_NOFLAGS)) == NULL)
> return (ENOMEM);
>
> - item->el_flags |= NGQF_WRITER;
> + if ((node->nd_flags & NGF_FORCE_WRITER) ||
> + (hook && (hook->hk_flags & HK_FORCE_WRITER)))
> + item->el_flags |= NGQF_WRITER;
> + else
> + item->el_flags |= NGQF_READER;
> +
> NG_NODE_REF(node); /* and one for the item */
> NGI_SET_NODE(item, node);
> if (hook) {
>
> Regards,
>
> Karim.
>
> On 09/04/2014 3:16 PM, Karim Fodil-Lemelin wrote:
>> Hi List,
>>
>> I'm calling out to the general wisdom ... I have seen an issue in
>> netgraph where, if called, a callout routine registered by
>> ng_callout() will trigger packet queuing inside the worklist of
>> netgraph since ng_callout() makes my node suddenly a WRITER node
>> (therefore non reentrant) for the duration of the call.
>>
>> So as soon as the callout function returns, all following packets
>> will get directly passed to the node again and when the ngintr
>> thread gets executed then only then will I get the queued packets.
>> This introduces out of order packets in the flow. I am using the
>> current patch below to solve the issue and I am wondering if there
>> is anything wrong with it (and maybe contribute back :):
>>
>>
>> @@ -3632,7 +3632,7 @@ ng_callout(struct callout *c, node_p node,
>> hook_p hook, int ticks,
>> if ((item = ng_alloc_item(NGQF_FN, NG_NOFLAGS)) == NULL)
>> return (ENOMEM);
>>
>> - item->el_flags |= NGQF_WRITER;
>> + item->el_flags = NGQF_READER;
>> NG_NODE_REF(node); /* and one for the item */
>> NGI_SET_NODE(item, node);
>> if (hook) {
>>
>>
>> Best regards,
>>
>> Karim.
>> _______________________________________________
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>
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