netdev - Re: [PATCH RFC v2 1/2] can: fix multiple delivery of a single CAN frame for overlapping CAN filters

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Message-ID: <5519708E.3040002@hartkopp.net>
Date:	Mon, 30 Mar 2015 17:49:34 +0200
From:	Oliver Hartkopp <socketcan@...tkopp.net>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	linux-can@...r.kernel.org
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH RFC v2 1/2] can: fix multiple delivery of a single CAN
 frame for overlapping CAN filters

On 30.03.2015 14:33, Sergei Shtylyov wrote:
> On 3/29/2015 9:09 PM, Oliver Hartkopp wrote:
>>
>> +    /* eliminate multiple filter matches for the same skb */
>> +    if (*this_cpu_ptr(ro->uniq_skb) == oskb &&
>> +        ktime_equal(*this_cpu_ptr(ro->uniq_tstamp), oskb->tstamp)) {
>> +            return;
>
>     Over-indented.
>

I was asked about that before. AFAIK the *skb is no unique identifier over a 
longer period of time. But together with the timestamp it becomes unique.
Or do you have a better solution to detect identical skbs?

CAN skbs do not have a (rx)hash so far and I wonder if it's worth to compute 
the hash in favor to check the *skb and the timestamp here ...


>> +
>> +    ro->uniq_tstamp = alloc_percpu(ktime_t);
>> +    if (unlikely(ro->uniq_tstamp == NULL)) {
>
>     !ro->uniq_tstamp is preferred in the networking code.
>

Ok. Will change that.

Best regards,
Oliver

> [...]
>
> WBR, Sergei
>

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