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: <551B0274.1010900@hartkopp.net>
Date:	Tue, 31 Mar 2015 22:24:20 +0200
From:	Oliver Hartkopp <socketcan@...tkopp.net>
To:	Marc Kleine-Budde <mkl@...gutronix.de>, 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 31.03.2015 14:32, Marc Kleine-Budde wrote:
> On 03/30/2015 12:41 PM, Oliver Hartkopp wrote:
>> Please check out
>>
>> https://www.kernel.org/pub/linux/kernel/people/rusty/kernel-locking/
>>
>> And especially
>> https://www.kernel.org/pub/linux/kernel/people/rusty/kernel-locking/x173.html#LOCK-SOFTIRQS-SAME
>>
>> When a softirq processes an incoming skb this remains on that selected CPU.
>
> Okay, I was not sure about this. What about preempt_rt?
>

I don't care :-)

There are so many implementations that rely on this per-CPU stuff that we can 
assume preempt_rt takes care of it (e.g. with locking or reducing CPU cores, etc)

>> Putting a struct into these percpu handling can be done - but does it increase
>> the readability in this case?
>
> It saves ressources, 1 pointer instead of 3 (considering both of your
> patches) and only 1 allocation.

Yes. I did some more code reading, created a struct for it and omitted the 
initialization as alloc_percpu returns an already zero'ed memory region.

Will send tomorrow morning.

Regards,
Oliver
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