netdev - Re: RPS patch questions

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Message-ID: <1282742210.2487.277.camel@edumazet-laptop>
Date:	Wed, 25 Aug 2010 15:16:50 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Lal <learner.kernel@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: RPS patch questions

Le mercredi 25 août 2010 à 18:05 +0530, Lal a écrit :
> I am evaluating RPS patch from Tom Herbert. I have some questions
> regarding this patch.
> 
> 1. Can __smp_call_function_single be called from bottom half handler?
> I presume, yes.
> 

right.

> 2. I am working on 2.6.21 kernel which have neither
> __smp_call_function_single nor smp_call_function_single. I used
> smp_call_function_single from some other kernel version but this too
> can not be called from bottom half handler (just like
> smp_call_function). Did somebody try to write such function for 2.6.21
> (or older kernel) which can be called from bottom halves?

2.6.21 is too old for us ;)

> 
> 3. One option I've is to upgrade to 2.6.27 kernel which has
> __smp_call_function_single. I see a comment that this function must
> not be called with interrupt disabled. Does it mean it can be called
> from bottom half handler?
> 

__smp_call_function_single must be called with hard irqs enabled.

bottom half handlers (softirqs) do run with hard irqs enabled.



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