RPS patch questions

RPS patch questions

[Lal]

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.

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?

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?

Thanks
Lal

Re: RPS patch questions

[Eric Dumazet]

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.