linux-kernel - Re: [PATCH 1/3] padata: separate serial and parallel cpumasks

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Date:	Fri, 2 Jul 2010 13:34:27 +0400
From:	Dan Kruchinin <dan.kruchinin@...il.com>
To:	Steffen Klassert <steffen.klassert@...unet.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH 1/3] padata: separate serial and parallel cpumasks

On Fri, Jul 2, 2010 at 1:32 PM, Dan Kruchinin <dan.kruchinin@...il.com> wrote:
> On Fri, Jul 2, 2010 at 1:17 PM, Steffen Klassert
> <steffen.klassert@...unet.com> wrote:
>> On Fri, Jul 02, 2010 at 01:07:44PM +0400, Dan Kruchinin wrote:
>>> >
>>> ...
>>
>> But the active cpumask, and now also your serial cpumask might change.
>> We need to catch this changes somehow, that's why I checked the active
>> cpumask against the callback cpu.
>
> You're right, now I get it. Hence the right solution is to check if
> callback CPU is set in serial cpumask every time we do
> padata_do_serial and if it's not, recalculate its value.

padata_do_parallel of course.

> The only thing that embarrasses me in this scheme is the fact that we
> have to allocate cpumask_var_t in pcrypt_do_parallel every time we
> call it then copy serial cpumask into allocated one and then check the
> cb_cpu.
> I think it would be better if we somehow could avoid dynamic cpumask
> allocation. I see the following solutions:
>
> 1) Do the check and cb_cpu value recalculation in padata_do_parallel.
> It may check if cb_cpu is in serial_cpumask and recalculate its value
> if it isn't. The drawback of this scheme is that padata_do_parallel
> now doesn't guaranty it will forward serialization job to the same
> callback CPU we passed to it. If passed CPU is not in serial cpumask
> it will forward serialization to another CPU and we won't know its
> number. The only thing we'll know is that this CPU is in the
> serial_cpumask.
> 2) Create new structure describing pcrypt instance in pcrypt.c which
> will include waitqueue, padata instance and preallocated cpumask which
> will be used for getting padata instance serial cpumsak. It'll help to
> avoid dynamic cpumask allocation but it looks a bit awkward.
>
>>
>> Steffen
>>
>>
>
>
>
> --
> W.B.R.
> Dan Kruchinin
>



-- 
W.B.R.
Dan Kruchinin
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