linux-kernel - Re: [PATCH v2] cpumask: add cpumask_var

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Date:	Thu, 28 Apr 2011 12:33:50 -0300
From:	Thiago Farina <tfransosi@...il.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2] cpumask: add cpumask_var_t documentation

On Thu, Apr 28, 2011 at 12:27 PM, KOSAKI Motohiro
<kosaki.motohiro@...fujitsu.com> wrote:
> cpumask_var_t has one nortable difference against cpumask_t.
> This patch adds the explanation.
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> ---
>  include/linux/cpumask.h |   14 ++++++++++++++
>  1 files changed, 14 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index 1e40dd0..471c98a 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -617,6 +617,20 @@ static inline size_t cpumask_size(void)
>  *       ... use 'tmpmask' like a normal struct cpumask * ...
>  *
>  *     free_cpumask_var(tmpmask);
> + *
> + *
> + * However, one notable exception is there. cpumask_var_t is allocated
> + * only nr_cpu_ids bits

Maybe, instead of "is allocated only", "allocates only" ?


> (in the other hand, real cpumask_t always has
> + * NR_CPUS bits). therefore You don't have to dereference cpumask_var_t.

s/therefore You/Therefore you/ ?

> + *
> + *     cpumask_var_t tmpmask;
> + *     if (!alloc_cpumask_var(&tmpmask, GFP_KERNEL))
> + *             return -ENOMEM;
> + *
> + *     var = *tmpmask;
> + *
> + * This code makes NR_CPUS length memcopy and bring memroy corruption.

/s/memroy/memory

You are saying that I should not use this code? I'm confused, could
you explain a little bit?

> + * You have to use cpumask_copy() instead.
>  */

I don't get this. :(


>  #ifdef CONFIG_CPUMASK_OFFSTACK
>  typedef struct cpumask *cpumask_var_t;
> --
> 1.7.3.1
>
>
>
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