linux-kernel - Re: [PATCH v3] cpumask: add cpumask_var

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Message-ID: <BANLkTiktDSC=njLhJZF9EVWEqBPWa=K7Ow@mail.gmail.com>
Date:	Thu, 28 Apr 2011 12:48:58 -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 v3] cpumask: add cpumask_var_t documentation

On Thu, Apr 28, 2011 at 12:43 PM, KOSAKI Motohiro
<kosaki.motohiro@...fujitsu.com> wrote:
>> 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" ?
>
> Instead, "alloc_cpumask_var() allocates only nr_cpu_ids bits" is more clear? :)
>
Yup. Thx.

>
>> > (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/ ?
>>
>
> Thx.
>
>
>> > + *
>> > + *     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?
>
> Yes. you aren't confused.
>
>
>> > + * You have to use cpumask_copy() instead.
>> >  */
>>
>> I don't get this. :(
>
> "cpumask_copy() privide safe copy functionality." is clear?
>
Yes. ;)

>
> From d2ea9d4846e46bcc8a82b9a641ede3a10aca346c Mon Sep 17 00:00:00 2001
> From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Date: Tue, 26 Apr 2011 19:58:39 +0900
> Subject: [PATCH v3] cpumask: add cpumask_var_t documentation
>
> 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..e2b9032 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. alloc_cpumask_var() allocates
> + * only nr_cpumask_bits bits (in the other hand, real cpumask_t always has
> + * NR_CPUS bits). Therefore you don't have to dereference cpumask_var_t.
> + *
> + *     cpumask_var_t tmpmask;
> + *     if (!alloc_cpumask_var(&tmpmask, GFP_KERNEL))
> + *             return -ENOMEM;
> + *
> + *     var = *tmpmask;
> + *
> + * This code makes NR_CPUS length memcopy and bring memory corruption.

Maybe:

s/bring memory/brings to a memory/

?

> + * cpumask_copy() privide safe copy functionality.
s/privide/provides ?

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