Re: [PATCH] x86: remove the useless branch in c_start()

Re: [PATCH] x86: remove the useless branch in c_start()

[Michael Wang]

On 09/19/2012 01:42 PM, Michael Wang wrote:
> Since 'cpu == -1' in cpumask_next() is legal, no need to handle '*pos == 0'
> specially.
> 
> About the comments:
> 	/* just in case, cpu 0 is not the first */
> A test with a cpumask in which cpu 0 is not the first has been done, and it
> works well.

Could I get some comments on this patch?

Regards,
Michael Wang

> 
> This patch will remove that useless branch to clean the code.
> 
> Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
> ---
>  arch/x86/kernel/cpu/proc.c |    5 +----
>  1 files changed, 1 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
> index 8022c66..fbd8955 100644
> --- a/arch/x86/kernel/cpu/proc.c
> +++ b/arch/x86/kernel/cpu/proc.c
> @@ -140,10 +140,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
> 
>  static void *c_start(struct seq_file *m, loff_t *pos)
>  {
> -	if (*pos == 0)	/* just in case, cpu 0 is not the first */
> -		*pos = cpumask_first(cpu_online_mask);
> -	else
> -		*pos = cpumask_next(*pos - 1, cpu_online_mask);
> +	*pos = cpumask_next(*pos - 1, cpu_online_mask);
>  	if ((*pos) < nr_cpu_ids)
>  		return &cpu_data(*pos);
>  	return NULL;
> 

Re: [PATCH] x86: remove the useless branch in c_start()

[Borislav Petkov]

On Wed, Sep 26, 2012 at 11:43:52AM +0800, Michael Wang wrote:
> On 09/19/2012 01:42 PM, Michael Wang wrote:
> > Since 'cpu == -1' in cpumask_next() is legal, no need to handle '*pos == 0'
> > specially.
> > 
> > About the comments:
> > 	/* just in case, cpu 0 is not the first */
> > A test with a cpumask in which cpu 0 is not the first has been done, and it
> > works well.
> 
> Could I get some comments on this patch?

Looks ok to me:

Acked-by: Borislav Petkov <borislav.petkov@amd.com>

Thanks.

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
GM: Alberto Bozzo
Reg: Dornach, Landkreis Muenchen
HRB Nr. 43632 WEEE Registernr: 129 19551

Re: [PATCH] x86: remove the useless branch in c_start()

[Michael Wang]

On 09/26/2012 09:02 PM, Borislav Petkov wrote:
> On Wed, Sep 26, 2012 at 11:43:52AM +0800, Michael Wang wrote:
>> On 09/19/2012 01:42 PM, Michael Wang wrote:
>>> Since 'cpu == -1' in cpumask_next() is legal, no need to handle '*pos == 0'
>>> specially.
>>>
>>> About the comments:
>>> 	/* just in case, cpu 0 is not the first */
>>> A test with a cpumask in which cpu 0 is not the first has been done, and it
>>> works well.
>>
>> Could I get some comments on this patch?
> 
> Looks ok to me:
> 
> Acked-by: Borislav Petkov <borislav.petkov@amd.com>
> 
> Thanks.

Thanks for your review.

Regards,
Michael Wang
> 

[tip:x86/cpu] x86: Remove the useless branch in c_start()

[tip-bot for Michael Wang]

Commit-ID:  dec08a837fda146fee498ffc5ecd0d2eeeacd025
Gitweb:     http://git.kernel.org/tip/dec08a837fda146fee498ffc5ecd0d2eeeacd025
Author:     Michael Wang <wangyun@linux.vnet.ibm.com>
AuthorDate: Wed, 19 Sep 2012 13:42:23 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 26 Sep 2012 13:27:56 +0200

x86: Remove the useless branch in c_start()

Since 'cpu == -1' in cpumask_next() is legal, no need to handle
'*pos == 0' specially.

About the comments:

	/* just in case, cpu 0 is not the first */

A test with a cpumask in which cpu 0 is not the first has been
done, and it works well.

This patch will remove that useless branch to clean the code.

Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Cc: kjwinchester@gmail.com
Cc: borislav.petkov@amd.com
Cc: ak@linux.intel.com
Link: http://lkml.kernel.org/r/1348033343-23658-1-git-send-email-wangyun@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/cpu/proc.c |    5 +----
 1 files changed, 1 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index 8022c66..fbd8955 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -140,10 +140,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 
 static void *c_start(struct seq_file *m, loff_t *pos)
 {
-	if (*pos == 0)	/* just in case, cpu 0 is not the first */
-		*pos = cpumask_first(cpu_online_mask);
-	else
-		*pos = cpumask_next(*pos - 1, cpu_online_mask);
+	*pos = cpumask_next(*pos - 1, cpu_online_mask);
 	if ((*pos) < nr_cpu_ids)
 		return &cpu_data(*pos);
 	return NULL;