[PATCH] x86: Don't copy per_cpu cpuinfo for BSP two times

[PATCH] x86: Don't copy per_cpu cpuinfo for BSP two times

[Yinghai Lu]

smp_store_cpu_info(0) will do that.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 arch/x86/kernel/smpboot.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Index: linux-2.6/arch/x86/kernel/smpboot.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/smpboot.c
+++ linux-2.6/arch/x86/kernel/smpboot.c
@@ -1071,13 +1071,13 @@ void __init native_smp_prepare_cpus(unsi
 
 	preempt_disable();
 	smp_cpu_index_default();
-	memcpy(__this_cpu_ptr(&cpu_info), &boot_cpu_data, sizeof(cpu_info));
-	cpumask_copy(cpu_callin_mask, cpumask_of(0));
-	mb();
+
 	/*
 	 * Setup boot CPU information
 	 */
 	smp_store_cpu_info(0); /* Final full version of the data */
+	cpumask_copy(cpu_callin_mask, cpumask_of(0));
+	mb();
 #ifdef CONFIG_X86_32
 	boot_cpu_logical_apicid = logical_smp_processor_id();
 #endif

Re: [PATCH] x86: Don't copy per_cpu cpuinfo for BSP two times

[Borislav Petkov]

On Fri, Jan 21, 2011 at 03:29:54PM -0800, Yinghai Lu wrote:
> 
> smp_store_cpu_info(0) will do that.
> 
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> 
> ---
>  arch/x86/kernel/smpboot.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> Index: linux-2.6/arch/x86/kernel/smpboot.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/smpboot.c
> +++ linux-2.6/arch/x86/kernel/smpboot.c
> @@ -1071,13 +1071,13 @@ void __init native_smp_prepare_cpus(unsi
>  
>  	preempt_disable();
>  	smp_cpu_index_default();
> -	memcpy(__this_cpu_ptr(&cpu_info), &boot_cpu_data, sizeof(cpu_info));
> -	cpumask_copy(cpu_callin_mask, cpumask_of(0));
> -	mb();
> +
>  	/*
>  	 * Setup boot CPU information
>  	 */
>  	smp_store_cpu_info(0); /* Final full version of the data */
> +	cpumask_copy(cpu_callin_mask, cpumask_of(0));
> +	mb();

Question: why do we need the memory barrier there? We're running on the
BSP and long before smp_init() to be all careful about the callin_mask.
It could be there as a left over from the 32 and 64-bit merge, AFAICT
from git history...

Thanks.

-- 
Regards/Gruss,
    Boris.

[tip:x86/cpu] x86: Don't copy per_cpu cpuinfo for BSP two times

[tip-bot for Yinghai Lu]

Commit-ID:  792363d2beceb1c7d865e517fa9939c8b8c1442a
Gitweb:     http://git.kernel.org/tip/792363d2beceb1c7d865e517fa9939c8b8c1442a
Author:     Yinghai Lu <yinghai@kernel.org>
AuthorDate: Fri, 21 Jan 2011 15:29:54 -0800
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 26 Jan 2011 08:44:50 +0100

x86: Don't copy per_cpu cpuinfo for BSP two times

smp_store_cpu_info(0) will do that.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
LKML-Reference: <4D3A16F2.5090902@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/kernel/smpboot.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index d396155..a7a3d1a 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1071,13 +1071,13 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
 
 	preempt_disable();
 	smp_cpu_index_default();
-	memcpy(__this_cpu_ptr(&cpu_info), &boot_cpu_data, sizeof(cpu_info));
-	cpumask_copy(cpu_callin_mask, cpumask_of(0));
-	mb();
+
 	/*
 	 * Setup boot CPU information
 	 */
 	smp_store_cpu_info(0); /* Final full version of the data */
+	cpumask_copy(cpu_callin_mask, cpumask_of(0));
+	mb();
 #ifdef CONFIG_X86_32
 	boot_cpu_logical_apicid = logical_smp_processor_id();
 #endif