linux-kernel - Re: [PATCH] x86, tlb: small cleanup for native_flush_tlb

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Date:	Tue, 15 Mar 2011 09:57:37 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	hpa@...or.com, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86, tlb: small cleanup for native_flush_tlb_others

On 03/14/2011 08:33 PM, Ingo Molnar wrote:
> 
> * Xiao Guangrong <xiaoguangrong@...fujitsu.com> wrote:
> 
>> Use smp_processor_id instead of get_cpu and put_cpu since
>> the caller has already disabled preemption
>>
>> Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
>> ---
>>  arch/x86/mm/tlb.c |    3 +--
>>  1 files changed, 1 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
>> index 6acc724..92849d0 100644
>> --- a/arch/x86/mm/tlb.c
>> +++ b/arch/x86/mm/tlb.c
>> @@ -211,11 +211,10 @@ void native_flush_tlb_others(const struct cpumask *cpumask,
>>  	if (is_uv_system()) {
>>  		unsigned int cpu;
>>  
>> -		cpu = get_cpu();
>> +		cpu = smp_processor_id();
>>  		cpumask = uv_flush_tlb_others(cpumask, mm, va, cpu);
>>  		if (cpumask)
>>  			flush_tlb_others_ipi(cpumask, mm, va);
>> -		put_cpu();
>>  		return;
> 
> There's multiple callers. Could you please update the changelog with the list of 
> callers and a statement that all of them disable preemption already?
> 

Thanks Ingo, there is the new version.

From: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Subject: [PATCH] x86, tlb: small micro-optimization for native_flush_tlb_others

native_flush_tlb_others is called from:
flush_tlb_current_task
flush_tlb_mm
flush_tlb_page

All these functions disable preemption explicitly, so we can use smp_processor_id
instead of get_cpu and put_cpu

Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
---
 arch/x86/mm/tlb.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 6acc724..92849d0 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -211,11 +211,10 @@ void native_flush_tlb_others(const struct cpumask *cpumask,
 	if (is_uv_system()) {
 		unsigned int cpu;
 
-		cpu = get_cpu();
+		cpu = smp_processor_id();
 		cpumask = uv_flush_tlb_others(cpumask, mm, va, cpu);
 		if (cpumask)
 			flush_tlb_others_ipi(cpumask, mm, va);
-		put_cpu();
 		return;
 	}
 	flush_tlb_others_ipi(cpumask, mm, va);
-- 
1.7.4

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