linux-kernel - Re: [PATCH 3/7] percpu: clean up percpu variable definitions

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Date:	Mon, 01 Jun 2009 02:40:06 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	tj@...nel.org
Cc:	JBeulich@...ell.com, andi@...stfloor.org, mingo@...e.hu,
	hpa@...or.com, tglx@...utronix.de, linux-kernel@...r.kernel.org,
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	chris@...kel.net, rusty@...tcorp.com.au, jens.axboe@...cle.com,
	davej@...hat.com, jeremy@...source.com, linux-mm@...ck.org
Subject: Re: [PATCH 3/7] percpu: clean up percpu variable definitions

From: Tejun Heo <tj@...nel.org>
Date: Mon,  1 Jun 2009 17:58:24 +0900

> --- a/arch/cris/include/asm/mmu_context.h
> +++ b/arch/cris/include/asm/mmu_context.h
> @@ -17,7 +17,7 @@ extern void switch_mm(struct mm_struct *prev, struct mm_struct *next,
>   * registers like cr3 on the i386
>   */
>  
> -extern volatile DEFINE_PER_CPU(pgd_t *,current_pgd); /* defined in arch/cris/mm/fault.c */
> +DECLARE_PER_CPU(pgd_t *,current_pgd); /* defined in arch/cris/mm/fault.c */
>  
>  static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
>  {

Yes volatile sucks, but might this break something?

Whether the volatile is actually needed or not, it's bad to have this
kind of potential behavior changing nugget hidden in this seemingly
inocuous change.  Especially if you're the poor soul who ends up
having to debug it :-/
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