linux-kernel - Re: [RESEND PATCH 1/3] uprobes: Remove redundant lock_page/unlock

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Message-ID: <1344254271.19356.8.camel@bandura>
Date:	Mon, 06 Aug 2012 13:57:51 +0200
From:	Anton Arapov <anton@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Subject: Re: [RESEND PATCH 1/3] uprobes: Remove redundant
 lock_page/unlock_page

Ingo,

  just a "ping" message, so that this change won't be forgotten.
  It was waiting for v3.6: https://lkml.org/lkml/2012/6/6/134

thank you!
Anton.

On Fri, 2012-06-01 at 14:49 +0530, Srikar Dronamraju wrote:
> From: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> 
> Since read_opcode() reads from the referenced page and doesnt modify
> the page contents nor the page attributes, there is no need to lock
> the page.
> 
> Signed-off-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> ---
>  Modified changelog based on comments from Peter Zijlstra
> 
>  kernel/events/uprobes.c |    2 --
>  1 files changed, 0 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 42b21eb..b3f3095 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -315,12 +315,10 @@ static int read_opcode(struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_
>  	if (ret <= 0)
>  		return ret;
>  
> -	lock_page(page);
>  	vaddr_new = kmap_atomic(page);
>  	vaddr &= ~PAGE_MASK;
>  	memcpy(opcode, vaddr_new + vaddr, UPROBE_SWBP_INSN_SIZE);
>  	kunmap_atomic(vaddr_new);
> -	unlock_page(page);
>  
>  	put_page(page);
>  
> 
> --
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