Re: [RESEND PATCH 1/3] uprobes: Remove redundantlock_page/unlock_page

From: Ingo Molnar
Date: Wed Jun 06 2012 - 05:18:44 EST



* Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> wrote:

> From: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxxxxx>
> ---
> 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);

Is this also a bug fix, or can it wait until v3.6?

Thanks,

Ingo
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