linux-kernel - Re: [PATCH 1/7] x86: don't show trace beyond show

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Date:	Mon, 8 Apr 2013 18:08:11 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, mingo@...hat.com, x86@...nel.org,
	rth@...ddle.net, linux@....linux.org.uk, msalter@...hat.com,
	starvik@...s.com, dhowells@...hat.com, tony.luck@...el.com,
	benh@...nel.crashing.org, takata@...ux-m32r.org,
	geert@...ux-m68k.org, james.hogan@...tec.com, monstr@...str.eu,
	ralf@...ux-mips.org, jonas@...thpole.se, rkuo@...eaurora.org,
	schwidefsky@...ibm.com, liqin.chen@...plusct.com,
	davem@...emloft.net, lethal@...ux-sh.org, vgupta@...opsys.com,
	chris@...kel.net, cmetcalf@...era.com, ysato@...rs.sourceforge.jp,
	gxt@...c.pku.edu.cn, jdike@...toit.com
Subject: Re: [PATCH 1/7] x86: don't show trace beyond show_stack(NULL, NULL)


* Tejun Heo <tj@...nel.org> wrote:

> show_stack(current or NULL, NULL) is used to print the backtrace of
> the current task.  As trace beyond the function itself isn't of much
> interest to anyone, don't show it by determining sp and bp in
> show_stack()'s frame and passing them to show_stack_log_lvl().
> 
> This brings show_stack(NULL, NULL)'s behavior in line with
> dump_stack().
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> ---
>  arch/x86/kernel/dumpstack.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
> index c8797d5..dd1a7c3 100644
> --- a/arch/x86/kernel/dumpstack.c
> +++ b/arch/x86/kernel/dumpstack.c
> @@ -176,7 +176,19 @@ void show_trace(struct task_struct *task, struct pt_regs *regs,
>  
>  void show_stack(struct task_struct *task, unsigned long *sp)
>  {
> -	show_stack_log_lvl(task, NULL, sp, 0, "");
> +	unsigned long bp = 0;
> +	unsigned long stack;
> +
> +	/*
> +	 * Stack frames below this one aren't interesting.  Don't show them
> +	 * if we're printing for %current.
> +	 */
> +	if (!sp && (!task || task == current)) {
> +		sp = &stack;
> +		bp = stack_frame(current, NULL);
> +	}
> +
> +	show_stack_log_lvl(task, NULL, sp, bp, "");

Hm, show_regs() has a similar problem AFAICS.

Would be nice to create an __always_inline helper for all this, and to use it for 
show_regs() as well.

Then the !bp special case in dump_trace() could be removed, and !bp be made an 
invalid variant.

Thanks,

	Ingo
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