linux-kernel - Re: [tip:x86/cleanups] x86, dumpstack: Use frame pointer during stack trace

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Message-ID: <20110310230222.GB1837@nowhere>
Date:	Fri, 11 Mar 2011 00:02:23 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, namhyung@...il.com
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/cleanups] x86, dumpstack: Use frame pointer during
 stack trace

On Thu, Mar 10, 2011 at 10:26:07PM +0000, tip-bot for Namhyung Kim wrote:
> Commit-ID:  2f8058ae197236f9d5641850ce27f67d8f3e0b39
> Gitweb:     http://git.kernel.org/tip/2f8058ae197236f9d5641850ce27f67d8f3e0b39
> Author:     Namhyung Kim <namhyung@...il.com>
> AuthorDate: Tue, 8 Mar 2011 20:44:22 +0900
> Committer:  Thomas Gleixner <tglx@...utronix.de>
> CommitDate: Thu, 10 Mar 2011 23:20:30 +0100
> 
> x86, dumpstack: Use frame pointer during stack trace
> 
> If CONFIG_FRAME_POINTER is set then use the frame pointer for the
> stack backtrace rather than scanning whole stack blindly.

We don't do it blindly, we actually check the reliability with the
frame pointer.

I'm not sure this patch is a good idea. stack dumps need to stay very
robust and not exclusively rely on the frame pointer to be correct.
At least walking blindly the stack provides a best effort dump as a last
resort.


> 
> Signed-off-by: Namhyung Kim <namhyung@...il.com>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> LKML-Reference: <1299584662-24421-4-git-send-email-namhyung@...il.com>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/kernel/dumpstack.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
> index 38b74a5e..56db27d 100644
> --- a/arch/x86/kernel/dumpstack.c
> +++ b/arch/x86/kernel/dumpstack.c
> @@ -170,7 +170,11 @@ static const struct stacktrace_ops print_trace_ops = {
>  	.warning_symbol		= print_trace_warning_symbol,
>  	.stack			= print_trace_stack,
>  	.address		= print_trace_address,
> +#ifdef CONFIG_FRAME_POINTER
> +	.walk_stack		= walk_context_stack_bp,
> +#else
>  	.walk_stack		= walk_context_stack,
> +#endif
>  };
--
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