Re: [patch 7/7] stacktrace filtering for fault-injection capabilities

[Andrew Morton <akpm@osdl.org>]

On Thu, 12 Oct 2006 16:43:12 +0900
Akinobu Mita <akinobu.mita@gmail.com> wrote:

> From: Akinobu Mita <akinobu.mita@gmail.com>
> 
> This patch provides stacktrace filtering feature.
> The stacktrace filter allows failing only for the caller you are
> interested in.
> 
> stacktrace filter is enabled by setting the value of
> /debugfs/*/stacktrace-depth more than 0.
> and specify the range of the virtual address
> by the /debugfs/*/address-start and /debugfs/*/address-end
> 
> Please see the example that demostrates how to inject slab allocation
> failures only for a specific module
> in Documentation/fault-injection/fault-injection.txt

I read the documentation but I still don't understand this feature.  What
does the stacktrace actually do?  It gets stored somewhere and displayed
later?  What's it all for?

> --- work-fault-inject.orig/lib/Kconfig.debug
> +++ work-fault-inject/lib/Kconfig.debug
> @@ -472,6 +472,8 @@ config LKDTM
>  
>  config FAULT_INJECTION
>  	bool
> +	select STACKTRACE
> +	select FRAME_POINTER
>  
>  config FAILSLAB
>  	bool "fault-injection capabilitiy for kmalloc"
> 

Is the selection of FRAME_POINTER really needed?  The fancy new unwinder
is supposed to be able to handle frame-pointerless unwinding?