linux-kernel - Re: x86/kconfig: Consolidate unwinders into multiple choice selection

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Date:   Tue, 5 Sep 2017 13:09:53 -0400
From:   Dave Jones <davej@...emonkey.org.uk>
To:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: x86/kconfig: Consolidate unwinders into multiple choice selection

On Mon, Sep 04, 2017 at 08:05:13PM +0000, Linux Kernel wrote:
 > Web:        https://git.kernel.org/torvalds/c/81d387190039c14edac8de2b3ec789beb899afd9
 > Commit:     81d387190039c14edac8de2b3ec789beb899afd9
 > Parent:     a34a766ff96d9e88572e35a45066279e40a85d84
 > Refname:    refs/heads/master
 > Author:     Josh Poimboeuf <jpoimboe@...hat.com>
 > AuthorDate: Tue Jul 25 08:54:24 2017 -0500
 > Committer:  Ingo Molnar <mingo@...nel.org>
 > CommitDate: Wed Jul 26 14:05:36 2017 +0200
 > 
 >     x86/kconfig: Consolidate unwinders into multiple choice selection
 >     
 >     There are three mutually exclusive unwinders.  Make that more obvious by
 >     combining them into a multiple-choice selection:
 >     
 >       CONFIG_FRAME_POINTER_UNWINDER
 >       CONFIG_ORC_UNWINDER
 >       CONFIG_GUESS_UNWINDER (if CONFIG_EXPERT=y)

The help texts for the various unwinders are now attached to the wrong
kconfig item.

 > +choice
 > +	prompt "Choose kernel unwinder"
 > +	default FRAME_POINTER_UNWINDER
 > +	---help---
 > +	  This determines which method will be used for unwinding kernel stack
 > +	  traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
 > +	  livepatch, lockdep, and more.

This is what gets displayed, but tells me nothing about what the
benefits/downsides are of each (or even what they are; I had to read the
Kconfig file to figure out what 'GUESS' meant)


an oldconfig run ..


Choose kernel unwinder
> 1. Frame pointer unwinder (FRAME_POINTER_UNWINDER) (NEW)
  2. ORC unwinder (ORC_UNWINDER) (NEW)
  3. Guess unwinder (GUESS_UNWINDER) (NEW)
choice[1-3?]: ?

This determines which method will be used for unwinding kernel stack
traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
livepatch, lockdep, and more.

Prompt: Choose kernel unwinder
  Location:
    -> Kernel hacking
  Defined at arch/x86/Kconfig.debug:359
  Selected by: m



Choose kernel unwinder
> 1. Frame pointer unwinder (FRAME_POINTER_UNWINDER) (NEW)
  2. ORC unwinder (ORC_UNWINDER) (NEW)
  3. Guess unwinder (GUESS_UNWINDER) (NEW)
choice[1-3?]: 



	Dave