lkml.org 
[lkml]   [2017]   [Nov]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [vlan_device_event] BUG: unable to handle kernel paging request at 6b6b6ccf
On Wed, Nov 8, 2017 at 9:12 AM, Fengguang Wu <fengguang.wu@intel.com> wrote:
>
> OK. Here is the original faddr2line output:
>
> $ ~/linux/scripts/faddr2line vmlinux vlan_device_event+0x7f5/0xa40
> vlan_device_event+0x7f5/0xa40:
> vlan_device_event at net/8021q/vlan.h:60

Hmm. Yes, that's not what I hoped for.

> I notice that this trace shows no additional inline files at all.
> Is it because I did some kconfig option wrong, so that inline info is
> lost? Eg.
>
> CONFIG_OPTIMIZE_INLINING=y (reading lib/Kconfig.debug, it looks better set to N)
> CONFIG_DEBUG_INFO_REDUCED=y
> CONFIG_DEBUG_INFO_SPLIT=y

Hmm. It might also be a compiler/linker issue. Debug info is sadly
often a second class citizen, because it's generally not something
that gets tested nearly as much as the actual _code_ that a compiler
generates.

So we've certainly had issues before with incomplete debug info.

That said, I'm not sure how well that CONFIG_DEBUG_INFO_SPLIT works,
I've only ever tested with

CONFIG_DEBUG_INFO=y
CONFIG_DEBUG_INFO_REDUCED=y
# CONFIG_DEBUG_INFO_SPLIT is not set
# CONFIG_DEBUG_INFO_DWARF4 is not set

which was the config that my scheduler example was generated from.

It might be an issue with the particular version of 'addr2line' too,
for all I know. The one I have is

GNU addr2line version 2.27-24.fc26

and who knows what else could influence it. I *thought* that as long
as you just had DEBUG_INFO enabled, it would automatically be ok, but
I was clearly wrong.

> [ 745.719623] BUG: unable to handle kernel paging request at 6b6b6f4f
> [ 745.732871] IP: vlan_device_event+0x7f5/0xa40:
> vlan_device_event at net/8021q/vlan.h:60

Ok, at least now there's no lost information, even if it doesn't have
that nice inlining information that I was hoping for.

Linus

\
 
 \ /
  Last update: 2017-11-08 21:14    [W:0.099 / U:2.500 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site