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Re: [HELP] ubacktrace() problem
- From: Jinhua Luo <luajit dot io at gmail dot com>
- To: "Frank Ch. Eigler" <fche at redhat dot com>
- Cc: systemtap at sourceware dot org
- Date: Thu, 14 Jan 2016 11:40:19 +0800
- Subject: Re: [HELP] ubacktrace() problem
- Authentication-results: sourceware.org; auth=none
- References: <CAAc9rOzFmkSKJCmi=0=Vggvaf3-VnwgfHFPfBxG475NKso3arQ at mail dot gmail dot com> <y0m7fje98cy dot fsf at fche dot csb> <CAAc9rOxJNeVvyjeRX==GpNU9H=Sh+AfFUgLtLPqxFpWJnj_K3w at mail dot gmail dot com> <20160113152312 dot GC7497 at redhat dot com>
Hi,
I reported the issue to debian-kernel mailing list:
https://lists.debian.org/debian-kernel/2016/01/msg00266.html
I recompile the kernel, include the vdso files, now I could see the
backtrace, but it's not complete.
It lacks of main, __libc_start_main, _start.
And some functions should not be the first entry in the backtrace.
The correct graph on Ubuntu 14.04:
http://luajit.io/systemtap/pgsql/postgres_1.svg
The wrong graph on Debian8:
http://luajit.io//systemtap/pgsql/postgres_wrong.svg
Maybe the glibc and its debuginfo on Debian8 is bad?
Regards,
Jinhua Luo
2016-01-13 23:23 GMT+08:00 Frank Ch. Eigler <fche@redhat.com>:
> Hi -
>
>> > % rpm -ql kernel-debuginfo | grep vdso
>> > /usr/lib/debug/lib/modules/4.2.6-200.fc22.x86_64/vdso
>> > [...]
>> > These may be necessary to be able to unwind through the kernel-user
>> > transition [...]
>>
>> Thanks for the information! The debian indeed lacks of vdso files in
>> the kernel package.
>
> Please let us know when/if a debian bug is opened, so we can track it.
>
>
>> [...] I am still wondering if the warnings denotes that the
>> collected backtraces are not so accurate and complete.
>
> Well, they will be as accurate and complete as systemtap can make it,
> with the imperfect data it is given. Use the warnings to help (us)
> diagnose known problem cases, otherwise please don't worry about them.
>
>
> - FChE