linux-kernel - Re: Bug with jprobes and function graph tracer

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Date:	Tue, 13 Jan 2015 21:46:33 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, vvs@...ru
Subject: Re: Bug with jprobes and function graph tracer

(2015/01/13 21:22), Steven Rostedt wrote:
> On Tue, 13 Jan 2015 20:39:33 +0900
> Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:
> 
>>
>> Yeah we should try to fix this, but not so high priority since jprobe
>> is not used so frequently. I guess one easy solution is adding notrace
>> to all jprobe handlers for hiding it from function-graph tracer.
>> If there is a way to check a function is notrace or not, I can use that
>> in register_jprobe and reject it if the handler is not "notrace"ed. :)
> 
> Adding notrace should be the last resort. Every notrace in the kernel
> makes function tracing a little more useless. It bothers me even more
> when notrace is added because of function graph tracing but the
> function still works for function tracing.

I see.

> 
> I worked on this for the last few days and have a patch that fixes the
> problem. I'll be posting it later today. It also uncovered another
> unrelated bug that I worked on yesterday, otherwise I would have posted
> these fixes already.

Great! I look forward that! :)

> 
> I have a fix for the other bug now but it needs to be cleaned up
> (remove all the debugging prints from it). When that's complete I'll
> post the patches and get them ready for mainline and stable.

Thank you,

> 
> Thanks,
> 
> -- Steve
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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