linux-kernel - Re: [PATCH v3 0/7] arm64: ftrace: fix incorrect output from stack tracer

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Date:	Thu, 22 Oct 2015 23:05:43 +0900
From:	Jungseok Lee <jungseoklee85@...il.com>
To:	AKASHI Takahiro <takahiro.akashi@...aro.org>
Cc:	catalin.marinas@....com, will.deacon@....com, rostedt@...dmis.org,
	olof@...om.net, broonie@...nel.org, david.griego@...aro.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/7] arm64: ftrace: fix incorrect output from stack tracer

On Oct 8, 2015, at 11:45 PM, Jungseok Lee wrote:
> On Oct 8, 2015, at 7:01 PM, AKASHI Takahiro wrote:
> 
> Hi Akashi,
> 
>> This is the third patch series for fixing stack tracer on arm64.
>> The original issue was reported by Jungseok[1], and then I found more
>> issues[2].
>> (Steven, Jungseok, sorry for not replying to your comments directly.)
>> 
>> I address here all the issues and implement fixes described in [2] except
>> for interrupt-triggered problems, ie. II-3). Recent discussions[3] about
>> introducing a dedicated interrupt stack suggests that we may avoid walking
>> through from an interrupt stack to a process stack.
>> (So interrupt-stack patch is a prerequisite.)
>> 
>> Basically,
>> patch1 corresponds to the original issue.
>> patch2 is a proactive improvement of function_graph tracer. 
>> patch3 corresponds to II-4(functions under function_graph tracer).
>> patch4 corresponds to II-5(leaf function).
>> patch5, 6 and 7 correspond to II-1(slurping stack) and II-2(differences
>> between x86 and arm64).
>> 
>> Each fix can be applied independently, but if patch5, 6 and 7 are
>> acceptable, patch1 is not necessary because patch7 replaces a default
>> stack tracer.

I've used this series *without Patch1* for over a week.

It works well till now. I have not observed any issues, such as function graph
thing, of which I'm aware. Please note that I have not reviewed internals of
the analyzer and related logics carefully.

Best Regards
Jungseok Lee

>> I tested the code with v4.3-rc3 + Jungseok's patch v3[4].
>> 
>> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/354126.html
>> [2] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/355920.html 
>> [3] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-September/368003.html
>> [4] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-September/371451.html
> 
> The [4] is not a valid patch. I hope the test has been going with the following one.
> 
> 	http://www.kernelhub.org/?msg=841034&p=2
> 
> I will leave comments after playing with this series on top of my IRQ stack tree.
> 
> Best Regards
> Jungseok Lee

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