linux-kernel - Re: [PATCH 0/6] Tracing register accesses with pstore and dynamic debug

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Message-ID: <15ec736d-bd54-5519-4b99-47dd161bc556@codeaurora.org>
Date:   Sun, 21 Oct 2018 09:16:59 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Laura Abbott <labbott@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Anton Vorontsov <anton@...msg.org>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        Colin Cross <ccross@...roid.com>,
        Jason Baron <jbaron@...mai.com>,
        Tony Luck <tony.luck@...el.com>, Arnd Bergmann <arnd@...db.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Joe Perches <joe@...ches.com>,
        Jim Cromie <jim.cromie@...il.com>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Sibi Sankar <sibis@...eaurora.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Prasad Sodagudi <psodagud@...eaurora.org>,
        tsoni@...eaurora.org, Bryan Huntsman <bryanh@...eaurora.org>,
        Tingwei Zhang <tingwei@...eaurora.org>, tkjos@...gle.com
Subject: Re: [PATCH 0/6] Tracing register accesses with pstore and dynamic
 debug

On 10/20/2018 9:57 PM, Joel Fernandes wrote:
> On Sat, Oct 20, 2018 at 12:02:37PM +0530, Sai Prakash Ranjan wrote:
>> On 10/20/2018 10:55 AM, Joel Fernandes wrote:
>>> On Sun, Sep 09, 2018 at 01:57:01AM +0530, Sai Prakash Ranjan wrote:
>>>> Hi,
>>>>
>>>> This patch series adds Event tracing support to pstore and is continuation
>>>> to the RFC patch introduced to add a new tracing facility for register
>>>> accesses called Register Trace Buffer(RTB). Since we decided to not introduce
>>>> a separate framework to trace register accesses and use existing framework
>>>> like tracepoints, I have moved from RFC. Details of the RFC in link below:
>>>>
>>>> Link: https://lore.kernel.org/lkml/cover.1535119710.git.saiprakash.ranjan@codeaurora.org/
>>>>
>>>> MSR tracing example given by Steven was helpful in using tracepoints for
>>>> register accesses instead of using separate trace. But just having these
>>>> IO traces would not help much unless we could have them in some persistent
>>>> ram buffer for debugging unclocked access or some kind of bus hang or an
>>>> unexpected reset caused by some buggy driver which happens a lot during
>>>> initial development stages. By analyzing the last few entries of this buffer,
>>>> we could identify the register access which is causing the issue.
>>>
>>> Hi Sai,
>>>
>>> I wanted to see if I could make some time to get your patches working. We are
>>> hitting usecases that need something like this as well. Basically devices
>>> hanging and then the ramdump does not tell us much, so in this case pstore
>>> events can be really helpful. This usecase came up last year as well.
>>>
>>> Anyway while I was going through your patches, I cleaned up some pstore code
>>> as well and I have 3 more patches on top of yours for this clean up. I prefer
>>> we submit the patches together and sync our work together so that there is
>>> least conflict.
>>>
>>> Here's my latest tree:
>>> https://github.com/joelagnel/linux-kernel/commits/pstore-events
>>> (note that I have only build tested the patches since I just wrote them and
>>> its quite late in the night here ;-))
>>>
>>
>> Hi Joel,
>>
>> Thanks for looking into this. Sure, I will be happy to sync up with you on
> 
> Thanks. And added a fourth patch in the tree too.
> 
>> this. I can test your additional patches on top of my pstore patches. BTW,
>> I'm still stuck at copying binary record into pstore and then extract it
>> during read time. Seems like I'm missing something.
> 
> Sure, push your latest somewhere and let me know. I'll try to get you unstuck.
> 

Thanks Joel, I will push my changes and let you know in some time.

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