Re: Crash in msm serial on dragonboard with ftrace bootargs

Sai Prakash Ranjan
2018-10-19T14:48:19Z

On 10/19/2018 7:21 PM, Steven Rostedt wrote:
> On Fri, 19 Oct 2018 12:24:05 +0530
> Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> wrote:
>
>>>> Anyone see any problems here?
>>>
>>> This seems sane to me, he says in the other thread that he put 'notrace' to
>>> the msm serial functions (which AIUI should prevent ftrace instrumentation)
>>> and he still sees the issue.
>>>
>>
>> Yes I did add notrace to all functions in msm serial and checked the
>> objdump to make sure that those were not instrumented, and yet the
>> target crashed. This doesnt seem like an issue with ftrace but rather
>> with msm early con.
>
> The thing that still bothers me is that it boots fine without ftrace
> running, and that it requires tracing something to cause the problem.
> This tells me that ftrace has something to do with it. Perhaps it's
> just changing the timing.
>

Yes tracing does cause issue but only if earlycon is present. If I
disable earlycon, then even tracing wont cause any issue and target
boots fine.

> You said that if you add 'ftrace_filter=msm_read' to the command line,
> it still crashes?
>
> So only tracing that function we have an issue, right?
>

Tracing msm_read does cause the crash, but that is not the only one
causing the crash because even after "ftrace_notrace=msm_read" the board
crashes which is why I suspect msm earlycon and not ftrace.

Thanks,
Sai
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