Re: Crash in msm serial on dragonboard with ftrace bootargs

From: Sai Prakash Ranjan
Date: Fri Oct 19 2018 - 10:48:34 EST

On 10/19/2018 7:21 PM, Steven Rostedt wrote:
On Fri, 19 Oct 2018 12:24:05 +0530
Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx> 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.

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