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    SubjectRe: Crash in msm serial on dragonboard with ftrace bootargs
    On Tue, 16 Oct 2018 22:05:23 +0530
    Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> wrote:

    > On 10/16/2018 8:59 PM, Steven Rostedt wrote:
    > > On Tue, 16 Oct 2018 17:08:25 +0530
    > > Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> wrote:
    > >
    > >> Hi,
    > >>
    > >> On dragonboard 410c, with "ftrace=function" boot args, the console
    > >> output slows down and board resets without any backtrace as below. This
    > >> is tested on latest kernel and seems to exist even in older kernels as well.
    > >
    > > So this only happens when ftrace=function is on the boot console.
    > >
    >
    > Yes. If I do not use boot console, target does not crash.
    >


    > >
    > > Does function tracing work after boot up? That is, without the
    > > ftrace=function, can you do:
    > >
    > > echo function > /sys/kernel/debug/tracing/current_tracer
    > >
    > > without any issue?
    > >
    >
    > Yes ftrace in general works without any issue. I have also tested on
    > db820c and sdm845 where "ftrace=function" works fine. I am seeing this
    > issue only on db410c board.

    OK, can you add to the command line:

    ftrace=function ftrace_filter=*schedule*

    to see if it's a specific function that may be causing the issue (but
    hopefully it's not one of the scheduling functions that caused it).

    >
    > >>
    > >> One more thing is for pstore dmesg-ramoops, I had to change
    > >> late_initcall to postcore_initcall which brings the question as to why
    > >> we changed to late_initcall?
    > >> Simple git blame shows to support crypto compress api, but is it really
    > >> helpful? A lot of boottime issues can be caught with pstore enabled at
    > >> postcore_initcall rather than late_initcall, this backtrace
    > >> is just one example. Is there any way we could change this?
    > >
    > > Does it break if the crypto is not initialized? Perhaps add a command
    > > line flag to have it happen earlier:
    > >
    >
    > I didnt see any breakage, have been using ramoops with postcore_initcall
    > for sometime now.
    >
    > > ramoops=earlyinit
    > >
    > > and add a postcore_initcall that checks if that flag is set, and if so,
    > > it does the work then, and the late_initcall() will do nothing.
    > >
    > > That way, you can still have unmodified kernels use pstore when it
    > > crashes at boot up.
    > >
    >
    > Sounds good.

    Great, I guess you can write a patch to do that ;-)

    -- Steve

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