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From:   Atish Patra <atishp@atishpatra.org>
Date:   Sat, 3 Oct 2020 10:33:07 -0700
Message-ID: <CAOnJCUJgzWkKixYyFCrqbNF2ONgB_RUOSTB9BhT5D0stnf=vUw@mail.gmail.com>
Subject: Re: [Bug 209317] ftrace kernel self test failure on RISC-V on 5.8,
 regression from 5.4.0
To:     Alan Kao <alankao@andestech.com>, Zong Li <zong.li@sifive.com>
Cc:     "rostedt@goodmis.org" <rostedt@goodmis.org>,
        "aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
        "bugzilla-daemon@bugzilla.kernel.org" 
        <bugzilla-daemon@bugzilla.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "palmer@dabbelt.com" <palmer@dabbelt.com>,
        "paul.walmsley@sifive.com" <paul.walmsley@sifive.com>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        Atish Patra <Atish.Patra@wdc.com>
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Hi Alan and Zong,
I initially suspected ftrace is broken between v5.6 & v5.7 as Kolin pointed out.
I couldn't find any reason how the HSM patch is related. Zong's ftrace
patching code was also merged in that release.
However, I was able to reproduce the issue in the older kernel(v5.4)
as well on both Qemu & Unleashed hardware.
Here are the steps:

mount -t debugfs none /sys/kernel/debug/
cd /sys/kernel/debug/tracing
echo function_graph > current_tracer
echo function > current_tracer

It works for the first time with function_graph but writing any other
tracer crashes immediately.
Can you take a look to check if the bug is in ftrace infrastructure code ?

On Mon, Sep 28, 2020 at 10:25 AM Atish Patra <Atish.Patra@wdc.com> wrote:
>
> On Mon, 2020-09-28 at 11:13 -0400, Steven Rostedt wrote:
> > On Sat, 26 Sep 2020 22:02:35 +0000
> > bugzilla-daemon@bugzilla.kernel.org wrote:
> >
> > > https://bugzilla.kernel.org/show_bug.cgi?id=209317
> > >
> > > --- Comment #4 from Colin Ian King (colin.king@canonical.com) ---
> > > Issue still in 5.9-rc6
> > >
> >
> > Atish,
> >
> > As the issues bisects down to your commit, care to take a look at
> > this.
> > (And take ownership of this bug)
> >
>
> Yes. I am already looking into this. Colin informed me about the bug
> over the weekend.
>
> I couldn't change the ownership as I am not part of the editbugs group.
> I have sent an email to helpdesk@kernel.org for access.
>
> > -- Steve
>
> --
> Regards,
> Atish
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv


-- 
Regards,
Atish