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    SubjectRe: [Bug 209317] ftrace kernel self test failure on RISC-V on 5.8, regression from 5.4.0
    On Sun, Oct 4, 2020 at 11:08 PM Zong Li <zong.li@sifive.com> wrote:
    >
    > Hi Atish,
    >
    > I can take out some time to take a look at it together, if anyone here
    > fixes it or has ideas, please share the information, thanks.
    >

    Thanks. I observed this in case it helps.

    Across kernels, the panic trace seems to point out the one of the
    first two functions after patching is corrupted.
    rcu_momentary_dyntick_idle or stop_machine_yield[1]

    [1]https://elixir.bootlin.com/linux/v5.9-rc7/source/kernel/stop_machine.c#L213

    I am suspecting nop was not replaced with the correct auipc+jalr pair?

    > On Sun, Oct 4, 2020 at 1:33 AM Atish Patra <atishp@atishpatra.org> wrote:
    > >
    > > 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



    --
    Regards,
    Atish

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