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From:   Florent Revest <revest@chromium.org>
Date:   Mon, 20 Mar 2023 18:45:08 +0100
Message-ID: <CABRcYmL_JCAGSoX98dZUhGkmek+5iL4kd+F_POJ65GfnZLADcg@mail.gmail.com>
Subject: Re: [PATCH 5/7] ftrace: Store direct called addresses in their ops
To:     Jiri Olsa <olsajiri@gmail.com>
Cc:     Steven Rostedt <rostedt@goodmis.org>, linux-kernel@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org, mhiramat@kernel.org,
        mark.rutland@arm.com, ast@kernel.org, daniel@iogearbox.net,
        kpsingh@kernel.org
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On Sun, Mar 19, 2023 at 7:55=E2=80=AFPM Jiri Olsa <olsajiri@gmail.com> wrot=
e:
>
> On Sun, Mar 19, 2023 at 01:54:43PM -0400, Steven Rostedt wrote:
> > On Sun, 19 Mar 2023 16:29:22 +0100
> > Jiri Olsa <olsajiri@gmail.com> wrote:
> >
> > > > +++ b/kernel/trace/ftrace.c
> > > > @@ -2582,9 +2582,8 @@ ftrace_add_rec_direct(unsigned long ip, unsig=
ned long addr,
> > > >  static void call_direct_funcs(unsigned long ip, unsigned long pip,
> > > >                         struct ftrace_ops *ops, struct ftrace_regs =
*fregs)
> > > >  {
> > > > - unsigned long addr;
> > > > + unsigned long addr =3D ops->direct_call;
> > >
> > > nice, should it be read with READ_ONCE ?
> >
> > Is there a "read tearing" too?
>
> don't know, saw the comment in __modify_ftrace_direct and got curious
> why it's not in here.. feel free to ignore, I'll look it up
>
> jirka

Mhh, that's a good question. Based on my current understanding, it
seems that it should have a READ_ONCE, indeed. However, I'd like Mark
to confirm/deny this. :)

If this should be a READ_ONCE, I can send a v2 series with this fixed.