linux-kernel - Re: [PATCH -v5 00/17] Rewrite x86/ftrace to use text

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Message-ID: <CAADnVQJtNzyVrEy96tGhCiOfUEbLhzGzeF_7kXmS0SEG1=Upvg@mail.gmail.com>
Date:   Tue, 26 Nov 2019 21:01:06 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        bristot <bristot@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
        jbaron@...mai.com, Jessica Yu <jeyu@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, Nadav Amit <namit@...are.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        X86 ML <x86@...nel.org>
Subject: Re: [PATCH -v5 00/17] Rewrite x86/ftrace to use text_poke (and more)

On Tue, Nov 26, 2019 at 8:32 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Tue, Nov 26, 2019 at 4:03 PM Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
> >
> >
> >
> > On Tue, Nov 26, 2019 at 3:49 PM Masami Hiramatsu <mhiramat@...nel.org> wrote:
> >>
> >> On Tue, 26 Nov 2019 18:58:09 +0900
> >> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> >> > I applied following patch, but it seems not enough. While disabling 256 kprobes,
> >> > system was frozen (no BUG message).
> >>
> >> Aah, this is another bug in optprobe. I'll send a series for fix these bugs.
> >
> >
> > Awesome! I’ve started looking at this crash as well.
> > Could you share a brief description of the bug and cc me on fixes?
> > I’d like to test them too.
> > Thanks
>
> I noticed that your config doesn't have CONFIG_KPROBES_ON_FTRACE=y
> and without it most test.d/kprobe/ tests fail, but in your log they are passing.
> Also do you have KPROBE_EVENTS_ON_NOTRACE=y ?
> Since without these two configs the crash wasn't reproducing for me.
> Anyhow waiting for your fixes.

fwiw I bisected it down to commit 5b8ad1c9bc44 ("x86/kprobes: Fix
ordering while text-patching")
Reverting it fixes the crash. I bet Masami fix will be more correct.