linux-kernel - Re: [mm 4.15-rc8] Random oopses under memory pressure.

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Message-ID: <CA+55aFyxyjN0Mqnz66B4a0R+uR8DdfxdMhcg5rJVi8LwnpSRfA@mail.gmail.com>
Date:   Tue, 16 Jan 2018 11:34:46 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Michal Hocko <mhocko@...nel.org>
Subject: Re: [mm 4.15-rc8] Random oopses under memory pressure.

On Tue, Jan 16, 2018 at 9:33 AM, Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
>
> Since I got a faster reproducer, I tried full bisection between 4.11 and 4.12-rc1.
> But I have no idea why bisection arrives at c0332694903a37cf.

I don't think your reproducer is 100% reliable.

And bisection is great because it's very aggressive and optimal when
it comes to testing. But that also implies that if *any* of the
good/bad choices were incorrect, then the end result is pure garbage
and isn't even *close* to the right commit.

> It turned out that CONFIG_FLATMEM was irrelevant. I just did not hit it.

So have you actually been able to see the problem with FLATMEM, or is
this based on the bisect? Because I really think the bisect is pretty
much guaranteed to be wrong.

               Linus