linux-kernel - Re: Linux 6.1-rc3

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Message-ID: <CANiq72nfpdhPgEgWbz2T7C3GOk94mPbcqfvXTp3Lp=qRvtON9g@mail.gmail.com>
Date:   Tue, 1 Nov 2022 19:19:18 +0100
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>
Subject: Re: Linux 6.1-rc3

On Tue, Nov 1, 2022 at 6:58 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> Linker-generated symbols are usually the cause, but those tend to
> be fixed with the extra pass, and Guenter said that doing an extra
> pass does not avoid the issue here.

I have been trying to reproduce the issue on my side, trying to match
Guenter's environment, but so far I have not been successful, even
when running the toolchain binaries he sent me (thanks a lot!).

What I could reproduce easily, though, was one from the kernel test
robot, powerpc as well, in 5.15.y [1] It requires 4 passes (i.e.
KALLSYMS_EXTRA_PASS is not enough), but it is not an oscillating one.

[1] https://lore.kernel.org/lkml/202209241418.35P6OMjS-lkp@intel.com/

> What I've done in the past to debug this was to change
> scripts/link-vmlinux.sh to use a larger number of steps,
> mainly to see if it eventually converges, grows indefinitely
> or oscillates.

Does that mean you saw the oscillating one in the past? Guenter thinks
it is a new issue, since he never saw the oscillating case.

If you did see it, then it may be the case that the kallsyms changes
make some edge case more likely -- at least this is what Boqun and I
originally thought.

Cheers,
Miguel