linux-kernel - RE: small dmesg regression in kernel 4.17.3

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Date:   Thu, 28 Jun 2018 22:13:54 +0000
From:   "Schmauss, Erik" <erik.schmauss@...el.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Toralf Förster <toralf.foerster@....de>,
        "Moore, Robert" <robert.moore@...el.com>
CC:     ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: RE: small dmesg regression in kernel 4.17.3



> -----Original Message-----
> From: Andy Shevchenko [mailto:andy.shevchenko@...il.com]
> Sent: Wednesday, June 27, 2018 10:29 AM
> To: Toralf Förster <toralf.foerster@....de>; Schmauss, Erik
> <erik.schmauss@...el.com>
> Cc: ACPI Devel Maling List <linux-acpi@...r.kernel.org>; Linux Kernel <linux-
> kernel@...r.kernel.org>
> Subject: Re: small dmesg regression in kernel 4.17.3
> 
> +Cc: Erik
> 
> On Tue, Jun 26, 2018 at 8:57 PM, Toralf Förster <toralf.foerster@....de>
> wrote:
> > The attached dmesg contains non printable chars 0x01 33 around "ACPI
> > BIOS Error (bug): Could not resolve" which is a new issue compared to
> > the dmesg of 4.17.2
> >
> > System is a stable hardened Gentoo Linux at a ThinkPad T440s.
> 
> I bet the below commit makes this.
> 
> commit 2e78935d1e27d31955ad2dad4abe6c453cf669fd
> Author: Erik Schmauss <erik.schmauss@...el.com>
> Date:   Fri Jun 1 12:06:43 2018 -0700
> 
>    ACPICA: AML parser: attempt to continue loading table after error
> 
> 
Hi Andy,

> So, it does add leading '\n' which flushes buffers followed by printing the
> message you see. But, I'm guessing now, kernel adds a default level since it's
> going to dmesg which you can see as unprintable symbols.

What do you mean by a default level?

> Personally I'm not a fan of leading '\n':s since it brings more pain than fixing
> something. It has special meaning (flushing buffers) and many developers forget
> this.

This leading '\n' made it in Linux kernel unintentionally. It was originally intended as a change for acpiexec and it makes the dmesg look strange. I'll send out a fix.

Thanks for reporting it,

Erik
> 
> --
> With Best Regards,
> Andy Shevchenko