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Message-ID: <CAMuHMdVV67se-DzG=aDL4Y7NsctNRbi0P2p-SSgG7kh0Ce4TOQ@mail.gmail.com>
Date: Thu, 7 Nov 2019 08:27:29 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Andy Whitcroft <apw@...onical.com>,
Joe Perches <joe@...ches.com>,
Dmitry Safonov <dima@...sta.com>,
Petr Mladek <pmladek@...e.com>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 00/50] Add log level to show_stack()
Hi Russell,
(reduced CC list)
On Thu, Nov 7, 2019 at 12:28 AM Russell King - ARM Linux admin
<linux@...linux.org.uk> wrote:
> On Wed, Nov 06, 2019 at 09:34:40PM +0100, Peter Zijlstra wrote:
> > I suppose I'm surprised there are backtraces that are not important.
> > Either badness happened and it needs printing, or the user asked for it
> > and it needs printing.
>
> Or utterly meaningless.
>
> > Perhaps we should be removing backtraces if they're not important
> > instead of allowing to print them as lower loglevels?
>
> Definitely! WARN_ON() is well overused - and as is typical, used
> without much thought. Bound to happen after Linus got shirty about
> BUG_ON() being over used. Everyone just grabbed the next nearest thing
> to assert().
Which is what checkpatch.pl suggests...
> As a kind of example, I've recently come across one WARN_ON() in a
> driver subsystem (that shall remain nameless at the moment) which very
> likely has multiple different devices on a platform. The WARN_ON()
> triggers as a result of a problem with the hardware, but because it's a
> WARN_ON(), you've no idea which device has a problem. The backtrace is
> mostly meaningless. So you know that a problem has occurred, but the
> kernel prints *useless* backtrace to let you know, and totally omits
> the *useful* information.
So that callsite should be converted to use dev_WARN(), with a suitable
message.
Perhaps checkpatch should be updated, to suggest {,dev_}WARN()
instead of WARN_ON(), and add a check for the latter, too?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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