linux-kernel - Re: [PATCH] kgdb: fix gcc-11 warning on indentation

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Date:   Mon, 22 Mar 2021 19:18:53 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...e.hu>,
        Christian Brauner <christian.brauner@...ntu.com>,
        kgdb-bugreport@...ts.sourceforge.net,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kgdb: fix gcc-11 warning on indentation

On Mon, Mar 22, 2021 at 6:07 PM Doug Anderson <dianders@...omium.org> wrote:
> On Mon, Mar 22, 2021 at 9:43 AM Arnd Bergmann <arnd@...nel.org> wrote:
> >
> > -#define v1printk(a...) do { \
> > -       if (verbose) \
> > -               printk(KERN_INFO a); \
> > -       } while (0)
> > -#define v2printk(a...) do { \
> > -       if (verbose > 1) \
> > -               printk(KERN_INFO a); \
> > -               touch_nmi_watchdog();   \
> > -       } while (0)
> > -#define eprintk(a...) do { \
> > -               printk(KERN_ERR a); \
> > -               WARN_ON(1); \
> > -       } while (0)
> > +#define v1printk(a...) do {            \
>
> nit: In addition to the indentation change you're also lining up the
> backslashes. Is that just personal preference, or is there some
> official recommendation in the kernel? I don't really have a strong
> opinion either way (IMO each style has its advantages).

I don't think there is an official recommendation, I just think the
style is more common, and it helped my figure out what the
indentation should look like in this case.

>
> > +       if (verbose)                    \
> > +               printk(KERN_INFO a);    \
> > +} while (0)
> > +#define v2printk(a...) do {            \
> > +       if (verbose > 1)                \
> > +               printk(KERN_INFO a);    \
> > +       touch_nmi_watchdog();           \
>
> This touch_nmi_watchdog() is pretty wonky. I guess maybe the
> assumption is that the "verbose level 2" prints are so chatty that the
> printing might prevent us from touching the NMI watchdog in the way
> that we normally do and thus we need an extra one here?
>
> ...but, in that case, I think the old code was _wrong_ and that the
> intention was that the touch_nmi_watchdog() should only be if "verose
> > 1" as the indentation implied. There doesn't feel like a reason to
> touch the watchdog if we're not doing anything slow.

No idea. It was like this in Jason's original version from 2008.

        Arnd