linux-kernel - Re: [PATCH] gpio: Drop CONFIG_DEBUG

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CA+ASDXPncB=edDfXqkmWMqToQSt85UkAMzoApgyQATROoR1x9g@mail.gmail.com>
Date:   Tue, 22 Mar 2022 09:31:01 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>,
        Linus Walleij <linus.walleij@...aro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Jianqun Xu <jay.xu@...k-chips.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: Drop CONFIG_DEBUG_GPIO

On Tue, Mar 22, 2022 at 8:00 AM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
> On Tue, Mar 22, 2022 at 4:49 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
> > On Tue, Mar 22, 2022 at 3:38 PM Andy Shevchenko
> > <andy.shevchenko@...il.com> wrote:
> > > On Fri, Mar 11, 2022 at 4:55 AM Brian Norris <briannorris@...omium.org> wrote:
> > >
> > > ...
> > >
> > > > Description: it says nothing about enabling extra printk()s. But -DDEBUG
> > > > does just that; it turns on every dev_dbg()/pr_debug() that would
> > > > otherwise be silent.
> > >
> > > Which is what some and I are using a lot during development.

Well, we could fix that part by updating the documentation, so users
know what they're getting themselves into.

I'm also curious: does dynamic debug not suit you?
https://www.kernel.org/doc/html/v4.19/admin-guide/dynamic-debug-howto.html
TBH, I never remember its syntax, and it seems very easy to get wrong,
so I often throw in #define's myself, if I want it foolproof. But I'm
curious others thoughts too.

> > AFAIK this: https://www.kernel.org/doc/local/pr_debug.txt is the right
> > way to do it?
>
> Yes. But it means we need to have a separate option on a per driver
> (or group of drivers) basis. I don't think it's a good idea right now.

I'm not sure I understand this thought; isn't this the opposite of
what you're arguing above? (That drivers/gpio/ deserves its own
Kconfig option for enabling (non-dynamic) debug prints?)

> > https://www.kernel.org/doc/local/pr_debug.txt
> >
> > This doesn't mention adding Kconfig options just to enable debug messages.
> >
> > > ...
> > >
> > > > -ccflags-$(CONFIG_DEBUG_GPIO)   += -DDEBUG
> > > > -
> > >
> > > NAK to this change.
> > >
> > > I'm not against enabling might_sleep() unconditionally.
> > >
> >
> > These are already controlled by CONFIG_DEBUG_ATOMIC_SLEEP, no? Or
> > maybe I can't parse that double negation.
>
> The part of the patch that converts might_sleep_if():s is fine with me.

I'm fine with that approach (keep CONFIG_DEBUG_GPIO *only* as a
print-verbosity/DDEBUG control), even if I think it's a bit odd. My
main point in the patch is differentiating debug checks (that I want;
that are silent-by-default; that have their own Kconfig knobs) from
debug prints (that are noisy by default; that I don't want). So if you
convince Bartosz and/or Linus, you can get an Ack from me for a
partial revert.

Regards,
Brian