linux-kernel - Re: [PATCH 2/5] of: dynamic: Refactor action prints to not use "%pOF" inside devtree

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Date:   Wed, 2 Aug 2023 15:33:21 -0600
From:   Rob Herring <robh@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Frank Rowand <frowand.list@...il.com>,
        "Enrico Weigelt, metux IT consult" <info@...ux.net>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Petr Mladek <pmladek@...e.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] of: dynamic: Refactor action prints to not use "%pOF"
 inside devtree_lock

On Tue, Aug 1, 2023 at 9:35 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Wed, Aug 02, 2023 at 06:28:48AM +0300, Andy Shevchenko wrote:
> > On Tue, Aug 01, 2023 at 03:54:45PM -0600, Rob Herring wrote:
> > > While originally it was fine to format strings using "%pOF" while
> > > holding devtree_lock, this now causes a deadlock.  Lockdep reports:
> > >
> > >     of_get_parent from of_fwnode_get_parent+0x18/0x24
> > >     ^^^^^^^^^^^^^
> > >     of_fwnode_get_parent from fwnode_count_parents+0xc/0x28
> > >     fwnode_count_parents from fwnode_full_name_string+0x18/0xac
> > >     fwnode_full_name_string from device_node_string+0x1a0/0x404
> > >     device_node_string from pointer+0x3c0/0x534
> > >     pointer from vsnprintf+0x248/0x36c
> > >     vsnprintf from vprintk_store+0x130/0x3b4
> > >
> > > To fix this, move the printing in __of_changeset_entry_apply() outside the
> > > lock. As there's already similar printing of the same changeset actions,
> > > refactor all of them to use a common action print function. This has the
> > > side benefit of getting rid of some ifdefs.
>
> ...
>
> > > v3:
> > >  - Add missing 'static' reported by 0-day
> >
> > It reported two issues (at least what I see).

Indeed. I missed the 2nd one.

> ...
>
> > > +   if (pr_debug("notify "))
> >
> > This is weird. How did you compile it?

I agree it's a weird pattern...

> Urgh, you need to fix dynamic debug macros to return an error code.

Or adding a 'pr_debug_cont' macro would do it. I'm inclined to wrap it
in an "#ifdef DEBUG" and be done with it.

Rob