linux-kernel - Re: lock in vsprintf(): was: Re: [PATCH] of: Add printf '%pOFm' for generating modalias

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Message-ID: <Z3aPSwnbUhqvp59v@pathway.suse.cz>
Date: Thu, 2 Jan 2025 14:06:39 +0100
From: Petr Mladek <pmladek@...e.com>
To: Rob Herring <robh@...nel.org>
Cc: John Ogness <john.ogness@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Jonathan Corbet <corbet@....net>,
	Saravana Kannan <saravanak@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Zijun Hu <quic_zijuhu@...cinc.com>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: lock in vsprintf(): was: Re: [PATCH] of: Add printf '%pOFm' for
 generating modalias

On Mon 2024-12-30 14:26:43, Rob Herring wrote:
> On Thu, Dec 19, 2024 at 08:17:21PM +0106, John Ogness wrote:
> > On 2024-12-19, Petr Mladek <pmladek@...e.com> wrote:
> > > I do not want to revert everything now just because of theoretical
> > > problems.
> > 
> > What would you revert? This has always been an issue for printk().
> > 
> > > Well, it would be nice to document the lock dependency in
> > > Documentation/core-api/printk-formats.rst
> > 
> > Yes. If any locking is involved at all, such specifiers should be
> > documented as not safe in NMI context or within printk_cpu_sync
> > blocks. 
> 
> For the folks that don't read documentation, should we bail out on 
> in_nmi() for these as well?

I like this idea.

Best Regards,
Petr