linux-kernel - Re: Can printk() sleep at runtime?

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Message-ID: <152777998940.144038.2717154952249020053@swboyd.mtv.corp.google.com>
Date:   Thu, 31 May 2018 08:19:49 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Petr Mladek <pmladek@...e.com>
Cc:     baijiaju1990@...il.com, Bjorn Helgaas <bhelgaas@...gle.com>,
        SergeySenozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Corbet <corbet@....net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Michael Turquette <mturquette@...libre.com>
Subject: Re: Can printk() sleep at runtime?

Quoting Linus Torvalds (2018-05-31 07:32:10)
> On Thu, May 31, 2018 at 5:05 AM Petr Mladek <pmladek@...e.com> wrote:
> >
> > Anyway, we need to fix or remove this format. vsprintf-like functions
> > are called in any context and nobody expect that they might sleep.
> 
> Ack. I guess the argument is that "%pCr" is rare, and none of *those*
> users may care, but I do think that doing things wrong as-is.
> 
> It's too subtle to have to know you're in a particular locking context
> when you use a particular %p modifier.
> 

Agreed. Removing the format seems to be the best approach. It looks like
only Geert has used it in the last few years and it hasn't been used
much otherwise.