linux-kernel - Re: [RFC][PATCH 6/7] printk: Poke printk extra hard

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Date:	Thu, 22 Dec 2011 09:43:33 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ted Ts'o <tytso@....edu>, Greg KH <greg@...ah.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	akpm@...ux-foundation.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 6/7] printk: Poke printk extra hard

On Thu, 2011-12-22 at 08:02 +0100, Ingo Molnar wrote:
> * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
> > On Wed, Dec 21, 2011 at 2:57 AM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> > >
> > >
> > > +#ifdef CONFIG_PRINTK_DEBUG
> > > +void printk_init(void)
> > > +{
> > > +       struct rq *rq;
> > > +       unsigned long flags;
> > > +
> > > +       local_irq_save(flags);
> > > +       rq = this_rq();
> > > +       raw_spin_lock(&rq->lock);
> > > +       printk(KERN_DEBUG "printk: echo echo echo..\n");
> > > +       raw_spin_unlock(&rq->lock);
> > > +       local_irq_restore(flags);
> > 
> > Ok, I can't really say that I think this is worth a config option like this.
> > 
> > Maybe an example module or something?

I really really really don't want to expose struct rq to modules, that's
just asking for trouble. But yeah, I know what you mean with not being
worth the config option, but then, I thought I might as well post it, it
can't be more horrible than the sem patch, can it ;-)

> > And I don't know *why*, but my immediate reaction to the 
> > message was that it either should be serious and say what it 
> > tested ("printk() works under rq lock"), or it should say 
> > "Bork bork bork". "echo echo echo" sounds just stupid.
> 
> We could perhaps use the standard mike test message:
> 
>   printk: Tap, tap, is this thing on?

Yeah, I clearly wasn't creative enough, I'm tempted to go with Linus'
suggestion though.
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