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Subject: Re: [RFC][PATCH 6/7] printk: Poke printk extra hard
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, "Ted Ts'o" <tytso@mit.edu>,
        Greg KH <greg@kroah.com>, Thomas Gleixner <tglx@linutronix.de>,
        akpm@linux-foundation.org, linux-kernel <linux-kernel@vger.kernel.org>
Date: Thu, 22 Dec 2011 09:43:33 +0100
In-Reply-To: <20111222070212.GA9593@elte.hu>
References: <20111221105739.798864333@chello.nl>
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On Thu, 2011-12-22 at 08:02 +0100, Ingo Molnar wrote:
> * Linus Torvalds <torvalds@linux-foundation.org> wrote:
> 
> > On Wed, Dec 21, 2011 at 2:57 AM, Peter Zijlstra <a.p.zijlstra@chello.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.