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Subject: Re: [PATCH v10 4/5] core: Add kernel message dumper to call on
	oopses and panics
From: Artem Bityutskiy <dedekind1@gmail.com>
To: Ingo Molnar <mingo@elte.hu>
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Date: Fri, 16 Oct 2009 14:00:28 +0300
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Cc: David Woodhouse <dwmw2@infradead.org>, LKML <linux-kernel@vger.kernel.org>,
	"Koskinen Aaro \(Nokia-D/Helsinki\)" <aaro.koskinen@nokia.com>,
	linux-mtd <linux-mtd@lists.infradead.org>,
	Simon Kagstrom <simon.kagstrom@netinsight.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>
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On Fri, 2009-10-16 at 12:10 +0200, Ingo Molnar wrote:
> * Simon Kagstrom <simon.kagstrom@netinsight.net> wrote:
> 
> > +int kmsg_dump_register(struct kmsg_dumper *dumper)
> > +{
> > +	unsigned long flags;
> > +
> > +	/* The dump callback needs to be set */
> > +	if (!dumper->dump)
> > +		return -EINVAL;
> > +
> > +	spin_lock_irqsave(&dump_list_lock, flags);
> > +
> > +	/* Don't allow registering multiple times */
> > +	if (dumper->registered) {
> > +		spin_unlock_irqrestore(&dump_list_lock, flags);
> > +
> > +		return -EBUSY;
> > +	}
> > +
> > +	dumper->registered = 1;
> > +	list_add(&dumper->list, &dump_list);
> > +	spin_unlock_irqrestore(&dump_list_lock, flags);
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(kmsg_dump_register);
> 
> 
> i dont want to bikeshed paint this but this sequence caught my eyes. We 
> generally do flatter and clearer locking sequences:
> 
> int kmsg_dump_register(struct kmsg_dumper *dumper)
> {
> 	unsigned long flags;
> 	int err = -EBUSY;
> 
> 	/* The dump callback needs to be set */
> 	if (!dumper->dump)
> 		return -EINVAL;
> 
> 	spin_lock_irqsave(&dump_list_lock, flags);
> 
> 	/* Don't allow registering multiple times */
> 	if (!dumper->registered) {
> 		dumper->registered = 1;
> 		list_add_tail(&dumper->list, &dump_list);
> 		err = 0;
> 	}
> 
> 	spin_unlock_irqrestore(&dump_list_lock, flags);
> 
> 	return err;
> }
> EXPORT_SYMBOL_GPL(kmsg_dump_register);

And while we are on it, I think these extra lines before and after
spinlocks are unneeded and even a bit annoying :-)

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)