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Subject: Re: [PATCH/RFC v5 4/5]: core: Add dump device to call on oopses
	and panics
From: Artem Bityutskiy <dedekind1@gmail.com>
To: =?ISO-8859-1?Q?J=F6rn?= Engel <joern@logfs.org>
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Date: Mon, 30 Nov 2009 09:27:51 +0200
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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>,
	Ingo Molnar <mingo@elte.hu>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
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On Thu, 2009-11-26 at 10:36 +0100, Jörn Engel wrote:
> Just stumbled across this patch.
> 
> On Tue, 13 October 2009 15:22:35 +0200, Simon Kagstrom wrote:
> > +void dump_kmsg(int panic)
> > +{
> > +	unsigned long len = ACCESS_ONCE(log_end);
> > +	struct dump_device *dump;
> > +	const char *s1, *s2;
> > +	unsigned long l1, l2;
> > +
> > +	s1 = "";
> > +	l1 = 0;
> > +	s2 = log_buf;
> > +	l2 = len;
> > +
> > +	/* Have we rotated around the circular buffer? */
> > +	if (len > log_buf_len) {
> 
> I believe this bit is wrong.  log_end is an unsigned int, so it can
> wrap relatively quickly.  If log_end just wrapped to 0 and dump_kmsg is
> called, the amount of printk buffer stored appears to be 0 as well.

To me it looks like 'log_end' is not supposed to wrap. What makes you
think it can? In which cases it can?

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)