linux-kernel - Re: [PATCH/RFC v5 4/5]: core: Add dump device to call on oopses and panics

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Date:	Mon, 30 Nov 2009 11:09:47 +0200
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	Jörn Engel <joern@...fs.org>
Cc:	Simon Kagstrom <simon.kagstrom@...insight.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-mtd <linux-mtd@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Koskinen Aaro (Nokia-D/Helsinki)" <aaro.koskinen@...ia.com>,
	Ingo Molnar <mingo@...e.hu>,
	David Woodhouse <dwmw2@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH/RFC v5 4/5]: core: Add dump device to call on oopses
 and panics

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.

Simon, if you want your patches to be merged to 2.6.33, we should
address this issue ASAP, otherwise it'll be too late.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)

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