linux-kernel - Re: [2/3] 2.6.22-rc2: known regressions v2

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Date:	Fri, 25 May 2007 10:19:52 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
cc:	Chris Newport <crn@...unix.com>, Ingo Molnar <mingo@...e.hu>,
	Christoph Lameter <clameter@....com>,
	Michal Piotrowski <michal.k.k.piotrowski@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Cherwin R. Nooitmeer" <cherwin@...il.com>,
	linux-pcmcia@...ts.infradead.org,
	Robert de Rooy <robert.de.rooy@...il.com>,
	Alan Cox <alan@...hat.com>, Tejun Heo <htejun@...il.com>,
	sparclinux@...r.kernel.org, David Miller <davem@...emloft.net>,
	Mikael Pettersson <mikpe@...uu.se>,
	linux1394-devel@...ts.sourceforge.net,
	Stefan Richter <stefanr@...6.in-berlin.de>,
	Kristian H?gsberg <krh@...planet.net>,
	linux-pm@...ts.linux-foundation.org,
	"Rafael J. Wysocki" <rjw@...k.pl>, Pavel Machek <pavel@....cz>,
	Marcus Better <marcus@...ter.se>,
	Andrey Borzenkov <arvidjaar@...l.ru>,
	linux-usb-devel@...ts.sourceforge.net,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: [2/3] 2.6.22-rc2: known regressions v2

On Fri, 25 May 2007, Alan Cox wrote:
> 
> There is an additional factor - dumps contain data which variously is -
> copyright third parties, protected by privacy laws, just personally
> private, security sensitive (eg browser history) and so on.

Yes. 

I'm sure we've had one or two crashdumps over the years that have actually 
clarified a bug.

But I seriously doubt it is more than a handful. 

> Diskdump (and even more so netdump) are useful in the hands of a
> developer crashing their own box just like kgdb, but not in the the
> normal and rational end user response of  "its broken, hit reset"

Amen, brother.

Even for developers, I suspect a _lot_ of people end up doing "ok, let's 
bisect this" or some other method to narrow it down to a specific case, 
and then staring at the source code once they get to that point.

At least I hope so. Even in user space, you should generally use gdb to 
get a traceback and perhaps variable information, and then go look at the 
source code.

Yes, dumps can (in theory) be useful for one-off issues, but I doubt many 
people have ever been able to get anything much more out of them than from 
a kernel "oops" message. 

For developers, I can heartily recommend the firewire-based remote debug 
facilities that the PowerPC people use. I've used it once or twice, and it 
is fairly simple and much better than a full dump (adn it works even when 
the CPU is totally locked up, which is the best reason for using it).

But 99% of the time, the problem doesn't happen on a developer machine, 
and even if it does, 90% of the time you really just want the traceback 
and register info that you get out of an oops.

			Linus
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