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

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Message-ID: <alpine.LFD.0.98.0705250937550.26602@woody.linux-foundation.org>
Date:	Fri, 25 May 2007 09:45:28 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Chris Newport <crn@...unix.com>
cc:	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, Chris Newport wrote:
>
> Maybe we should take a hint from Solaris.

No. Solaris is shit. They make their decisions based on "we control the 
hardware" kind of setup.

> If the kernel crashes Solaris dumps core to swap and sets a flag.
> At the next boot this image is copied to /var/adm/crashdump where
> it is preserved for future debugging. Obviously swap needs to be
> larger than core, but this is usually the case.

(a) it's not necessarily the case at all on many systems

(b) _most_ crashes that are real BUG()'s (rather than WARN_ON()'s) leave 
    the system in such a fragile state that trying to write to disk is the 
    _last_ thing you should do.

    Linux does the right thing: it tries to not make bugs fatal. 
    Generally, you should see an oops, and things continue. Or a 
    WARN_ON(), and things continue. But you should avoid the "the machine 
    is now dead" cases.

(c) have you looked at the size of drivers lately? I'd argue that *most* 
    bugs by far happen in something driver-related, and most of our source 
    code is likely drivers.

    Writing to disk when the biggest problem is a driver to begin with 
    is INSANE.

So the fact is, Solaris is crap, and to a large degree Solaris is crap 
exactly _because_ it assumes that it runs in a "controlled environment".

Yes, in a controlled environment, dumping the whole memory image to disk 
may be the right thing to do. BUT: in a controlled environment, you'll 
never get the kind of usage that Linux gets. Why do you think Linux (and 
Windows, for that matter) took away a lot of the market from traditional 
UNIX? 

Answer: the traditional UNIX hardware/control model doesn't _work_. People 
want more flexibility, both on a hardware side and on a usage side. And 
once you have the flexibility, the "dump everything to disk" is simply not 
an option any more.

Disk dumps etc are options at things like wall street. But look at the bug 
reports, and ask yourself how many of them happen at Wall Street, and how 
many of them would even be _relevant_ to somebody there? 

So forget about it. The whole model is totally broken. We need to make 
bug-reports short and sweet, enough so that random people can 
copy-and-paste them into an email or take a digital photo. Anything else 
IS TOTALLY INSANE AND USELESS!

			Linus
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