Subject: Re: [PATCH 2/2 -mm] fault-injection: lightweight code-coverage
	maximizer
From: Don Mullis <dwm@meer.net>
To: Akinobu Mita <akinobu.mita@gmail.com>
Cc: akpm <akpm@osdl.org>, lkml <linux-kernel@vger.kernel.org>
In-Reply-To: <20061128091811.GA2004@APFDCB5C>
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Date: Tue, 28 Nov 2006 12:14:36 -0800
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On Tue, 2006-11-28 at 18:18 +0900, Akinobu Mita wrote:
> On Mon, Nov 27, 2006 at 11:51:30PM -0800, Don Mullis wrote:
> > Upon keying in
> > 	echo 1 >probability
> > 	echo 3 >verbose
> > 	echo -1 >times
> > a few dozen stacks are printk'ed, then system responsiveness
> > recovers to normal.  Similarly, starting a non-trivial program
> > will print a few stacks before responsiveness recovers.
> 
> What kind of test did you do?

First, waiting a few seconds for the standard FC-6 daemons to wake up.
Then, Xemacs and Firefox.  Not tested on SMP.


> This doesn't maximize code coverage. It makes fault-injector reject
> any failures which have same stacktrace before.

Since the volume of (repeated) dumps is greatly reduced, 
interval/probability can be set more aggressively without crippling
interaction.  This increases the number of error recovery paths covered
per unit of wall clock time.


> Updating array in this way is not safe (SMP or interrupt).
 
You're right.  Patch forthcoming.

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