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NNTP-Posting-Date: Wed, 06 Sep 2006 17:44:00 -0500
Newsgroups: comp.lang.ada
Subject: Re: Martian Rover Spirit's mulitasking software reset.
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From: Mark Lorenzen <mark.lorenzen@surfpost.dk>
Date: 06 Sep 2006 23:43:55 +0100
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Date: 2006-09-06T23:43:55+01:00
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Martin Dowie <martin.dowie@afraidof.co.uk> writes:

> ME wrote:
> > The mars rover Spirit suffered a software reset as a result of a
> > multitasking problem.
> > "The apparent cause was that the rover's central processing unit was
> > overworked as several tasks were running in parallel at the time."
> >  The rover uses VX works and I believe C. Testing obviously did not
> > catch this fault. Would the use of Ada  made any difference?
> >
> 
> My understanding is that there was a "priority inverstion", so had

That is also my understanding.

> they used "pragma Locking_Policy (Ceiling_Locking);" (RM  D.3 Priority
> Ceiling Locking) then the problem could have been avioded.
>
> Of course, they might not have used it even if they were using Ada. :-)

As far as I know, they were aware of the priority inversion problem
before launch, but did not consider it important enough to warrant a
fix. I guess that a watchdog device simply kicks in and reboots the
system, should it hang for too long.

- Mark