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Il Simpatico è un'area libera di discussione, di scambio di idee e di aperto confronto sui temi che più ci appassionano: dal rinnovamento dell'Italia all'ultima novità del "gadgettismo", dalla filosofia alla musica, dal mondo dell'informatica e del web al global warming ... senza scordare frizzi, lazzi e curiosità da ogni angolo del globo !!!
RispondiEliminaSuch an event occurred on the Mars Pathfinder mission in July 1997. The Pathfinder mission is best known for the little rover that took high-resolution color pictures of the Martian surface and relayed them back to Earth.
The problem was not in the landing software, but in the mission software run on the Martian surface. In the spacecraft, various devices communicated over a MIL-STD-1553 data bus. Activity on this bus was managed by a pair of high-priority tasks. One of the bus manager tasks communicated through a pipe with a low-priority meteorological science task.
On Earth, the software mostly ran without incident. On Mars, however, a problem developed that was serious enough to trigger a series of software resets during the mission. The sequence of events leading to each reset began when the low-priority science task was preempted by a couple of medium-priority tasks while it held a mutex related to the pipe. While the low-priority task was preempted, the high-priority bus distribution manager tried to send more data to it over the same pipe. Because the mutex was still held by the science task, the bus distribution manager was made to wait. Shortly thereafter, the other bus scheduler became active. It noticed that the distribution manager hadn't completed its work for that bus cycle and forced a system reset.