You’ve probably heard of Mars Pathfinder, the NASA lander and its Sojourner rover that took up residence on Mars in 1997. At first, all was well, but after a few …. Mars Pathfinder: What Really Happened.
At first, all was well, but after a few days, the lander suffered a series of total system resets. A watchdog timer detected a problem and forced reboots. [Vivek Bhageria’s] recent post looks into what happened and the eventual solution.
This happens when a lower-priority task holds a resource needed by a higher-priority task and prevents the higher-priority task from executing. In this case, the operating system was VxWorks, but this can happen on any kind of priority scheduling system. The simplified version is that there were two tasks that each used the same mutex to avoid stepping on each other.
The highest priority was a data distribution task.
