[js2]

That’s good to know. Indeed, the Pathfinder’s OS (VxWorks) had priority inheritance but it wasn’t enabled on a particular mutex and enabling it was the fix.

Priority inversion had been known about since the 70s. Priority inheritance seems to have first been proposed in 1990:

https://www3.nd.edu/~dwang5/courses/spring18/papers/real-tim... (Priority Inheritance Protocols: An Approach to Real-Time Synchronization)

The Pathfinder engineers were apparently unaware of the priority inheritance option available in VxWorks until they had to debug the issue live from a few hundred million km away.