In this guest editorial, TimeSys VP of Technology Doug Locke offers a rebuttal to Victor Yodaiken's recently published whitepaper on what's wrong with using a technique called 'priority inheritance' to avoid a problem in real-time systems known as 'priority inversion'. (Priority inversion is what caused big problems for the Mars Pathfinder Rover. It refers to the situation when a scheduled task must wait for a lower priority task to complete.) Locke writes . . .

“The technical arguments in [Yodaiken's] paper are not new, are generally correct, and have been widely discussed in the real-time research community for many years. However, the conclusions drawn in the paper are badly flawed.”

“Yodaiken's conclusions are drawn using the classic 'strawman' approach; the paper constructs an artificial hypothesis, and then shows that it might be dangerous. In this case his hypothesis is that priority inheritance is blindly used by engineers as a panacea for all priority inversion problems, and, because it has drawbacks under certain conditions, it is therefore dangerous and should never be used. In other words, because some carpenters might unsafely use a screwdriver to drive nails, screwdrivers should never be used . . .”

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