Comments on "The Model Checker SPIN"

The paper by G.J. Holzmann (see ibid., vol.23, no.5, p.279-95, 1997) describes how to apply SPIN to the verification of a synchronization algorithm (L.M. Ruane, 1990) in process scheduling of an operating system. We report an error in the verification model presented by G.J. Holzmann and present a revised model with verification result. Our result explains the reason why SPIN found the race condition in the synchronization algorithm. We also show that the suggested fix by G.J. Holzmann is incorrect.