Comments on “Generalized rate monotonic schedulability bounds using relative period ratios”

In this Letter, it is shown that the schedulability test method for task sets with the maximum period ratio larger than or equal to 2 presented in the paper [Wei et al., Generalized rate monotonic schedulability bounds using relative period ratios, Information Processing Letters 107 (5) (2008) 142–148] is not exactly correct by presenting a counter-example. Correct sufficient conditions for using period ratios in RM schedulability test when the maximum period ratio is not less than 2 are also presented.

Research highlights
► The previous generalized conditional bound for period ratio ⩾2 is too optimistic.
► We find three methods to obtain conditional bounds for period ratio ⩾2.
► A new method for calculating conditional bound with lower time complexity is presented.