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>> + if (unlikely(!start)) >> + start = NO_START_TIME; >> + } >> return start; > > > Oh, and actually, given you have `start > NO_START_TIME` condition in > exit function, you don't need this `if (unlikely(!start))` bit at all, > because you are going to ignore both 0 and 1. So maybe no need for a > new function, but no need for extra if as well. This unlikely(!start) is needed for very unlikely case when sched_clock() returns 0. In such case the prog should still be executed.