There is no code in nanosleep that converts it into a yield, and in fact a nanosleep(0) is a nanosleep(50µs) with the default timer slack value. If you want to yield, call sched_yield() …
I looked into this a bit further and it seems to be a range from [0,50]. [1] explains that if there is a pre-existing timer interrupt at 0, then the queue will be resumed at 0. But yes - given no other timers it will resume at 50.
