The pthread_cond_clockwait() function shall be equivalent to pthread_cond_wait(), except that an error is returned if the absolute time specified by abstime as measured against the clock indicated by clock_id passes (that is, the current time measured by that clock equals or exceeds abstime) before the condition cond is signaled or broadcasted, or if the absolute time specified by abstime has already been passed at the time of the call. Implementations shall support passing CLOCK_REALTIME and CLOCK_MONOTONIC to pthread_cond_clockwait() as the clock_id argument. When such timeouts occur...[keep final sentence from existing paragraph.]

The pthread_cond_timedwait() function shall be equivalent to pthread_cond_clockwait(), except that it lacks the clock_id argument. The clock to measure abstime against shall instead come from the condition variable's clock attribute which can be set by pthread_condattr_setclock() prior to the condition variable's creation. If no clock attribute has been set, the default shall be CLOCK_REALTIME.