With fastdebug builds an assertion failure is occurring when doing a Parker::park operation with a relative timeout, because cond_timed_wait is returning EINVAL indicating an invalid timespec. Inspection of the timespec structure shows the tv_nsec field has the value 1000000000 which is one more than the allowed maximum of 999999999.

In product builds this has the effect of causing a spurious unpark, but that can happen in any case and so higher-level code already accounts for it and so there is no harm.