nanosleep returns 0 or -1 not the error code.
The error code "EINTR" (if encountered) is placed in errno, in which case nanosleep can be safely recalled with the remaining time.
This is required, so that nanosleep continues if the calling thread is interrupted by a signal.
See manpage nanosleep(2) for additional details.
(cherry picked from commit 1107c7f327)
c7f2f9fa1f