I would prefer to reuse pytime.c conversion code which is well tested by test_time. _PyTime_FromObject() already contains code to convert a double to _PyTime_t, and _PyTime_AsTimeval() converts a _PyTime_t to timeval. Use _PyTime_ROUND_CEILING as signal.sigtimedwait().

For signal.sigtimedwait(): see commit 34dc0f46ae5c0c9ec91d9402fac61111b802855f and http://bugs.python.org/issue22117.

Using ROUND_CEILING is now also used in the select module for a similar reason.

See my https://haypo.github.io/pytime.html article for the horror story of timestamp rounding :-)