The key change is to never return STATUS_TIMEOUT, and to instead return the result of NtYieldExecution() if zero timeout was passed, or STATUS_SUCCESS otherwise.
An overview of the correct values for each combination, copied from the test commit: - Non-alertable, zero timeout: STATUS_SUCCESS or STATUS_NO_YIELD_PERFORMED - Non-alertable, non-zero timeout: STATUS_SUCCESS - Alertable, zero timeout: STATUS_SUCCESS, STATUS_NO_YIELD_PERFORMED, or STATUS_USER_APC - Alertable, non-zero timeout: STATUS_SUCCESS or STATUS_USER_APC
-- v4: ntdll: Fix the return value of NtDelayExecution. ntdll/tests: Add tests for NtDelayExecution and Sleep(Ex).