For linear system consideration, model the inverter as a nagative gain, and model the other blocks in the loop as what it is (transfer function). Make the loop open at the high impendence node (exp: input of the inverter); excite ac signal with bias voltage at input break node, measure the output at the other break node. If the gain at total phase shift at 360 is larger than 1, system may oscillate. On the otherhand, if you try to calculate close loop transfer function from all the noise nodes to the output, if the pole locations are the conjugate unstable poles, then system will oscillates.