multiprocessing.Process opens a FIFO to the child. This FIFO is not documented the the Process class API and it's purpose is not clear from the documentation. It is a minor documentation bug that the class creates non-transparent resource utilization.

The primary behavioral bug is that incorrect handling of this FIFO creates a resource leak, since the file descriptor is not closed on join(), or even when the parent Process object goes out of scope.

The effect of this bug is that programs generating large numbers of Process objects will hit system resource limits of open file descriptors.