US Patent 7676618 Controlling resource transfers in a logically partitioned computer system

A resource and partition manager of the preferred embodiments includes a lock mechanism that operates on a plurality of locks that control access to individual I/O slots. The resource and partition manager uses the lock mechanism to obtain a lock on an I/O slot when transferring control of the I/O slot to a logical partition that is powering on and when removing the I/O slot from a logical partition that is powering off. The resource and partition manager uses the lock mechanism to remove control of an I/O slot from, or return control to, an operating logical partition in order to facilitate hardware service operations on that I/O slot or on the physical enclosure in which it is contained.