Abstract: Provides a method for increasing the connectivity of I/O resources to a multiplicity of operating systems (OSs) running in different resource partitions of a computer electronic complex (CEC) to obtain sharing of the I/O resources among the OSs of the CEC, including channels, subchannels (devices), and control units (CUs). The invention provides image identifiers (IIDs) for assigning resources to the different OSs. Each shared I/O resource has a sharing set of control blocks (CBs) in which a respective CB is assigned to (and located by) a respective IID of one of the OSs. Each of the CBs in a sharing set provides a different image of the same I/O resource. The different CB images are independently set to different states by I/O operations for the different OSs, so that the OSs can independently share the same I/O resource.

Abstract: A method for serializing access to computer system resources without disabling interrupts in critical code sections or requiring excessive use of spin locks. A queue lock is introduced that allows an interrupt process to enqueue and be processed in turn without a spin lock and to block process code access to a particular resource until all interrupts are processed. Process level code is blocked from accessing a locked resource while requests for accesses from interrupt level code are queued in a deferred work queue which is processed prior to the release of the blocking lock. Establishment of deferred work queue means that processing can continue without disablement of interrupts and without significant overhead consumed by processes holding spin locks.