Asynchronous channel error mechanism

Claim 1

In channel error logging apparatus for a computer system having an addressable storage for storing an input/output (I/O) event stack with the capacity to store a plurality of I/O events, a central processing unit (CPU) for retrieving I/O events from the I/O event stack in storage and for processing said I/O events where the retrieving and processing of said I/O events from said I/O event stack is performed by said CPU asynchronously to the placement of said I/O events on the I/O event stack, a plurality of I/O adapters connected to control I/O devices, a channel connecting the plurality of I/O adapters to the CPU and the storage, said channel including polling means for polling said I/O adapters on a priority basis for service requirements, said polling means, upon finding an I/O adapter requiring service, halting polling of other I/O adapters until released by the channel upon completion of servicing of the I/O adapter requiring service, and a plurality of I/O registers accessible by the channel and the CPU, wherein each register is individually identifiable and where at least one I/O register contains an address for addressing said I/O event stack and where other I/O registers are used in association with an I/O adapter to maintain command and data addresses for performing an I/O operation, the improvement comprising: means for selectively giving said CPU or said channel access to said at least one I/O register which contains an address usable by said CPU or said channel for addressing the I/O event stack to store or retrieve a channel error I/O event on said stack; means in said channel for indicating the occurrence and type of channel errors occurring in the channel and in the plurality of I/O adapters in connection with an I/O operation; means responsive to the means for indicating the occurrence and type of channel errors for forming a channel error I/O event, said event including, a channel function field for identifying the type of I/O operation being performed at the occurrence of the channel error, a first identification field for identifying the I/O register in use at the occurrence of the channel error, a second identification field for identifying the I/O adapter using the channel at the occurrence of the channel error, and a third identification field for identifying the type of channel error which occurred; means for storing the formed channel error I/O event in the I/O event stack at a location in addressable storage designated by the contents of said at least one I/O register; and means responsive to the termination of a channel error I/O event storage operation for signalling said channel to release said polling means to resume normal polling and servicing of the I/O adapters, independently of the CPU retrieving the stored event from the I/O event stack, said CPU retrieving said stored I/O events asynchronously to the placement of said I/O events on said I/O event stack.