Data multiprocessing system having protection against lockout of shared data
AssigneeNippon Electric Co., Ltd.
InventorSaburo Ohtaki
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Abstract
A data multiprocessing system has use-status word control circuitry for managing the exclusive use by individual processors one at a time of the common data resources of a shared main memory unit. To avoid the "system down" that occurs when a processor having exclusive use of such a common resource becomes inoperative, the control circuits of a still operative processor seeking to use that common resource will set the use-status words associated with the common resource back to a usable state thereby permitting that resource to be used by the operative processor.
Claims7
A data multiprocessing system comprising a plurality of processors, a main memory unit for storing at least one common resource exclusively usable by each processor one at a time and for also storing use-status words corresponding to the common resource and having contents for indicating the usable or unusable state of the common resource wherein a processor rewrites into the unusable state the contents of the use-status word read out when said use-status word read out indicates the usable state of that common resource, and wherein the processor is inhibited from using the common resource corresponding to the status word when said use-status word read out indicates the unusable state of that common resource, each processor comprising:
- means for changing the contents of a use-status word corresponding to a common resource into the unusable state when said data processor uses that common resource;
- means associated with said changing means for storing in a memory area data representing said processor associated with the corresponding use-status word;
- reporting means responsive to an inoperative condition of said processor for reporting by way of a signal to another processor that said processor has become inoperative;
- data preparing means responsive to an inoperative state-reporting signal received from another one of said processors to prepare data representing said one other processor;
- means for comparing the processor-representing data produced from said data preparing means with processor-representing data stored by the storing means of said one other processor to detect coincidence therebetween and produce a signal corresponding to said coincidence;
- and
- means responsive to said coincidence signal produced from said comparing means for changing the contents of the corresponding use-status word into the usable state.
A multiprocessing system comprising a plurality of processors, a memory unit for storing data as a common resource available for exclusive use by one processor at a time and for storing use-status information indicative of whether or not said common resource is currently being used by one of said processors, said processors being constructed to receive said common resource data only when the use-status information corresponding thereto is set to indicate a usable state, means connected to said one of said processors for setting said use-status information to indicate a nonusable state when said one of said processors begins use of said common resource and for setting said use-status information to indicate a usable-resource state when said one of said processors completes use of said common resource, and means connected to at least one other of said processors for setting said use-status information back to indicating a usable-resource state when a processor using said common resource has become inoperative.
Dependencies are inferred from the claim text.