Patent
1995-09-20
1997-09-02
Beausoliel, Jr., Robert W.
395288, G06F 1100
Patent
active
056640927
ABSTRACT:
A system and method for performing locked test and set cycles in a system having a plurality of interconnected buses, wherein one or more of the buses do not support locked test and set cycles. A CPU executing one or more processes is connected to one or more first buses that do not support locked test and set cycles. These one or more first buses are connected through a test and set device according to the present invention to one or more second buses which support locked test and set cycles. A memory is coupled to one of the one or more second buses that includes a semaphore bit shared by multiple threads or processes executing on the CPU. The test and set device performs locked test and set operations on the semaphore bit(s) in the memory at the direction of the thread executing on the CPU. A process or thread begins a test and set operation by setting a bit in a register in the test and set device then performing a read to the test and set device that maps to the target memory where the respective semaphore bit is located. In response to the read, the test and set device performs a locked read/write operation to the target memory using an atomic read/write protocol which locks out accesses from other processes. The test and set device then returns the read data obtained from the target memory semaphore bit to the CPU. The read cycle on the first bus is maintained until the test and set device has completed the test and set operations to the respective semaphore bit in the memory. In this manner, the one or more first buses are locked during the test and set operation, even where the one or more first buses do not inherently support test and set operations.
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Beausoliel, Jr. Robert W.
Hood Jeffrey C.
National Instruments Corporation
Palys Joseph E.
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