Importance

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Abstract

Using a lockless protocol, readers and writers exchange data of arbitrary size without using operating system services other than to initially establish a region of global shared memory. The readers and writers may be in interrupt context, process context and/or thread context. Multiple readers and writers are permitted, on the same or on separate processors sharing a global memory. Writers own a set of buffers in global shared memory. The buffers are re-used by their owner using an LRU algorithm. New data is made available to readers by atomically writing the buffer ID (and sequence number) of the most recently written buffer into a shared location. Readers use this shared location to find the most recently written data. If a reader does not have sufficient priority to read the data in the buffer before a writer must re-use the buffer for subsequent data, the reader restarts its read. Buffers contain sequence numbers maintained by the writers to allow the readers to detect this 'slow read' situation and to restart its read using the most recently written buffer. Provisions are provided for data time stamps and for resolving ambiguity in the execution order of multiple writers that could cause time stamps to retrogress.

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First Claim