3.3. Hardware Considerations for Locks and Synchronization

Hardware-specific considerations must enter into the implementation of lock primitives on a system. The first consideration has to do with the processor's instruction set and the availability of machine instructions suitable for locking code. The second deals with the visibility of a lock's state when it is examined by executing kernel threads.

To understand how these considerations apply to lock primitives, keep in mind that a lock is a piece of data at a specific location in the system's memory. In its simplest form, a lock is a single byte location in RAM. A lock that is set, or held (has been acquired), is represented by all the bits in the lock byte being 1's (lock value 0xFF). A ...

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