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Intel 64 and IA-32 Architectures Software Developer's Manual Volume
3A: System Programming Guide, Part 1
7.1.2.2 Software Controlled Bus Locking
Software should access semaphores (shared memory used for signalling
between multiple processors) using identical addresses *and operand lengths*.
For example, if one processor accesses a semaphore using a word access, other
processors should not access the semaphore using a byte access.
For more complete information about compiler optimizations, see our Optimization Notice.