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School of Computer Science & Engineering
University of New South Wales
 Advanced Operating Systems 
 COMP9242 2002/S2 

Effects of Memory Architecture

Example: end of a critical section

/* counter++; */
load	r1, counter
add	r1, r1, 1
store	r1, counter
/* unlock(mutex); */
store	zero, mutex

Relies on all CPUs seeing update of counter before update of mutex.

• Depends on proper ordering of stores to memory.