(Usually RAM; could be files or other forms of "memory")
Producer: overwrite memory, starting from the “top”, with numbers given to
you in sorted order.
412 18 17 411 414 413 415 50 54
Consumer: Return the median value (ideally 411)
==> Problem: Consumer consumes before producer is done producing! (Race condition)
for ( int i = 1000; i < 1012; i++ )
memory[i] = nn
==> Problem: Processes are overwriting each other; need synchronization, “atomic” operations
A: ... b = x + (5 * x); ...
B: ... x = z + (3 * z); ...
(variation of example from Wikipedia article on critical sections)
==> Problem: A might get two different values of x!
Get resource A
Get resource B
Do something with them
Put result in resource C
Release resources
|
Get resource B
Get resource A
Do something with them
Put result in resource D
Release resources
|
==> Example: 4 cars arrive at 4-way Stop Sign at the same time