Keywords: perfbook_html

### 14.2.4.2 Single-Variable Memory Consistency

If a group of CPUs all do concurrent stores to a single variable, the series of values seen by all CPUs will be consistent with at least one global ordering. For example, in the series of accesses shown in Figure , CPU 1 sees the sequence `{1,2}`, CPU 2 sees the sequence `{2}`, CPU 3 sees the sequence `{3,2}`, and CPU 4 sees the sequence `{4,2}`. This is consistent with the global sequence `{3,1,4,2}`, but also with all five of the other sequence of these four numbers that end in ``2''.

Had the CPUs used atomic operations (such as the Linux kernel's atomic_inc_return() primitive) rather than simple stores of unique values, their observations would be guaranteed to determine a single globally consistent sequence of values.