- RMW operations that have a return value are fully ordered.
- - RMW operations that are conditional are unordered on FAILURE,
- otherwise the above rules apply. In the case of test_and_set_bit_lock(),
- if the bit in memory is unchanged by the operation then it is deemed to have
- failed.
+ - RMW operations that are conditional are fully ordered.
-Except for a successful test_and_set_bit_lock() which has ACQUIRE semantics and
-clear_bit_unlock() which has RELEASE semantics.
+Except for a successful test_and_set_bit_lock() which has ACQUIRE semantics,
+clear_bit_unlock() which has RELEASE semantics and test_bit_acquire which has
+ACQUIRE semantics.
Since a platform only has a single means of achieving atomic operations
the same barriers as for atomic_t are used, see atomic_t.txt.