| While our bitmap_{}() functions are non-atomic, we have a number of operations |
| operating on single bits in a bitmap that are atomic. |
| The single bit operations are: |
| RMW atomic operations without return value: |
| RMW atomic operations with return value: |
| test_and_{set,clear,change}_bit() |
| smp_mb__{before,after}_atomic() |
| All RMW atomic operations have a '__' prefixed variant which is non-atomic. |
| In particular __clear_bit_unlock() suffers the same issue as atomic_set(), |
| which is why the generic version maps to clear_bit_unlock(), see atomic_t.txt. |
| The test_and_{}_bit() operations return the original value of the bit. |
| Like with atomic_t, the rule of thumb is: |
| - non-RMW operations are unordered; |
| - RMW operations that have no return value are unordered; |
| - RMW operations that have a return value are fully ordered. |
| Except for test_and_set_bit_lock() which has ACQUIRE semantics and |
| clear_bit_unlock() which has RELEASE 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. |