Diffstat (limited to 'Documentation/memory-barriers.txt')
1 files changed, 10 insertions, 6 deletions
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index ec3b5865c1be..7146da061693 100644
@@ -1868,12 +1868,16 @@ There are some more advanced barrier functions:
- These are for use with atomic (such as add, subtract, increment and
- decrement) functions that don't return a value, especially when used for
- reference counting. These functions do not imply memory barriers.
- These are also used for atomic bitop functions that do not return a
- value (such as set_bit and clear_bit).
+ These are for use with atomic RMW functions that do not imply memory
+ barriers, but where the code needs a memory barrier. Examples for atomic
+ RMW functions that do not imply are memory barrier are e.g. add,
+ subtract, (failed) conditional operations, _relaxed functions,
+ but not atomic_read or atomic_set. A common example where a memory
+ barrier may be required is when atomic ops are used for reference
+ These are also used for atomic RMW bitop functions that do not imply a
+ memory barrier (such as set_bit and clear_bit).
As an example, consider a piece of code that marks an object as being dead
and then decrements the object's reference count: