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-rw-r--r--Documentation/memory-barriers.txt12
1 files changed, 11 insertions, 1 deletions
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index 41ffd7e9cdcf..b5fe7657456e 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -1711,6 +1711,17 @@ There are some more advanced barrier functions:
operations" subsection for information on where to use these.
+ (*) lockless_dereference();
+ This can be thought of as a pointer-fetch wrapper around the
+ smp_read_barrier_depends() data-dependency barrier.
+
+ This is also similar to rcu_dereference(), but in cases where
+ object lifetime is handled by some mechanism other than RCU, for
+ example, when the objects removed only when the system goes down.
+ In addition, lockless_dereference() is used in some data structures
+ that can be used both with and without RCU.
+
+
(*) dma_wmb();
(*) dma_rmb();
@@ -1790,7 +1801,6 @@ The Linux kernel has a number of locking constructs:
(*) mutexes
(*) semaphores
(*) R/W semaphores
- (*) RCU
In all cases there are variants on "ACQUIRE" operations and "RELEASE" operations
for each construct. These operations all imply certain barriers: