path: root/Documentation/RCU/rcu_dereference.txt
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Diffstat (limited to 'Documentation/RCU/rcu_dereference.txt')
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/RCU/rcu_dereference.txt b/Documentation/RCU/rcu_dereference.txt
index c0bf2441a2ba..b2a613f16d74 100644
--- a/Documentation/RCU/rcu_dereference.txt
+++ b/Documentation/RCU/rcu_dereference.txt
@@ -138,6 +138,15 @@ o Be very careful about comparing pointers obtained from
This sort of comparison occurs frequently when scanning
RCU-protected circular linked lists.
+ Note that if checks for being within an RCU read-side
+ critical section are not required and the pointer is never
+ dereferenced, rcu_access_pointer() should be used in place
+ of rcu_dereference(). The rcu_access_pointer() primitive
+ does not require an enclosing read-side critical section,
+ and also omits the smp_read_barrier_depends() included in
+ rcu_dereference(), which in turn should provide a small
+ performance gain in some CPUs (e.g., the DEC Alpha).
o The comparison is against a pointer that references memory
that was initialized "a long time ago." The reason
this is safe is that even if misordering occurs, the